Introduction

New anticancer agents which combine effectiveness, safety, and convenience remain a challenge for the international science community. Currently, anticancer chemotherapy development is conducted through cytotoxic compounds identification, in other words, identifying those compounds capable of destroying cancer cells. Such agents improve the survival rates and quality of life of patients with tumors (Ismael et al. 2008; Narang and Desai 2009). The traditional cell line test screening model is a widely used tool due because of its easy manipulation, molecular characterization, and its high degree of specificity and reproducibility. Such trials are an exceptional means to study cellular pathways and the genes critically involved in cancer (Ferreira et al. 2013). In organic chemistry, due to their many applications, derivatives of thiophene stand out among bio-molecules used in trials to determine biological activity. They are present in natural products and are frequently incorporated into agrochemicals, dyes, and drugs in general (Mishra et al. 2011; Meotti et al. 2003; Chaudhary et al. 2012). Various thiophene derivatives are produced by molecular modifications through varied synthesis routes that result in increases in specificity and thus safety profiles (Mohammad et al. 2012; Wermuth 2011). Within the thiophenic family, the 2-amino-thiophenes have been well reported. In new drugs investigations they occupy a special position due to innovations in their synthesis (Gewald reaction), availability, stability, and structural simplicity that allow them to be important scaffolds in chemical and therapeutic products; like the top selling drugs Olanzepine and Tinoridine (Puterová et al. 2010; Huang et al. 2011; Liang et al. 2014). In addition, they present a large spectrum of biological properties that include antimicrobial (Arora et al. 2013; Rao et al. 2013), anti-inflammatory (Khan et al. 2006), anxiolytic (Fortes et al. 2013), antileishmanial (Rodrigues et al. 2015), anti-diabetes (Duffy et al. 2005), antifungal (Abo-Salem et al. 2014), antioxidant (Gouda et al. 2013), and antiplatelet activities (Jagadish et al. 2013).

Antitumor activity was also an evaluation target (El-Shorafa et al. 2015), on human cell lines of colorectal cancer (HT29), lung cancer (NCI H-292), and larynx carcinoma (HEP), in which thiophene derivatives were considered promising compounds with the potential of aiding in the discovery of new antitumor agents due to their significant anti-proliferative activity. Considering the importance of thiophene derivatives as seen in the literature, and given the preliminary positive results obtained by our research group (Mohareb et al. 2016) this work had, as its goal, to synthesis new 4,5-dihydrobenzo[b]thiophene derivatives using the Gewald’s thiophene synthesis (Aguiara et al. 2016) of cyclohexan-1,4-dione and cyanoacetanilide derivatives followed by measuring their cytotoxicity towards cancer cell lines, the anti-proliferative activities and measuring the inhibition of the most active compounds towards c-Met kinase.

Results and discussion

The reaction of cyclohexan-1,4-dione with the 2-cyano-N-arylacetamide derivatives 2a–c and elemental sulfur gave the 4,5-dihydrobenzo[b]thiophene derivatives 3a–c, respectively. The molecular structures of 3a–c compounds were based on their analytical and spectral data. Thus, the 1H nuclear magnetic resonance (NMR) spectrum of 3a showed the presence of a singlet at δ 8.28 ppm indicating the presence of the NH group, a multiplet at δ 7.38–7.26 ppm for the phenyl protons, a singlet at δ 4.85 ppm (D2O exchangeable) equivalent to the NH2 group, a singlet at δ 2.79 ppm for the two protons at C-8 and two triplets at δ 1.92–1.65 ppm for the four protons at C-4 and C-5. Moreover, the 13C NMR spectrum showed two signals at δ 166.2, 164.8 equivalent to the two CO groups, signals at δ 141.8, 140.2, 138.4, 133.5, 127.2, 124.8, 122.5, 120.5, 119.5 equivalent to the benzene carbons and the C-2, C-3, C-6a, and C-7b carbons and three signals at δ 40.0, 38.8, 18.6 equivalent to the C-4, C-5, C-7 carbons. The reaction of any of compounds 3a–c with any of the diazonium salts 4a–c gave the arylhydrazono derivatives 5a–i, respectively (Scheme 1).

Scheme 1
scheme 1

Synthesis of compounds 3a–c, 4a–c, and 5a–i

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Next we proposed a one-pot synthesis for thiazole-2(3H)-thione derivatives through the reaction of any of compounds 3a–c with elemental sulfur and phenylisothiocyanate (6). The reaction occurred in 1,4-dioxane containing a catalytic amount of triethylamine to give the dihydrothieno[2′,3′:3,4]benzo[1,2-d]thiazole-2(3H)-thione derivatives 7a–c, respectively. On the other hand, the reaction of any of compounds 3a-c with ethyl orthoformate gave the 7-ethoxymethyleno derivatives 9a–c, respectively. Their analytical and spectral data were consistent with their respective structures. Further reaction of any of compounds 9a–c with either of malononitrile (10a) or ethyl cyanoacetate (10b) gave the 2-amino-4H-thieno[2,3-f]chromene-8-carbonitrile derivatives 11a–f, respectively (Scheme 2). The reaction took place firstly through the simple condensation of the cyanomethylene reagent followed by intra-molecular cyclization.

Scheme 2
scheme 2

Synthesis of compounds 7a–c, 9a–c, and 11a–f

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The reaction of any of compounds 9a–c with either of hydrazine hydrate (12a) or phenyl hydrazine (12b) gave the 5,7-dihydro-thieno[2,3-e]indazol-2-amine derivatives 13a–f, respectively.

Recently, our research group was involved through comprehensive program for the reaction of active methylene compounds with phenylisothiocyanate in basic dimethylformamide to give intermediate potassium sulfide salt. Heterocyclization of the suphide salt with α-halocarbonyl compounds gave either thiazole or thiopene derivatives (Mohareb et al. 1999, 1995). As a continuation of this program the reaction of any of compounds 3a–c with phenylisothiocyanate (6) in DMF/KOH solution at room temperature gave the intermediate potassium sulfide salts 14a–c. The reaction of any of the latter salts with either of ethyl chloroacetate (15a) or chloroacetone (15b) gave the (3-phenylthiazol-2(3H)-ylidene)-4,5-dihydrobenzo[b]thiophene derivatives 16a–f, respectively (Scheme 3). The molecular structure of 16a–f was established on the basis of analytical and spectral data. Thus, the 1H NMR spectrum of 16a (as an example) showed the presence of two singlets at δ 10.02, 8.26 ppm (D2O exchangeable) for the OH and NH groups, a multiplet at δ 7.39–7.27 ppm for the two phenyl groups, a singlet at δ 6.08 ppm for the proton attached to C-5, a singlet at δ 4.84 ppm for the NH2 group and two triplets at δ 2.97–2.22 ppm for the four protons attached to C-4 and C-5. In addition, the 13C NMR spectrum showed two signals at δ165.8, 163.8 equivalent to the two CO groups, signals at δ 150.3, 144.8, 143.4, 141.9, 138.6, 136.3, 132.9 131.6, 130.8, 129.2, 128.5, 127.3, 125.8, 121.9, and 120.2 for the two benzene carbons, and the C-2, C-3, C-7, C-3a, C-7a, C-4′, and C-5′ carbons, signal at δ 106.9 indicating the C-7 carbon and two signals at δ 32.8, 20.4 for the C-4, C-5 carbons.

Scheme 3
scheme 3

Synthesis of compounds 13a–f and 16a–f

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Biology

HTRF kinase assay

It has been reported that the c-Met kinase activity correlated to the prostate cancer where the transformation of prostate cancer from the primary androgen-sensitive to the androgen-insensitive status along with the gain of radioresistance that signaling by the receptor tyrosine kinase (RTK) c-Met played a key role in it. Firstly, an inverse correlation between the expression of androgen receptor (AR) and c-Met has been observed in prostate epithelium, prostate cancer cells and Pim- kinase (Knudsen et al. 2002; Humphrey et al. 1995). Secondly, AR signaling suppressed c-Met transcription, while the removal of androgen increased c-Met expression (Verras et al. 2007). Thirdly, it is observed that c-Met expression is high in late stage and bone metastatic prostate cancer (Knudsen et al. 2002). Furthermore, a recent study has demonstrated that c-Met expression has a close relationship with the cellular radiosensitivity (Bacco et al. 2011). Based on these reported observations, we studied the activity of the synthesized compounds towards PC-3 prostate cancer cell line, results were demonstrated through Table 1. The c-Met kinase activity of all compounds was evaluated using homogeneous time-resolved fluorescence (HTRF) assay as previously reported (Tang et al. 2016; Liu et al. 2016). In addition, the most active compounds were further evaluated against other five tyrosin kinase (c-Kit, Flt-3, VEGFR-2, EGFR, and PDGFR) using the same screening method. Briefly, 20 lg/mL poly (Glu, Tyr) 4:1 (Sigma) was pre-coated as a substrate in 384-well plates. Then 50 lL of 10 mMATP (Invitrogen) solution diluted in kinase reaction buffer (50 mM HEPES, Ph 7.0, 1 M DTT, 1 M MgCl2, 1 M MnCl2, and 0.1% NaN3) was added to each well. Various concentrations of compounds diluted in 10 lL of 1% DMSO (v/v) were used as the negative control. The kinase reaction was initiated by the addition of purified tyrosine kinase proteins diluted in 39 mL of kinase reaction buffer solution. The incubation time for the reactions was 30 min at 25 °C and stopped by the addition of 5 mL of Streptavidin-XL665 and 5 μL Tk Antibody Cryptate working solution to all of wells. The plates were read using Envision (PerkinElmer) at 320 and 615 nM. The inhibition rate (%) was calculated using the following equation: % inhibition = 100 − [(Activity of enzyme with tested compounds − Min)/(Max−Min)] × 100 (Max: the observed enzyme activity measured in the presence of enzyme, substrates, and cofactors; Min: the observed enzyme activity in the presence of substrates, cofactors and in the absence of enzyme). IC50 values were calculated from the inhibition curves.

Table 1 c-Met enzymatic activity and anti-proliferative evaluation of target compounds against PC-3 cell line
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In vitro enzymatic assays

All newly synthesized thiophene derivatives were evaluated for their inhibitory activity toward c-Met enzyme using a HTRF assay. Taking foretinib as the positive control, the results expressed as IC50 were summarized in Table 1. The IC50 values are the average of at least three independent experiments. As illustrated in Table 1, all the tested compounds displayed potent c-Met enzymatic activity with IC50 values ranging from 0.32 to 40.32 nM. Compared with foretinib (IC50 = 1.16 nM).

Structure–activity relationship

As it is clear from Table 1, that most of the synthesized compounds showed high c-Met enzyme activities and high potency against the PC-3 cancer cell lines. For the dihydrobenzo[b]thiophen-6(7H)-one derivatives 3a–c, it is clear that these compounds showed moderate activities where compound 3c with X=NO2 showed the highest potency against c-Met kinase with IC50 8.39 nM and PC-3 cell line with IC50 6.29 nM. Considering the arylhydrazone derivatives 5a–i, most of these compounds gave excellent results excepting compound 5a (X=Y=H). Compounds 5d (X=Cl, Y=H), 5f (X=Cl, Y=OCH3), and 5h (X=NO2, Y=Cl) showed the highest activities toward c-Met kinase and PC-3 cell line. The reaction of compounds 3a–c with elemental sulfur and phenylisothiocyanate to afford compounds 7a–c showed remarkable increase of potency of these compounds. Thus, compounds 7b (X=Cl) and 7c (X=NO2) showed the highest potency against c-Met kinase and PC-3 cell line. The reaction of compounds 3a–c with ethyl orthoformate to give compounds 9a–c, showed similar potency like compounds 7a–c. The reaction of 9a–c with either of maononitrile or ethyl cyanoacetate gave the thieno[2,3-f]chromene derivatives 11a–f where compounds 11c (X=Cl, Y=NH2), 11d (X=Cl, Y=OH), and 11f (X=NO2, Y=OH) showed the highest potency against c-Met kinase and PC-3 cell line. Regarding the reactivity of the thieno[2,3-e]indazole derivatives 13a–f, these compounds exhibited from weak to moderate potency where compounds 13a, 13b, and 1b showed week potency while compounds 13c (X=Cl, R=H), 13e (X=NO2, R=H), and 13f (X=NO2, R=Ph) showed moderate potencies. It is obvious that compound 13f showed highest potency against c-Met kinase with IC50 2.63 nM while it showed low potency against PC- cell line with IC50 6.19 nM. Finally, for the thiazol-2(3H)-ylidene)-4,5-dihydrobenzo[b]thiophene derivatives 16a–f, compound 16d (X=Cl, Y=CH3) showed the highest potency against c-Met kinase and the highest potency against PC-3 cell line. It is of great value to note that compounds 5g, 5h, 7c, 11c, 11d, and 11f showed higher potency than the reference foretinib. On the other hand, compounds 5b, 5d, 5e, 5f, 5g, 5h, 5i, 7b, 9b, 9c, 11c, 11d, 11f, 16d, and 16f revealed higher inhibition towards PC-3 cell line than the reference SGI-1776.

Inhibition of selected compounds against tyrosine kinases

The most potent compounds toward c-Met kinase 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 7b, 7c, 11c, 11d, and 11f were further investigated towards the five tyrosine kinases c-kit, FIT-3, VEGFR-2, EGFR, and PDGFRand the data were expressed through Table 2. It is clear that compounds 5d, 5e, 5f, 5g, 5h, 5i, 7c, 11c, 11d, and 11f showed the highest inhibitory effect while compounds 5b and 5c showed the least inhibition. It is clear that compounds 5e, 5h, 11d, and 11f exhibit the maximum inhibitory effect among the thirteen tested compounds. Specifically compound 5e (X=Y=Cl) showed the highest activity toward PDGFR kinase with IC50 0.27 nM, while compounds 5h (X=NO2, Y=Cl) and 11f (X=NO2, Y=OH) showed their highest inhibition towards c-Kit kinase with IC50’s 0.26 and 0.24 nM, respectively.

Table 2 Inhibition of tyrosine kinases (enzyme IC50 (nM) by compounds 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 7b, 7c, 11c, 11d, and 11f
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Cell proliferation assay

The anti-proliferative activities of the newly synthesized compounds were evaluated against five c-Met-dependent cancer cell lines (A549, HT-29, MKN-45, U87MG, and SMMC-7721) and one c-Met-independent cancer cell line (H460) using the standard MTT assay in vitro, with foretinib as the positive control (Tang et al. 2013, 2016; Zhou et al. 2014; Liao et al. 2014). The cancer cell lines were cultured in minimum essential medium (MEM) supplemented with 10% fetal bovine serum (FBS). Approximate 4 × 103 cells, suspended in MEM medium, were plated onto each well of a 96-well plate and incubated in 5% CO2 at 37 °C for 24 h. The compounds tested at the indicated final concentrations were added to the culture medium and the cell cultures were continued for 72 h. Fresh MTT was added to each well at a terminal concentration of 5 μg/mL, and incubated with cells at 37 °C for 4 h. The formazan crystals were dissolved in 100 mL of DMSO each well, and the absorbency at 492 nM (for absorbance of MTT formazan) and 630 nM (for the reference wavelength) was measured with an ELISA reader. All of the compounds were tested three times in each cell line. The results expressed as IC50 (inhibitory concentration 50%) were the averages of three determinations and calculated by using the Bacus Laboratories Incorporated Slide Scanner (Bliss) software.

Structure–activity relationship towards cancer cell lines

The structure activity relationship of the synthesized compounds against the cancer cell lines proceed in a similar manner like the activities towards c-Met kinase and PC-3 cell line. It is clear from Table 3 that compounds 5d, 5e, 5f, 7c, 9c, 11d, 11f, 16d, 16e, and 16f showed the highest potency among the synthesized molecules. Compounds 5e, 7c, 11d, and 11f showed inhibitory effect higher than the reference foretibit against the U87MG cell line. On the other hand, compounds 5h and 11f showed inhibition higher than foretinib against SMMC-7721 cell line with IC50’s 0.32, 0.38 nM, respectively. It is clear from Table 3 that the dihydrobenzo[b]thiophene derivatives showed moderate activities through the six cancer cell lines but relatively compound 3b (X=Cl) exhibited the highest activities. Through the arylhydrazono derivatives 5a–i, compounds 5d, 5e, 5f, 5g, and 5h exhibited the highest potencies. For the dihydrothieno[2′,3′:3,4]benzo[1,2-d]thiazole derivatives 7a–c and the thieno[2,3-f]chromene 9a–c, compounds 7c (X=NO2) and 9c (X=NO2) exhibited the highest potencies among the six compounds. For the thieno[2,3-f]chromene derivatives 11a–f, compounds 11d (X=Cl, Y=OH) and 11f (X=NO2, Y=OH) exhibited highest potencies. The thieno[2,3-e]indazol derivatives 13a–f showed moderate potencies but for the thiazol-2(3H)-ylidene)-4,5-dihydrobenzo[b]thiophene derivatives 16a–f, compounds 16d (X=Cl, Y=CH3), 16e (X=NO2, Y=OH), and 16f (X=NO2, Y=CH3) showed the highest potencies towards the six cancer cell lines.

Table 3 In vitro growth inhibitory effects IC50 ± SEM (μM) of the newly synthesized compounds towards cancer cell lines
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Inhibition of Pim-1 kinase by compounds 5e, 5f, 5h, 11d, and 11f

Although they are frequently implicated in acute myeloid leukemia (AML) (Fathi et al. 2012), PIM kinases are over expressed in many other types of hematological malignancies and solid tumors. Specifically, over expression has been identified in bladder (Guo et al. 2010), prostate (Wang et al. 2012), and head and neck cancers (Beier et al. 2007), chronic lymphocytic leukemia (Decker et al. 2014), multiple myeloma (Lu et al. 2013) and other B cell malignancies (Abad et al. 2011). Over expression of PIM kinases was often associated with poor prognosis in each of these cancers. For example, prostate tumors expressing high levels of PIM exhibited higher Gleason scores and differentiation (Cibull et al. 2006). Expression of Pim-1 has also been shown to predict poor prognosis in esophageal carcinoma (Liu et al. 2010) and gastric cancer (Eberz et al. 2009). This relation between the Pim-1 kinase and prostate cancer encouraged us to study the Pim-1 kinase of some compounds. Thus, the five compounds 5e, 5f, 5h, 11d, and 11f were selected for testing of their inhibition for the Pim-1 kinase (Table 4) due to their high activities toward c-Met kinase, PC-3 cell line, tyrosine kinases, and anti-proliferation activities toward the cancer cell lines. The study showed that compounds 5e (X=Y=Cl), 5h (X=NO2, Y=Cl), and 11f (X=NO2, Y=OH) showed IC50’s 0.72, 0.69, and 0.49 μM, respectively. While compounds 5f (X=Cl, Y=OCH3) and 11d (X=H, Y=OH) showed no activities.

Table 4 Inhibition of Pim-1 kinase for compounds 5e, 5f, 5h, 11d, and 11f
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Experimental

The solvents used through this work were dried prior to their use. All Melting points of the synthesized compounds were recorded on Buchi melting point apparatus D-545; IR spectra (KBr discs) were recorded on Bruker Vector 22 instrument. 13C NMR and 1H NMR spectra were recorded on Bruker DPX200 instrument in DMSO-d6 with tetramethylsilane as internal standard. Chemical shifts are mentioned in δ (ppm). Mass spectra were measured using EIMS (Shimadzu) and ESI-esquire 3000 Bruker Daltonics instrument. Elemental analyzes were carried out using the Microanalytical Data center at Cairo University. The completion of all reactions was monitored by thin layer chromatography on 2 × 5 cm pre-coated silica gel 60 F254 plates of thickness of 0.25 mm (Merck).

General procedure for the synthesis of the 2-amino-4,5-dihydrobenzo[b]thiophen-6(7H)-one derivatives 3a–c

To a solution of cyclohexan-1,4-dione (1.12 g, 0.01 mol) in 1,4-dioxane (40 mL) containing triethylamine (0.50 mL) each of elemental sulfur (0.32 g, 0.01 mol) and any of 2-cyano-N-phenylacetamide (1.60 g, 0.01 mol), N-(4-chlorophenyl)-2-cyanoacetamide (1.94 g, 0.01 mol) or N-(4-nitrophenyl)-2-cyanoacetamide (2.05 g, 0.01 mol) were added. The reaction mixture was heated under reflux for 2 h then poured onto ice/water containing few drops of hydrochloric acid. The formed solid product, in each case, was collected by filtration.

2-Amino-6-oxo-N-phenyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (3a)

Orange crystals (ethanol), yield 70% (2.00 g), m.p. 183–185 °C; (IR (KBr) ν max 3493, 3329, 3055, 2984, 1689, 1639, 1583; 1H NMR (DMSO-d6, 200 MHz): δ = 8.28 (s, 1H, D2O exchangeable, NH), 7.48–7.24 (m, 4H, C6 H4), 4.85 (s, 2H, D2O exchangeable, NH2), 2.79 (s, 2H, CH2), 1.92–1.65 (2t, 4H, 2CH2), 13C NMR (DMSO-d6, 75 MHz): δ = 166.2, 164.8 (2CO), 141.8, 140.2, 138.4, 133.5, 127.2, 124.8, 122.5, 120.5 (C6H5, thiophene C), 40.0, 38.8, 18.6 (3CH2); EIMS: m/z 286 [M]+ (26%); analysis calcd for C15H14N2O2S (286.35): C, 62.96; H, 4.93; N, 9.78; S, 11.20%. Found: C, 63.19; H, 4.69; N, 9.84; S, 11.36%.

2-Amino-N-(4-chlorophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (3b)

Orange crystals (ethanol), yield 76% (2.43 g), m.p. 210–213 °C; (IR (KBr) ν max 3479, 3351, 3055, 2986, 1688, 1639, 1590; 1H NMR (DMSO-d6, 200 MHz): δ = 8.26 (s, 1H, D2O exchangeable, NH), 7.48–7.24 (m, 4H, C6H4), 4.87 (s, 2H, D2O exchangeable, NH2), 2.81 (s, 2H, CH2), 1.90–1.63 (2t, 4H, 2CH2); 13C NMR (DMSO-d6, 75 MHz): δ =  166.0, 164.4 (2CO), 141.9, 140.7, 138.2, 133.6, 129.2, 125.3, 123.8, 121.2 (C6H5, thiophene C), 40.2, 38.8, 18.5 (3CH2); EIMS: m/z 320 [M]+ (28%); analysis calcd for C15H13ClN2O2S (320.79): C, 56.16; H, 4.08; N, 8,73; S, 10.00%. Found: C, 56.07; H, 4.17; N, 8.93; S, 10.25%.

2-Amino-N-(4-nitrophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (3c)

Pale yellow crystals (1,4-dioxane), yield 60% (1.98 g), mp 210–212 °C; IR (KBr) ν max 3480–3383, 3055, 2984, 1687, 1686, 1632, 1533; 1H NMR (DMSO-d6, 200 MHz): δ = 8.28 (s, 1H, D2O exchangeable, NH), 7.48–7.23 (m, 4H, Bz), 4.88 (s, 2H, D2O exchangeable, NH2), 3.73 (s, 2H, 2H-8), 2.94–2.20 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 164.8, 163.1 (CONH, C-6), 133.5, 132.6, 139.3, 129.0, 128.5, 124.9, 122.6, 121.8 (Bz, C-2, C-3, C-6a, C-7b), 34.8, 32.5, 20.7 (C-4, C-5, C-7); EIMS: m/z 331 [M]+ (35); analysis calcd for C15H13N3O4S (331.35): C, 54.37; H, 3.95; N, 12.68; S, 9.68%. Found: C, 54.42; H, 4.23; N, 12.70; S, 9.72%.

General procedure for the synthesis of the arylhydrazono derivatives 5a–i

To a cold solution of any of compounds 3a (2.86 g, 0.01 mol), 3b (3.20 g, 0.01 mol) or 3c (3.31 g, 0.01 mol) in ethanol (50 mL) containing sodium acetate (8.0 g) a solution of any of the diazonium salts (0.01 mol) [prepared by the addition of a solution of sodium nitrite (0.70 g, 0.01 mol) in water (10 mL) a cold solution of any of aniline (0.93 g, 0.01 mol), 4-chloroaniline (1.27 g, 0.01 mol) or 4-methoxyaniline (1.23 g, 0.01 mol) dissolved in concentrated hydrochloric acid (10 mL, 18 mol) with continuous stirring] was added with continuous stirring. The whole reaction mixture was left at room temperature for 2 h and the formed solid product was collected by filtration.

2-Amino-6-oxo-N-phenyl-7-(2-phenylhydrazono)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (5a)

Yellow crystals (ethanol), yield 75% (2.92 g), mp 210–213 °C; IR (KBr) ν max 3476–3343, 3055, 2988, 1689, 1686, 1631, 1535; 1H NMR (DMSO-d6, 200 MHz): δ = 8.32, 8.26 (2 s, 2H, D2O exchangeable, 2NH), 7.39–7.29 (m, 10H, 2Bz), 4.85 (s, 2H, D2O exchangeable, NH2), 2.96–2.24 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.6 (C-7), 164.6, 163.4 (CONH, C-6), 131.9, 130.4, 128.8, 126.6, 125.3, 124.6, 123.5, 123.0, 122.6, 121.6, 120.2, 119.4 (2Bz, C-2, C-3, C-6a, C-7b), 32.8, 20.6 (C-4, C-5); EIMS: m/z 390 [M]+ (16); analysis calcd for C21H18N4O2S (390.46): C, 64.60; H, 4.65; N, 14.35; S, 8.21%. Found: C, 64.83; H, 4.73; N, 14.59; S, 8.44%.

2-Amino-7-(2-(4-chlorophenyl)hydrazono)-6-oxo-N-phenyl-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxamide (5b)

Yellow crystals (ethanol), yield 80% (3.39 g), mp 166–169 °C; IR (KBr) ν max 3459–3327, 3055, 2988, 1686, 1686, 1631, 1532; 1H NMR (DMSO-d6, 200 MHz): δ = 8.30, 8.25 (2s, 2H, D2O exchangeable, 2NH), 7.46–7.25 (m, 9H, 2Bz), 4.82 (s, 2H, D2O exchangeable, NH2), 2.95–2.25 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.3 (C-7), 164.8, 163.2 (CONH, C-6), 132.1, 131.2, 128.5, 126.4, 125.2, 124.1, 122.9, 122.2, 120.6, 120.3, 119.8, 119.2 (2Bz, C-2, C-3, C-6a, C-7b), 32.7, 20.3 (C-4, C-5); EIMS: m/z 424 [M]+ (26); analysis calcd for C21H17ClN4O2S (424.90): C, 59.36; H, 4.03; N, 13.19; S, 7.55%. Found: C, 59.41; H, 3.88; N, 13.08; S, 7.80%.

2-Amino-7-(2-(4-methoxyphenyl)hydrazono)-6-oxo-N-phenyl-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxamide (5c)

Pale yellow crystals (ethanol), yield 64% (2.68 g), mp 204–207 °C; IR (KBr) ν max 3468–3331, 3056, 2989, 1686, 1686, 1633, 1532; 1H NMR (DMSO-d6, 200 MHz): δ = 8.32, 8.23 (2s, 2H, D2O exchangeable, 2NH), 7.49–7.26 (m, 9H, 2Bz), 4.80 (s, 2H, D2O exchangeable, NH2), 3.69 (s, 3H, OCH3), 2.93–2.27 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.1 (C-7), 164.5, 163.5 (CONH, C-6), 132.3, 131.8, 130.2, 128.6, 127.6, 127.2, 124.6, 123.2, 122.3, 122.8, 121.5, 120.4 (2Bz, C-2, C-3, C-6a, C-7b), 52.8 (OCH3), 32.2, 20.5 (C-4, C-5); EIMS: m/z 420 [M]+ (34); analysis calcd for C22H20N4O3S (420.48): C, 62.84; H, 4.79; N, 13.32; S, 7.63%. Found: C, 62.74; H, 4.88; N, 13.27; S, 7.82%.

2-Amino-N-(4-chlorophenyl)-6-oxo-7-(2-phenylhydrazono)-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxamide (5d)

Yellow crystals (ethanol), yield 58% (2.45 g), mp 180–182 °C; IR (KBr) ν max 3482–3341, 3054, 2986, 1689, 1687, 1634, 1536; 1H NMR (DMSO-d6, 200 MHz): δ = 8.34, 8.26 (2s, 2H, D2O exchangeable, 2NH), 7.44–7.22 (m, 9H, 2Bz), 4.80 (s, 2H, D2O exchangeable, NH2), 2.97–2.23 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.6 (C-7), 164.5, 163.3 (CONH, C-6), 132.6, 131.7, 128.3, 127.8, 126.1, 125.8, 124.6, 123.9, 122.4, 122.1, 120.3, 119.8 (2Bz, C-2, C-3, C-6a, C-7b), 32.9, 20.4 (C-4, C-5); EIMS: m/z 424 [M]+ (49); analysis calcd for C21H17ClN4O2S (424.90): C, 59.36; H, 4.03; N, 13.19; S, 7.55%. Found: C, 59.19; H, 4.22; N, 13.26; S, 7.69%.

2-Amino-N-(4-chlorophenyl)-7-(2-(4-chlorophenyl)hydrazono)-6-oxo-4,5,6,7-tetrahydro-benzo[b]thiophene-3-carboxamide (5e)

Orange crystals (ethanol), yield 74% (3.39 g), mp 235–238 °C; IR (KBr) ν max 3459–3362, 3056, 2986, 1687, 1686, 1634, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 8.36, 8.23 (2s, 2H, D2O exchangeable, 2NH), 7.52–7.23 (m, 8H, 2Bz), 4.83 (s, 2H, D2O exchangeable, NH2), 2.96–2.27 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.9 (C-7), 164.3, 163.6 (CONH, C-6), 133.8, 132.4, 129.6, 128.0, 127.4, 126.1, 123.8, 123.3, 122.6, 122.3, 121.7, 120.5 (2Bz, C-2, C-3, C-6a, C-7b), 32.6, 20.6 (C-4, C-5); EIMS: m/z 459 [M]+ (63); analysis calcd for C21H16Cl2N4O2S (459.35): C, 54.91; H, 3.51; N, 12.20; S, 6.98%. Found: C, 54.88; H, 3.80; N, 12.49; S, 7.29%.

2-Amino-N-(4-chlorophenyl)-7-(2-(4-methoxyphenyl)hydrazono)-6-oxo-4,5,6,7-tetra-hydrobenzo[b]thiophene-3-carboxamide (5f)

Orange crystals (1,4-dioxane), yield 80% (3.63 g), mp >300 °C; IR (KBr) ν max 3482–3341, 3055, 2988, 1689, 1687, 1636, 1526; 1H NMR (DMSO-d6, 200 MHz): δ = 8.38, 8.26 (2s, 2H, D2O exchangeable, 2NH), 7.49–7.21 (m, 8H, 2Bz), 4.85 (s, 2H, D2O exchangeable, NH2), 3.72 (s, 3H, OCH3), 2.94–2.25 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.5 (C-7), 164.4, 163.1 (CONH, C-6), 133.4, 132.7, 130.4, 129.6, 128.1, 127.6, 126.5, 124.6, 123.2, 122.5, 122.1, 121.3 (2Bz, C-2, C-3, C-6a, C-7b), 52.8 (OCH3), 32.4, 20.5 (C-4, C-5); EIMS: m/z 454 [M]+ (55); analysis calcd for C22H19ClN4O3S (454.93): C, 58.08; H, 4.21; N, 12.32; S, 7.05 %. Found: C, 57.82; H, 4.08; N, 12.42; S, 7.17%.

2-Amino-N-(4-nitrophenyl)-6-oxo-7-(2-phenylhydrazono)-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxamide (5g)

Red crystals (1,4-dioxane), yield 72% (3.13 g), mp 180–182 °C; IR (KBr) ν max 3469–3322, 3058, 2983, 1688, 1686, 1632, 1528; 1H NMR (DMSO-d6, 200 MHz): δ = 8.35, 8.23 (2s, 2H, D2O exchangeable, 2NH), 7.51–7.24 (m, 9H, 2Bz), 4.86 (s, 2H, D2O exchangeable, NH2), 2.96–2.23 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.3 (C-7), 164.6, 163.2 (CONH, C-6), 134.2, 133.2, 131.8, 130.3, 129.6, 127.4, 126.8, 125.2, 124.0, 123.8, 122.4, 120.6 (2Bz, C-2, C-3, C-6a, C-7b), 32.3, 20.6 (C-4, C-5); EIMS: m/z 435 [M]+ (42); analysis calcd for C21H17N5O4S (435.46): C, 57.92; H, 3.93; N, 16.08; S, 7.36%. Found: C, 58.04; H, 4.12; N, 15.89; S, 7.43%.

2-Amino-7-(2-(4-chlorophenyl)hydrazono)-N-(4-nitrophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (5h)

Red crystals (1,4-dioxane), yield 68% (3.19 g), mp 150–152 °C; IR (KBr) ν max 3473–3330, 3055, 2986, 1689, 1687, 1636, 1523; 1H NMR (DMSO-d6, 200 MHz): δ = 8.37, 8.26 (2 s, 2H, D2O exchangeable, 2NH), 7.47–7.26 (m, 8H, 2Bz), 4.85 (s, 2H, D2O exchangeable, NH2), 2.95–2.26 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.6 (C-7), 164.3, 163.6 (CONH, C-6), 133.8, 132.6, 131.4, 130.8, 129.4, 128.3, 126.5, 125.0, 124.3, 123.4, 122.6, 120.1 (2Bz, C-2, C-3, C-6a, C-7b), 32.6, 20.5 (C-4, C-5); EIMS: m/z 469 [M]+ (36); analysis calcd for C21H16ClN5O4S (469.90): C, 53.68; H, 3.43; N, 14.90; S, 6.82%. Found: C, 53.77; H, 3.36; N, 14.79; S, 7.05%.

2-Amino-7-(2-(4-methoxyphenyl)hydrazono)-N-(4-nitrophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (5i)

Pink crystals (1,4-dioxane), yield 72% (3.35 g), mp 266–269 °C; IR (KBr) ν max 3482–3339, 3056, 2985, 1684, 1688, 1634, 1536; 1H NMR (DMSO-d6, 200 MHz): δ = 8.34, 8.25 (2s, 2H, D2O exchangeable, 2NH), 7.49–7.24 (m, 8H, 2Bz), 4.87 (s, 2H, D2O exchangeable, NH2), 3.72 (s, 3H, OCH3), 2.98–2.24 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.4 (C-7), 164.8, 163.2 (CONH, C-6), 133.5, 132.3, 131.6, 130.3, 129.8, 127.9, 127.2, 125.6, 124.7, 123.8, 122.9, 119.6 (2Bz, C-2, C-3, C-6a, C-7b), 52.4 (OCH3), 32.4, 20.3 (C-4, C-5); EIMS: m/z 465 [M]+ (27); analysis calcd for C22H19N5O5S (465.48): C, 56.77; H, 4.11; N, 15.05; S, 6.89%. Found: C, 56.80; H, 4.28; N, 14.86; S, 7.13%.

General procedure for the synthesis of the thieno[2′,3′:3,4]benzo[1,2-d]thiazole derivatives 7a–c

To a cold solution of any of compounds 3a (2.86 g, 0.01 mol), 3b (3.20 g, 0.01 mol) or 3c (3.31 g, 0.01 mol) in 1,4-dioxane (40 mL) containing triethylamine (0.50 mL) each of elemental sulfur (0.32 g, 0.01 mol) and phenyl isothiocyanate (1.30 g, 0.01 mol) were added. The reaction mixture was heated under reflux for 2 h then poured onto ice/water containing few drops of hydrochloric acid and the formed solid product was collected by filtration.

7-Amino-N,3-diphenyl-2-thioxo-2,3,5,8b-tetrahydrothieno[2′,3′:3,4]benzo[1,2-d]thiazole-6-carboxamide (7a)

Yellow crystals (ethanol), yield 68% (2.95 g), mp 210–212 °C; IR (KBr) ν max 3459–3322, 3055, 2989, 1686, 1634, 1530, 1208; 1H NMR (DMSO-d6, 200 MHz): δ = 8.25 (s, 1H, D2O exchangeable, NH), 7.39–7.26 (m, 10H, 2Bz), 5.86 (s, 1H, H-8b), 6.01 (s, 1H, H-4), 4.83 (s, 2H, D2O exchangeable, NH2), 2.98 (s, 2H, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 178.2 (C-2), 163.5 (CONH, C-6), 106.6, 93.9 (C-3a, C-4), 138.2, 136.4, 133.4, 130.6, 129.6, 128.3, 126.0, 125.5, 124.5, 123.9, 122.6, 120.8 (2Bz, C-6, C-7, C-5a, C-8a), 34.5 (C-5); EIMS: m/z 435 [M]+ (39); analysis calcd for C22H17N3OS3 (435.58): C, 60.66; H, 3.93; N, 9.65; S, 22.08%. Found: C, 60.82; H, 4.18; N, 9.72; S, 22.93%.

7-Amino-N-(4-chlorophenyl)-3-phenyl-2-thioxo-2,3,5,8b-tetrahydrothieno-[2′,3′:3,4]-benzo[1,2-d]thiazole-6-carboxamide (7b)

Pale yellow crystals (ethanol), yield 58% (2.72 g), mp 203–205 °C; IR (KBr) ν max 3468–3328, 3056, 2984, 1687, 1632, 1532, 1205; 1H NMR (DMSO-d6, 200 MHz): δ = 8.25 (s, 1H, D2O exchangeable, NH), 7.43–7.23 (m, 9H, 2Bz), 5.84 (s, 1H, H-8b), 6.04 (s, 1H, H-4), 4.81 (s, 2H, D2O exchangeable, NH2), 2.94 (s, 2H, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 178.2 (C-2), 163.6 (CONH, C-6), 106.6, 93.9 (C-3a, C-4), 139.6, 137.2, 136.5, 134.6, 129.1, 128.8, 126.7, 125.3, 124.1, 123.7, 123.2, 120.8 (2Bz, C-6, C-7, C-5a, C-8a), 34.8 (C-5); EIMS: m/z 470 [M]+ (55); analysis calcd for C22H16ClN3OS3 (470.03): C, 56.22; H, 3.43; N, 8.94; S, 20.47%. Found: C, 65.27; H, 4.28; N, 8.83; S, 20.19%.

7-amino-N-(4-nitrophenyl)-3-phenyl-2-thioxo-2,3,5,8b-tetrahydrothieno[2′,3′:3,4]-benzo[1,2-d]thiazole-6-carboxamide (7c)

Orange crystals (1,4-dioxan), yield 69% (3.31 g), mp 177–179 °C; IR (KBr) ν max 3479–3380, 3058, 2989, 1688, 1636, 1531; 1H NMR (DMSO-d6, 200 MHz): δ = 8.27 (s, 1H, D2O exchangeable, NH), 7.46–7.21 (m, 9H, 2Bz), 5.85 (s, 1H, H-8b), 6.01 (s, 1H, H-4), 4.84 (s, 2H, D2O exchangeable, NH2), 2.96 (s, 2H, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 178.4 (C-2), 163.5 (CONH, C-6), 106.3, 93.8 (C-3a, C-4), 139.8, 137.6, 136.3, 134.4, 130.6, 129.3, 126.9, 126.1, 125.6, 123.4, 123.3, 120.6 (2Bz, C-6, C-7, C-5a, C-8a), 34.2 (C-5); EIMS: m/z 480 [M]+ (24); analysis calcd for C22H16N4O3S3 (480.58): C, 54.98; H, 3.36; N, 11.66; S, 20.02%. Found: C, 54.57; H, 3.50; N, 11.48; S, 20.29%.

General procedure for the synthesis of the 7-(ethoxymethylene)-4,5-dihydrobenzo[b]thiophen-6(7H)-onederivatives 9a–c

To a cold solution of any of compounds 3a (2.86 g, 0.01 mol), 3b (3.20 g, 0.01 mol) or 3c (3.31 g, 0.01 mol) in acetic acid (40 mL) ethyl orthoformate (0.76 g, 0.01 mol) was added. The reaction mixture was heated under reflux for 2 h then poured onto ice/water and the formed solid product was collected by filtration.

2-Amino-7-(ethoxymethylene)-6-oxo-N-phenyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (9a)

Yellow crystals (ethanol), yield 79% (2.70 g), mp 180–182 °C; IR (KBr) ν max 3467–3336, 3056, 2980, 1688, 1685, 1631, 1528; 1H NMR (DMSO-d6, 200 MHz): δ = 8.25 (s, 1H, D2O exchangeable, NH), 7.39–7.25 (m, 5H, Bz), 5.21 (s, 1H, C=CH), 4.83 (s, 2H, D2O exchangeable, NH2), 3.89 (q, 2H, OCH 2 CH3), 2.96–2.21 (2t, 4H, 2H-4, 2H-5), 1.15 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 165.1, 163.4 (CONH, C-6), 133.8, 132.4, 131.1, 125.3, 123.9, 122.8, 121.2, 120.4 (Bz, C-2, C-3, C-6a, C-7b), 103.8, 94.8 (C-7, C=CH), 56.3 (OCH 2 CH3), 32.5, 20.8 (C-4, C-5), 14.8 (OCH2 CH 3 ); EIMS: m/z 342 [M]+ (32); analysis calcd for C18H18N2O3S (342.41): C, 63.14; H, 5.30; N, 8.18; S, 9.36%. Found: C, 63.08; H, 5.62; N, 8.05; S, 9.52%.

2-Amino-N-(4-chlorophenyl)-7-(ethoxymethylene)-6-oxo-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxamide (9b)

Yellow crystals (ethanol), yield 70% (2.63 g), mp 201–204 °C; IR (KBr) ν max 3468–3329, 3055, 2989, 1689, 1686, 1632, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 8.25 (s, 1H, D2O exchangeable, NH), 7.39–7.25 (m, 4H, Bz), 5.21 (s, 1H, C=CH), 4.83 (s, 2H, D2O exchangeable, NH2), 3.89 (q, 2H, OCH 2 CH3), 2.96–2.21 (2t, 4H, 2H-4, 2H-5), 1.15 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 165.1, 163.4 (CONH, C-6), 133.8, 132.4, 131.1, 128.6, 125.3, 122.8, 121.2, 120.6 (Bz, C-2, C-3, C-6a, C-7b), 103.8, 94.8 (C-7, C=CH), 56.3 (OCH 2 CH3), 32.5, 20.8 (C-4, C-5), 14.8 (OCH2 CH 3 ); EIMS: m/z 376 [M]+ (48); analysis calcd for C18H17ClN2O3S (376.86): C, 57.37; H, 4.55; N, 7.43; S, 8.51%. Found: C, 57.41; H, 4.35; N, 7.62; S, 8.70%.

2-Amino-7-(ethoxymethylene)-N-(4-nitrophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxamide (9c)

Pale yellow crystals (1,4-dioxan), yield 60% (1.98 g), mp 210–212 °C; IR (KBr) ν max 3480–3383, 3055, 2984, 1687, 1686, 1632, 1533; 1H NMR (DMSO-d6, 200 MHz): δ = 8.24 (s, 1H, D2O exchangeable, NH), 7.49–7.21 (m, 4H, Bz), 5.25 (s, 1H, C=CH), 4.82 (s, 2H, D2O exchangeable, NH2), 3.86 (q, 2H, OCH 2 CH3), 2.95–2.20 (2t, 4H, 2H-4, 2H-5), 1.13 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 165.3, 163.2 (CONH, C-6), 133.7, 132.2, 130.8, 129.3, 125.3, 124.2, 123.9, 120.1 (Bz, C-2, C-3, C-6a, C-7b), 103.5, 94.7 (C-7, C=CH), 56.5 (OCH 2 CH3), 32.4, 20.6 (C-4, C-5), 14.8 (OCH2 CH 3 ); EIMS: m/z 387 [M]+ (26); analysis calcd for C18H17N3O5S (387.41): C, 55.80; H, 4.42; N, 10.85; S, 8.28%. Found: C, 55.68; H, 4.36; N, 11.03; S, 8.41%.

Synthesis of the thieno[2,3-f]chromene-8-carbonitrile derivatives 11a–f

To a solution of any of compounds 9a (3.42 g, 0.01 mol), 9b (3.76 g, 0.01 mol) and 9c (3.87 g, 0.01 mol) in 1,4-dioxan (40 mL) containing triethylamine (0.50 mL) either of malononitrile (0.66 g, 0.01 mol) or ethyl cyanoacetate (1.13 g, 0.01 mol) was added. The reaction mixture, in each case, was heated under reflux for 4 h then poured onto ice/water containing few drops of hydrochloric acid and the formed solid product was collected by filtration.

2,7-Diamino-8-cyano-9-ethoxy-N-phenyl-4H-thieno[2,3-f]chromene-3-carboxamide (11a)

Yellow crystals (1,4-dioxane), yield 55% (2.70 g), mp 245–247 °C; IR (KBr) ν max 3482–3341, 3054, 2982, 2221, 1689, 1633, 1525; 1H NMR (DMSO-d6, 200 MHz): δ = 8.27 (s, 1H, D2O exchangeable, NH), 7.37–7.28 (m, 5H, Bz), 5.04, 4.86 (s, 4H, D2O exchangeable, 2NH2), 5.80 (s, 1H, H-5), 3.86 (q, 2H, OCH 2 CH3), 3.06 (s, 2H, 2H-4), 1.13 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 163.8 (CONH), 142.6, 138.5, 133.1, 132.8, 132.0, 131.7, 128.6, 127.6, 125.2, 124.3, 123.9, 120.1 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 103.8, 94.8 (C-7, C=CH), 56.6 (OCH 2 CH3), 32.6 (C-4), 14.9 (OCH2 CH 3 ); EIMS: m/z 406 [M]+ (28); analysis calcd for C21H18N4O3S (406.46): C, 62.05; H, 4.46; N, 13.78; S, 7.89%. Found: C, 61.80; H, 4.66; N, 13.93; S, 8.05%.

2-Amino-8-cyano-9-ethoxy-7-hydroxy-N-phenyl-9,9a-dihydro-4H-thieno[2,3-f]chromene-3-carboxamide (11b)

Yellow crystals (1,4-dioxane), yield 62% (2.53 g), mp 165–168 °C; IR (KBr) ν max 3530–3326, 3055, 2980 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 2220, 1687, 1630, 1527; 1H NMR (DMSO-d6, 200 MHz): δ = 10.29 (s, 1H, D2O exchangeable, OH), 8.28 (s, 1H, D2O exchangeable, NH), 7.39–7.29 (m, 5H, Bz), 4.85 (s, 2H, D2O exchangeable, NH2), 5.83 (s, 1H, H-5), 3.85 (q, 2H, OCH 2 CH3), 3.08 (s, 2H, 2H-4), 1.14 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 163.6 (CONH), 142.2, 141.6, 138.2, 136.4, 134.1, 132.5, 129.8, 128.3, 127.3, 126.7, 123.5, 122.2, 121.3, 120.5 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 103.6, 94.6 (C-7, C=CH), 56.7 (OCH 2 CH3), 32.6 (C-4), 14.9 (OCH2 CH 3 ); EIMS: m/z 407 [M]+ (33); analysis calcd for C21H17N3O4S (407.44): C, 61.90; H, 4.21; N, 10.31; S, 7.87%. Found: C, 61.73; H, 4.32; N, 10.39; S, 7.92%.

2,7-Diamino-N-(4-chlorophenyl)-8-cyano-9-ethoxy-9,9a-dihydro-4H-thieno[2,3-f]chromene-3-carboxamide (11c)

Yellow crystals (1,4-dioxane), yield 72% (2.92 g), mp 177–179 °C; IR (KBr) ν max 3472–3353, 3055, 2980, 2220, 1687, 1633, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 8.29 (s, 1H, D2O exchangeable, NH), 7.45–7.25 (m, 4H, Bz), 5.18, 4.82 (s, 4H, D2O exchangeable, 2NH2), 5.80 (s, 1H, H-5), 3.87 (q, 2H, OCH 2 CH3), 3.13 (s, 2H, 2H-4), 1.14 (t, 3H, CH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 163.9 (CONH), 143.2, 142.8, 139.6, 137.2, 136.7, 134.2, 130.1, 128.8, 127.5, 125.6, 124.3, 123.7, 122.0, 120.8 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 103.4, 94.9 (C-7, C=CH), 56.8 (OCH 2 CH3), 32.6 (C-4), 14.5 (OCH2 CH 3 ); EIMS: m/z 440 [M]+ (20); analysis calcd for C21H17ClN4O3S (440.90): C, 57.21; H, 3.89; N, 12.71; S, 7.27%. Found: C, 57.49; H, 4.12; N, 12.92; S, 7.38%.

2-Amino-N-(4-chlorophenyl)-8-cyano-9-ethoxy-7-hydroxy-4H-thieno[2,3-f]chromene-3-carboxamide (11d)

Yellow crystals (1,4-dioxane), yield 78% (2.92 g), mp 177–179 °C; IR (KBr) ν max 3572–3353, 3055, 2980, 2223, 1687, 1633, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 9.85 (s, 1H, D2O exchangeable, OH), 8.29 (s, 1H, D2O exchangeable, NH), 7.49–7.24 (m, 4H, Bz), 4.83 (s, 2H, D2O exchangeable, NH2), 5.82 (s, 1H, H-5), 3.86 (q, 2H, OCH2 CH 3 ), 3.16 (s, 2H, 2H-4), 1.13 (t, 3H, OCH 2 CH3); 13C NMR (DMSO-d6, 75 MHz): δ = 163.9 (CONH), 143.2, 142.8, 139.6, 137.2, 136.7, 134.2, 130.1, 128.8, 127.5, 126.4, 124.5, 123.7, 122.0, 120.8 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 103.5, 94.9 (C-7, C=CH), 56.8 (OCH 2 CH3), 32.6 (C-4), 14.5 (OCH2 CH 3 ); EIMS: m/z 441 [M]+ (22); analysis calcd for C21H16ClN3O4S (441.89): C, 57.08; H, 3.65; N, 9.51; S, 7.26%. Found: C, 57.13; H, 3.85; N, 9.73; S, 7.42%.

2,7-Diamino-8-cyano-9-ethoxy-N-(4-nitrophenyl)-4H-thieno[2,3-f]chromene-3-carboxamide (11e)

Yellow crystals (1,4-dioxane), yield 71% (3.20 g), mp >300 °C; IR (KBr) ν max 3448–3339, 3055, 2980, 2221, 1688, 1631, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 8.27 (s, 1H, D2O exchangeable, NH), 7.49–7.21 (m, 4H, Bz), 5.19, 4.80 (s, 4H, D2O exchangeable, 2NH2), 5.83 (s, 1H, H-5), 3.84 (q, 2H, OCH 2 CH3), 3.15 (s, 2H, 2H-4), 1.12 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 163.5 (CONH), 143.6, 141.6, 140.2, 138.6, 136.7, 134.7, 132.3, 128.8, 127.9, 126.4, 124.8, 123.4, 122.0, 120.2 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 103.4, 94.5 (C-7, C=CH), 56.6 (OCH 2 CH3), 32.8 (C-4), 14.2 (OCH2 CH 3 ); EIMS: m/z 451 [M]+ (28); analysis calcd for C21H17N5O5S (451.46): C, 55.87; H, 3.80; N, 15.51; S, 7.10%. Found: C, 55.92; H, 3.93; N, 15.39; S, 7.22%.

2-Amino-8-cyano-9-ethoxy-7-hydroxy-N-(4-nitrophenyl)-4H-thieno[2,3-f]chromene-3-carboxamide (11f)

Orange crystals (1,4-dioxane), yield 62% (2.80 g), mp 205–208 °C; IR (KBr) ν max 3563–3319, 3057, 2980, 2220, 1688, 1636, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 9.84 (s, 1H, D2O exchangeable, OH), 8.26 (s, 1H, D2O exchangeable, NH), 7.52–7.20 (m, 4H, Bz), 4.85 (s, 2H, D2O exchangeable, NH2), 5.80 (s, 1H, H-5), 3.88 (q, 2H, OCH 2 CH3), 3.14 (s, 2H, 2H-4), 1.16 (t, 3H, OCH2 CH 3 ); 13C NMR (DMSO-d6, 75 MHz): δ = 163.3 (CONH), 143.5, 142.8, 140.4, 137.8, 136.7, 134.2, 130.5, 129.2, 127.6, 125.2, 123.3, 122.8, 121.8, 120.1 (Bz, C-2, C-3, C-7, C-8, C-9, C-6a, C-7b, C-9a), 103.8, 94.7 (C-7, C=CH), 56.4 (OCH 2 CH3), 32.4 (C-4), 14.8 (OCH2 CH 3 ); EIMS: m/z 452 [M]+ (28); analysis calcd for C21H16N4O6S (452.44): C, 55.75; H, 3.56; N, 12.38; S, 7.09%. Found: C, 55.91; H, 3.80; N, 12.46; S, 7.26%.

General procedure for the synthesis of the thieno[2,3-e]indazol derivatives 13a–f

To a solution of any of compounds 9a (3.42 g, 0.01 mol), 9b (3.76 g, 0.01 mol) and 9c (3.87 g, 0.01 mol) in ethanol (40 mL) either of hydrazine hydrate (0.50 g, 0.01 mol) or phenylhydrazine (1.08 g, 0.01 mol) was added. The reaction mixture, in each case, was heated under reflux for 3 h then poured onto ice/water containing few drops of hydrochloric acid and the formed solid product was collected by filtration.

2-Amino-N-phenyl-5,7-dihydro-4H-thieno[2,3-e]indazole-3-carboxamide (13a)

Yellow crystals (ethanol), yield 77% (2.83 g), mp 195–197 °C; IR (KBr) ν max 3492–3319, 3056, 2984, 1688, 1631, 1536; 1H NMR (DMSO-d6, 200 MHz): δ = 8.36, 8.22 (2 s, 2H, D2O exchangeable, 2NH), 7.37–7.27 (m, 5H, Bz), 6.18 (s, 1H, H-8), 4.87 (s, 2H, D2O exchangeable, NH2), 2.98–2.23 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.9 (C-5a), 163.6 (CONH), 143.8, 141.8, 136.2, 134.8, 129.6, 127.2, 125.8, 124.3, 122.5, 120.3 (Bz, C-2, C-3, C-8, C-3a, C-8a, C-8b), 32.6, 20.4 (C-4, C-5); EIMS: m/z 310 [M]+ (38); analysis calcd for C16H14N4OS (310.37): C, 61.92; H, 4.55; N, 18.05; S, 10.33%. Found: C, 62.18; H, 4.63; N, 17.79; S, 10.49%.

2-Amino-N,7-diphenyl-5,7-dihydro-4H-thieno[2,3-e]indazole-3-carboxamide (13b)

Yellow crystals (1,4-dioxane), yield 65% (2.50 g), mp 166–168 °C; IR (KBr) ν max 3474–3347, 3053, 2982, 1687, 1630, 1532; 1H NMR (DMSO-d6, 200 MHz): δ = 8.20 (s, 1H, D2O exchangeable, NH), 7.40–7.31 (m, 10H, 2Bz), 6.16 (s, 1H, H-8), 4.85 (s, 2H, D2O exchangeable, NH2), 2.97–2.21 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.5 (C-5a), 163.3 (CONH), 142.7, 142.2, 140.4, 136.8, 134.3, 132.7, 127.3, 124.1, 122.7, 119.2 (Bz, C-2, C-3, C-8, C-3a, C-8a, C-8b), 32.4, 20.3 (C-4, C-5); EIMS: m/z 386 [M]+ (22); analysis calcd for C22H18N4OS (386.47): C, 68.37; H, 4.69; N, 14.50; S, 8.30%. Found: C, 68.42; H, 4.39; N, 14.63; S, 8.49%.

2-Amino-N-(4-chlorophenyl)-5,7-dihydro-4H-thieno[2,3-e]indazole-3-carboxamide (13c)

Pale yellow crystals (1,4-dioxane), yield 69% (2.37 g), mp 211–213 °C; IR (KBr) ν max 3458–3329, 3056, 2980, 1685, 1633, 1531; 1H NMR (DMSO-d6, 200 MHz): δ = 8.37, 8.23 (2s, 2H, D2O exchangeable, 2NH), 7.48–7.24 (m, 4H, Bz), 6.15 (s, 1H, H-8), 4.86 (s, 2H, D2O exchangeable, NH2), 2.95–2.24 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.2 (C-5a), 163.5 (CONH), 144.3, 143.6, 140.3, 138.7, 137.2, 131.5, 127.3, 126.4, 123.4, 122.3 (Bz, C-2, C-3, C-8, C-3a, C-8a, C-8b), 32.6, 22.6 (C-4, C-5); EIMS: m/z 344 [M]+ (38); analysis calcd for C16H13ClN4OS (344.82): C, 55.73; H, 3.80; N, 16.25; S, 9.30%. Found: C, 55.90; H, 3.68; N, 16.33; S, 9.49%.

2-Amino-N-(4-chlorophenyl)-7-phenyl-5,7-dihydro-4H-thieno[2,3-e]indazole-3-carboxamide (13d)

Yellow crystals (1,4-dioxane), yield 77% (3.23 g), mp 201–204 °C; IR (KBr) ν max 3488–3327, 3055, 2982, 1688, 1630, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 8.25 (s, 1H, D2O exchangeable, NH), 7.44–7.25 (m, 9H, 2Bz), 6.19 (s, 1H, H-8), 4.87 (s, 2H, D2O exchangeable, NH2), 2.95–2.20 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.2 (C-5a), 163.5 (CONH), 142.4, 142.1, 139.2, 134.8, 133.1, 129.6, 128.2, 126.5, 124.2, 123.2, 122.3, 121.9, 120.2, 120.1 (Bz, C-2, C-3, C-8, C-3a, C-8a, C-8b), 32.3, 20.6 (C-4, C-5); EIMS: m/z 420 [M]+ (28); analysis calcd for C22H17ClN4OS (420.91): C, 62.78; H, 4.07; N, 13.31; S, 7.62%. Found: C, 62.91; H, 3.92; N, 13.40; S, 7.82%.

2-Amino-N-(4-nitrophenyl)-5,7-dihydro-4H-thieno[2,3-e]indazole-3-carboxamide (13e)

Pale yellow crystals (1,4-dioxane), yield 55% (1.95 g), mp 158–160 °C; IR (KBr) ν max 3473–3341, 3054, 2983, 1687, 1636, 1533; 1H NMR (DMSO-d6, 200 MHz): δ = 8.39, 8.26 (2 s, 2H, D2O exchangeable, 2NH), 7.52–7.28 (m, 4H, Bz), 6.18 (s, 1H, H-8), 4.83 (s, 2H, D2O exchangeable, NH2), 2.97–2.23 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.5 (C-5a), 163.6 (CONH), 144.6, 142.8, 140.2, 139.3, 137.6, 133.2, 128.1, 125.8, 124.6, 122.8 (Bz, C-2, C-3, C-8, C-3a, C-8a, C-8b), 32.4, 22.5 (C-4, C-5); EIMS: m/z 355 [M]+ (41); analysis calcd for C16H13N5O3S (355.37): C, 54.08; H, 3.69; N, 19.71; S, 9.02%. Found: C, 54.25; H, 3.52; N, 19.69; S, 9.32%.

2-Amino-N-(4-nitrophenyl)-7-phenyl-5,7-dihydro-4H-thieno[2,3-e]indazole-3-carboxamide (13f)

Pale yellow crystals (1,4-dioxane), yield 62% (2.67 g), mp 195–196 °C; IR (KBr) ν max 3480–3353, 3057, 2986, 1688, 1631, 1533; 1H NMR (DMSO-d6, 200 MHz): δ = 8.24 (s, 1H, D2O exchangeable, NH), 7.48–7.23 (m, 9H, Bz), 6.17 (s, 1H, H-8), 4.86 (s, 2H, D2O exchangeable, NH2), 2.95–2.26 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 172.3 (C-5a), 163.4 (CONH), 143.3, 142.1, 140.6, 138.2, 137.3, 137.1, 129.2, 126.3, 125.3, 124.2, 123.1, 122.1, 121.1, 120.9 (2Bz, C-2, C-3, C-8, C-3a, C-8a, C-8b), 32.6, 22.7 (C-4, C-5); EIMS: m/z 431 [M]+ (48); analysis calcd for C22H17N5O3S (431.47): C, 61.24; H, 3.97; N, 16.23; S, 7.43%. Found: C, 61.33; H, 3.72; N, 16.48; S, 7.52%.

General procedure for the synthesis of the thiazole derivatives 16a–f

To a solution of any of compounds 3a (2.86 g, 0.01 mol), 3b (3.20 g, 0.01 mol) or 3c (3.31 g, 0.01 mol) in dimethylformamide (40 mL) containing potassium hydroxide (0.56 g, 0.01 mol) phenylisothiocyanate (1.30 g, 0.01 mol) was added. The reaction mixture was stirred at room temperature for 24 h. On the next day, either of α-chloroacetate (1.22 g, 0.01 mol) or chloroacetone (0.92 g, 0.01 mol) was added. The whole reaction mixture was stirred at room temperature for another 24 h then poured onto ice/water containing hydrochloric acid (till pH 6) and the formed solid product was collected by filtration.

2-Amino-7-(4-hydroxy-3-phenylthiazol-2(3H)-ylidene)-6-oxo-N-phenyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (16a)

Orange crystals (acetic acid), yield 83% (3.82 g), mp 195–198 °C; IR (KBr) ν max 3552–3347, 3056, 2982, 1693, 1687, 1630, 1530; 1H NMR (DMSO-d6, 200 MHz): δ = 10.02 (s, 1H, OH), 8.26 (s, 1H, D2O exchangeable, NH), 7.39–7.27 (m, 10H, 2Bz), 6.08 (s, 1H, H-5′), 4.84 (s, 2H, D2O exchangeable, NH2), 2.97–2.22 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 165.8, 163.8 (C-6, CONH), 150.3, 144.8, 143.4, 141.9, 138.6, 136.3, 132.9 131.6, 130.8, 128.5, 127.3, 125.8, 121.9, 120.2 (2Bz, C-2, C-3, C-7, C-3a, C-7a, C-4′, C-5′), 106.9 (C-7), 32.8, 20.4 (C-4, C-5); EIMS: m/z 461 [M]+ (41); analysis calcd for C24H19N3O3S2 (461.56): C, 62.45; H, 4.15; N, 9.10; S, 13.89%. Found: C, 62.62; H, 4.39; N, 9.28; S, 13.93%.

2-Amino-7-(4-methyl-3-phenylthiazol-2(3H)-ylidene)-6-oxo-N-phenyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (16b)

Orange crystals (acetic acid), yield 68% (3.23 g), mp 158–160 °C; IR (KBr) ν max 3542–3347, 3054, 2980, 1690, 1688, 1632, 1531; 1H NMR (DMSO-d6, 200 MHz): δ = 8.28 (s, 1H, D2O exchangeable, NH), 7.42–7.25 (m, 10H, 2Bz), 6.05 (s, 1H, H-5′), 4.83 (s, 2H, D2O exchangeable, NH2), 6.70 (s, 3H, CH3), 2.98–2.21 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 165.6, 163.4 (C-6, CONH), 151.4, 145.6, 142.1, 140.2, 138.4, 137.0, 133.8, 132.1, 130.6, 129.9, 128.2, 127.1, 125.2, 120.3 (2Bz, C-2, C-3, C-7, C-3a, C-7a, C-4′, C-5′), 107.3 (C-7), 19.2 (CH3), 32.7, 20.6 (C-4, C-5); EIMS: m/z 459 [M]+ (32); analysis calcd for C25H21N3O2S2 (459.58): C, 65.33; H, 4.61; N, 9.14; S, 13.95%. Found: C, 65.52; H, 4.73; N, 9.26; S, 14.18%.

2-Amino-N-(4-chlorophenyl)-7-(4-hydroxy-3-phenylthiazol-2(3H)-ylidene)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (16c)

Orange crystals (acetic acid), yield 68% (3.23 g), mp 277–279 °C; IR (KBr) ν max 3531–3324, 3056, 2983, 1692, 1687, 1636, 1534; 1H NMR (DMSO-d6, 200 MHz): δ = 10.29 (s, 1H, D2O exchangeable, OH), 8.24 (s, 1H, D2O exchangeable, NH), 7.45–7.22 (m, 9H, 2Bz), 6.07 (s, 1H, H-5′), 4.85 (s, 2H, D2O exchangeable, NH2), 2.95–2.23 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 165.8, 163.2 (C-6, CONH), 150.6, 144.2, 142.8, 140.3, 138.4, 137.0, 133.8, 132.1, 130.6, 128.2, 125.2, 123.7, 122.9, 120.3 (2Bz, C-2, C-3, C-7, C-3a, C-7a, C-4′, C-5′), 106.8 (C-7), 32.9, 20.4 (C-4, C-5); EIMS: m/z 496 [M]+ (58); analysis calcd for C24H18ClN3O3S2 (496.00): C, 58.12; H, 3.66; N, 8.47; S, 12.93%. Found: C, 58.30; H, 3.80; N, 8.57; S, 13.18%.

2-Amino-N-(4-chlorophenyl)-7-(4-methyl-3-phenylthiazol-2(3H)-ylidene)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (16d)

Orange crystals (acetic acid), yield 71% (3.50 g), mp 159–162 °C; IR (KBr) ν max 3531–3313, 3056, 2982, 1692, 1688, 1632, 1531; 1H NMR (DMSO-d6, 200 MHz): δ = 8.25 (s, 1H, D2O exchangeable, NH), 7.46–7.21 (m, 9H, 2Bz), 6.06 (s, 1H, H-5′), 4.82 (s, 2H, D2O exchangeable, NH2), 2.73 (s, 3H, CH3), 2.95–2.24 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 165.8, 163.6 (C-6, CONH), 150.8, 147.2, 145.4, 140.6, 139.6, 136.3, 133.2, 132.8, 131.7, 129.3, 128.6, 127.6, 123.1, 119.8 (2Bz, C-2, C-3, C-7, C-3a, C-7a, C-4’, C-5’), 107.6 (C-7), 19.7 (CH3), 32.5, 20.3 (C-4, C-5); EIMS: m/z 494 [M]+ (44); analysis calcd for C25H20ClN3O2S2 (494.03): C, 60.78; H, 4.08; N, 8.51; S, 12.98%. Found: C, 60.62; H, 4.19; N, 8.70; S, 13.19%.

2-Amino-7-(4-hydroxy-3-phenylthiazol-2(3H)-ylidene)-N-(4-nitrophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (16e)

Orange crystals (acetic acid), yield 78% (3.94 g), mp 280–284 °C; IR (KBr) ν max 3526–3342, 3054, 2980, 1690, 1688, 1633, 1531; 1H NMR (DMSO-d6, 200 MHz): δ = 10.31 (s, 1H, D2O exchangeable, OH), 8.22 (s, 1H, D2O exchangeable, NH), 7.48–7.24 (m, 9H, 2Bz), 6.05 (s, 1H, H-5′), 4.83 (s, 2H, D2O exchangeable, NH2), 2.98–2.25 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 165.5, 163.6 (C-6, CONH), 151.3, 144.6, 142.3, 140.6, 139.1, 137.3, 135.7, 134.6, 132.8, 129.4, 127.6, 125.8, 123.4, 120.1 (2Bz, C-2, C-3, C-7, C-3a, C-7a, C-4′, C-5′), 106.5 (C-7), 32.4, 20.6 (C-4, C-5); EIMS: m/z 506 [M]+ (35); analysis calcd for C24H18N4O5S2 (506.55): C, 56.91; H, 3.58; N, 11.06; S, 12.66%. Found: C, 57.22; H, 3.63; N, 10.92; S, 12.80%.

2-Amino-7-(4-methyl-3-phenylthiazol-2(3H)-ylidene)-N-(4-nitrophenyl)-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (16f)

Orange crystals (acetic acid), yield 83% (4.18 g), mp 222–226 °C; IR (KBr) ν max 3438–3341, 3054, 2980, 1691, 1687, 1636, 1528; 1H NMR (DMSO-d6, 200 MHz): δ = 8.26 (s, 1H, D2O exchangeable, NH), 7.49–7.23 (m, 9H, 2Bz), 6.04 (s, 1H, H-5′), 4.83 (s, 2H, D2O exchangeable, NH2), 2.76 (s, 3H, CH3), 2.94–2.22 (2t, 4H, 2H-4, 2H-5); 13C NMR (DMSO-d6, 75 MHz): δ = 165.9, 163.6 (C-6, CONH), 151.3, 149.5, 146.3, 143.2, 1401, 138.1, 135.4, 133.1, 132.2, 130.1, 129.6, 127.2, 126.0, 120.2 (2Bz, C-2, C-3, C-7, C-3a, C-7a, C-4′, C-5′), 107.8 (C-7), 19.5 (CH3), 32.7, 20.5 (C-4, C-5); EIMS: m/z 504 [M]+ (28); analysis calcd for C25H20N4O4S2 (504.58): C, 59.51; H, 4.00; N, 11.10; S, 12.71%. Found: C, 59.49; H, 4.26; N, 10.82; S, 12.93%.

Conclusions

The main findings of these studies was the synthesis of new dihydrobenzo[b]thiophene derivatives. c-Met kinase investigations showed that compounds 5g, 5h, 7c, 11c, 11d, and 11f with higher potency than the reference foretinib. The anti-proliferative activities synthesized compounds were screened towards six cancer cell lines. On the other hand, compounds 5b, 5d, 5e, 5f, 5g, 5h, 5i, 7b, 9b, 9c, 11c, 11d, 11f, 16d, and 16f revealed higher inhibition towards PC-3 cell line. Compounds 5e, 5h, and 11f exhibit high inhibition towards Pim-1 kinase.