Fluorination

Living Edition
| Editors: Jinbo Hu, Teruo Umemoto

Functionalization of Alkynes for Preparing Alkenyl Fluorides

  • Shengzong Liang
  • Gerald B. HammondEmail author
  • Bo XuEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-981-10-1855-8_15-1

Introduction

Fluorine, called once a “small atom with a big ego,” has drawn much attentions from organic chemists due to its special properties [1, 2]. More specifically, nearly 25% of commercially pharmaceutical drugs and 40% of agrochemicals contain fluorine atoms [3, 4, 5]. Because quite few naturally occurring organofluoro compounds have been found, various strategies for introduction of fluorine into organic molecules have been developed since the last century [6, 7, 8, 9, 10, 11]. Among numerous fluorine-containing compounds, monofluoroalkene is of particular importance because alkene is ubiquitous in bioactive molecules [12, 13, 14, 15, 16, 17] and materials [18, 19, 20, 21]. Moreover, fluoroalkenes could also serve as fluorinated building blocks for further organic transformations [22, 23, 24, 25, 26]. Therefore, this entry will focus on the preparation of mono- or difunctionalized alkenyl fluorides from readily available alkyne precursors.

Hydrofluorination of Alkyne to Prepare Monofunctionalized Alkenyl Fluoride

Au-Mediated Hydrofluorination

In 2007, Sadighi’s group reported the first example of gold-catalyzed hydrofluorination of internal alkynes (Fig. 1) [27]. In the presence of NHC (N-heterocyclic carbenes)-gold catalyst and HF/Et3N as fluorinating reagent, both unsymmetrical and symmetrical internal alkynes 1 could be selectively transferred to mono-fluorinated alkenyl fluoride 2 in a trans-manner. Good regioselectivity was observed in the unsymmetrical cases.
Fig. 1

Gold-catalyzed hydrofluorination of internal alkynes

Two years later, Miller and coworkers utilized the similar strategy and designed a highly regioselective hydrofluorination of internal alkynes directed by carbonyl type of functional groups such as ester, carbamate, and imide (Fig. 2) [28]. In all cases, Z products were obtained as only or main products and fluorine was directed to the distal position. In terms of regioselectivity and stability, 2,2,2-trichloroethoxycarbonyl group was considered as the optimal directing group. Mechanistically, they proposed that the internal alkyne (use 3b as example) could complex with gold catalyst; then a six-membered intermediate 7 was formed. Finally, protodeauration of vinyl gold intermediate leads to the formation of product 4b, and the cationic gold species was regenerated (Fig. 3).
Fig. 2

Hydrofluorination of internal alkynes via directed NHC-gold catalysis

Fig. 3

Mechanism of hydrofluorination of internal alkynes via directed NHC-gold catalysis

More recently, a novel HF-based fluorinating reagent HF/DMPU was developed by the Hammond and Xu group. Compared with conventional HF-based reagents such as HF/pyridine and HF/Et3N, the stabilizer (DMPU) is much less basic, less nucleophilic, and less coordinating toward cationic metals. Therefore, it could be more suitably used in cationic metal- or acid-catalyzed reactions. Indeed, HF/DMPU was able to deliver fluorine to alkyne substrates 9 using an imidogold precatalyst (Fig. 4) [29]. Good functional group tolerance was observed, and both terminal and internal alkynes were suitable substrates for furnishing alkenyl fluorides 10.
Fig. 4

Hydrofluorination of alkynes with DMPU/HF

In 2015, a series of new NHC-gold bifluoride complexes were designed by Nolan and coworkers [30]. These gold complexes were very efficient catalysts for the transformation of alkynes 11 to alkenyl fluorides 12 (Fig. 5). A wide range of alkynes, including symmetrical and unsymmetrical internal alkynes, was examined under this catalysis. Fluorinated stilbene analogues and fluorovinyl thioethers were synthesized with good yields, stereo- and regioselectivity. Later, the same group reported that their NHC-gold bifluoride complex catalyzed the hydrofluorination of aryl iodoalkynes (Fig. 6) [31]. Different substituted (iodoethynyl)benzenes 13 were hydrofluorinated to give corresponding vicinal Z-fluoro-iodoalkenes 14 in good yields.
Fig. 5

NHC-gold bifluoride-catalyzed hydrofluorination of alkynes

Fig. 6

NHC-gold bifluoride-catalyzed hydrofluorination of aryl iodoalkynes

Ag-Mediated Hydrofluorination

In 2012, the Jiang group reported the hydrofluorination of electron-deficient alkynes such as aryl alkynyl esters and ketones (Fig. 7) [32]. Heterocyclic compound 15c was also a suitable substrate. AgF acts as both activator of the triple bond and also as a fluorine source. The hydrofluorinated products 16 were formed with high Z-selectivity. They also achieved the AgF-mediated fluorination of haloalkynes 18 (Fig. 8) [32]. Both electron-withdrawing and electron-donating groups on a phenyl ring were compatible with this protocol. Chlorinated and brominated alkynes were studied in this transformation. Aryl alkynyl esters and ketones could also be fluorinated to give 19 in high Z-selectivity.
Fig. 7

AgF-mediated hydrofluorination of alkynyl esters and ketones

Fig. 8

AgF-mediated hydrofluorination of haloalkynes

Shortly after Jiang’s work, Zhu and coworkers described a regio- and stereoselective trans-hydrofluorination of N-sulfonyl ynamides 20 using the same strategy (Fig. 9) [33]. A variety of functional groups were well tolerated. In contrast to Jiang’s work, the ynamide group was able to direct the installation of fluorine on the α-position of the triple bond in the ynamide. A possible mechanism was also proposed for this distinct α-selectivity (Fig. 10). Initially, the triple bond was activated by silver cation to form intermediate 22. Then nucleophilic attack of fluoride occurred on the more electron-deficient α-carbon, induced by the polarization of triple bond due to the electron-donation nature of nitrogen in ynamide. Finally, through protonolysis of intermediate 23 with water, the product 21 was generated.
Fig. 9

AgF-mediated hydrofluorination of N-sulfonyl ynamides

Fig. 10

Mechanism for α-selective hydrofluorination of N-sulfonyl ynamides

Cu-Mediated Hydrofluorination

Zhu and coworkers explored the (PPh3)3CuF-catalyzed hydrofluorination of ynamide (Fig. 11) [34]. In their experimental design, both oxazolidinones and pyrrolidinones bearing ynamides 24 were employed to give β-site-regioselective trans-fluoro enamide products 25 albeit no reaction for N-sulfonyl ynamides. It is worth mentioning that when a silver catalyst such as AgNTf2 was used, the N-sulfonyl ynamides could be smoothly converted to the corresponding fluoro enamide products with reversed α-selectivity, in contrast to the copper-catalyzed reaction.
Fig. 11

(PPh3)3CuF-catalyzed β-selective hydrofluorination of ynamides

The same group also found that when (PPh3)3CuF was replaced with a NHC-copper catalyst IPrCuF, α-site-regiocontrolled products 26 were observed, which provided a good complementary method for the aforementioned methodology (Fig. 12) [35]. This NHC-copper catalyst exhibited a better reactivity as demonstrated by the fact that the less reactive N-sulfonyl ynamides could be transferred to the desired α-fluoroenamides with high yield and selectivity.
Fig. 12

IPrCuF-catalyzed α-selective hydrofluorination of ynamides

The reason for the difference in site selectivity was explained (Fig. 13). Using ynamide 24a as example, an important five-membered ring intermediate 27 was formed; this intermediate is derived from the coordination of copper with the triple bond and the ynamide carbonyl oxygen, followed by subsequent nucleophilic addition of fluoride at β-position when (PPh3)3CuF is present. However, the larger steric hindrance of IPr ligands prohibits the metal center from coordinating with the ynamide carbonyl oxygen, thus leaving copper at the less crowded β-carbon and allowing fluoride to nucleophilically attack the α-carbon. Subsequent protonolysis of the corresponding intermediates 27 or 28 results in either α- or β-selective fluoroenamide 25a or 26a and the regenerated the copper catalyst.
Fig. 13

Mechanistic comparison for two Cu-mediated hydrofluorinations of ynamides

Metal-Free Hydrofluorination

In 2012, Thibaudeau and coworkers disclosed a metal-free hydrofluorination of ynamides using anhydrous HF as fluorine source at low temperature (Fig. 14) [36]. Interestingly, in this strategy, the HF was added onto the C-C triple bond in a cis-manner, thus leading to the formation of E enamide with high stereoselectivity. This unique stereoselectivity could be attributed to the steric hindrance in a key ketiminium intermediate between aromatic groups and incoming liquid anhydrous HF that forms a strong hydrogen-bonded long chain.
Fig. 14

Metal-free hydrofluorinations of ynamides

Fluorination of Alkyne to Prepare Difunctionalized Alkenyl Fluoride

Difunctionalization with C-C Bond Formation

In 2011, Liu and coworkers reported an efficient palladium-catalyzed tandem fluorination and cyclization of enynes 32 to synthesize fluorinated lactams using NFSI (N-fluorobenzenesulfonimide) as fluorine source (Fig. 15) [37]. The E isomer 33 was found to be the major product. A mechanism for this transformation was proposed to address the stereoselectivity (Fig. 16). A crucial cis-fluoropalladation on the triple bond occurred after a Pd-F species was generated in situ, which led to the formation of a vinyl fluoride intermediate 35. Then, through sequential alkene insertion into the vinyl-Pd bond, reduction with i-PrOH, and reductive elimination, the corresponding fluorinated lactam was formed with high E selectivity.
Fig. 15

Synthesis of fluorinated lactams through tandem fluorination and cyclization of enynes

Fig. 16

Mechanism for tandem fluorination and cyclization of enynes

In 2013 Yeh and coworkers accomplished the synthesis of fluorinated azabicycles via a carbofluorination of TBS (tert-butyldimethylsilyl)-protected nitrogen-containing cyclic enynols under metal-free condition (Fig. 17) [38]. Interestingly, the azabicyclic products were highly structurally dependent on the starting enynols. For instance, when the N-containing group was located at α-site of the siloxy group, the octahydroisoquinoline product 40 was generated. However, if this group was attached to β-site of the siloxy group, either carbospirocyclic or azaspirocyclic compounds 42 were formed instead.
Fig. 17

Synthesis of fluorinated azabicycles via a carbofluorination of TBS-protected nitrogen-containing cyclic enynols

Liu’s group successfully employed Selectfluor (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)) as fluorinating reagent and copper (0) as catalyst to synthesize fluorinated fluorenones from 1,6-enynes 43 (Fig. 18) [39]. A single electron transfer mechanism was proposed for this process, which rendered an unprecedented sequential C − C single bond cleavage and fluorination. It is noteworthy that the substituents on the aromatic ring that is adjacent to the C = C double bond had a strong effect on the products formed. For example, an electron-withdrawing group such as chlorine led to the formation of a mixture of t-Bu group-cleaved fluorinated product 44e and regular annulated product 45e with a ratio of 1:2.5, while the electron-donating methyl group gave only fluorinated product 44d. However, when the methyl group was installed at the ortho-position, a mixture of 44f and 45f was again observed.
Fig. 18

Cu(0)-mediated synthesis of fluorinated fluorenones from 1,6-enynes

The group of Weng developed a metal-free stereoselective synthesis of fluorinated pyrrolizidines 47 with Ph3CBF4 (triphenylcarbenium tetrafluoroborate) (Fig. 19) [40]. The formation of tertiary carbocation derived from tertiary allylic alcohol and nucleophilic attack from BF4 anion allowed for the tandem fluorination and annulation to occur. In addition, the special diastereoselectivity observed was induced by fluoride anti-addition of allylic carbonium ion from the less hindered β-face.
Fig. 19

Stereoselective synthesis of fluorinated pyrrolizidines with Ph3CBF4

In 2016, Zhang and coworkers reported a silver-mediated ring expansion and fluorination of ethynyl

cyclobutanols (Fig. 20) [41]. The very mild reaction conditions in this transformation provided the 2-methylenecyclopentanones 49 in moderate to good yields. A radical-facilitated mechanism was suggested (Fig. 21). This reaction was initiated by coordination of the silver catalyst with a cyclobutanol, the resulting intermediate 50 was then oxidized by Selectfluor and, following homolysis, the alkyl radical 52, together with a silver (II) fluoride species, was generated. Finally, a 5-exo-dig cyclization and reductive elimination of Ag(III) led to formation of the cyclopentanone 49, and Ag(I) was regenerated for the next catalytic cycle.
Fig. 20

Silver-mediated ring expansion and fluorination of ethynyl cyclobutanols

Fig. 21

Mechanism for silver-mediated ring expansion and fluorination of ethynyl cyclobutanols

A methodology for the fast transformation of alkynols to cyclic alkenyl fluorides was developed by Alonso and coworkers in 2014 (Fig. 22) [42]. Tetrafluoroboric acid was used in this process, serving as both fluoride and proton sources. Both tertiary and secondary alcohols were suitable substrates. This cyclization reaction was triggered by the formation of carbocation intermediate. Ji and coworkers applied a similar strategy on the intermolecular coupling between alcohol and alkyne to synthesize monofluoroalkene 58 (Fig. 23) [43]. However, this method suffers from the formation of a mixture of E, Z isomers and low yields.
Fig. 22

Synthesis of cyclic alkenyl fluorides through carbocyclization

Fig. 23

Synthesis of monofluoroalkene via intermolecular coupling between alcohol and alkyne

Difunctionalization with C-N Bond Formation

In 2012, Liu’s group reported a highly efficient silver-catalyzed aminofluorination of alkynes with NFSI as electrophilic fluorine source (Fig. 24) [44]. Through this strategy, both fluorinated heterocyclic compounds fluoroisoquinolines 60 and fluoropyrrolo[α]isoquinolines 62 could be accessed. And it should be mentioned that when TFBY (ethyl 4,4,4-trifluorobutynate) rather than DMAD was subjected to the optimized conditions, both fluorine and trifluoromethyl groups could be introduced into pyrrolo[α]isoquinolines simultaneously.
Fig. 24

Silver-catalyzed aminofluorination of alkynes

Xu and coworkers disclosed a gold-catalyzed intramolecular aminofluorination of alkynes for the synthesis of fluorinated pyrazoles 64 under mild conditions (Fig. 25) [45]. A wide range of substrate scope and high yields were achieved with this method, although a competing nonfluorinated pyrazole 65 was also formed through protodeauration of the alkenyl gold species with proton.
Fig. 25

Gold-catalyzed aminofluorination of alkynes

Michelet and coworkers described, in 2013 and 2014, a two-step, one-pot synthesis of fluoroindoles from o-alkynylanilines 66 (Fig. 26) [46, 47]. Initially, the gold catalyst coordinated with alkynylaniline 66, and, following the nucleophilic addition of nitrogen to the activated triple bond, it afforded a trans-alkenyl gold intermediate 69. Then, the gold (I) species was oxidized by Selectfluor to generate a gold (III) complex 70. Finally, through reductive elimination, the gold catalyst was regenerated and the monofluoroindole was generated (Fig. 27).
Fig. 26

Gold-mediated one-pot synthesis of fluoroindoles from o-alkynylanilines

Fig. 27

Mechanism of gold-mediated one-pot synthesis of fluoroindoles

Difunctionalization with C-O Bond Formation

In 2008, Gouverneur’s group studied the gold-catalyzed alkoxyhalogenation of β-hydroxy-α,α-difluoroynones, in which the use of Selectfluor as electrophilic fluorinating reagent furnished the trifluorinated dihydropyranones 72 (Fig. 28) [48]. However, this protocol suffered from low yields due to the fact that the competing alkoxyhydrogenated products 73 formed through protodeauration were more dominant than the alkoxyfluorinated products 72 formed through fluorodeauration.
Fig. 28

Gold-catalyzed alkoxyfluorination of β-hydroxy-α,α-difluoroynones

Hammond and Xu developed a gold-catalyzed tandem cycloisomerization and monofluorination of alkynylic alcohols 74 to synthesize fluorinated lactones 75 (Fig. 29) [49]. The authors screened different gold catalysts, and the best yield and selectivity of the desired fluorinated lactone was achieved using tri-o-tolylphosphine gold, albeit only two examples were reported. Later, Ryu and coworkers reported that in the presence of Selectfluor, the O-methyl oximes 77 could be converted to 4-fluoroisoxazoles 78 through a cascade cyclization and fluorination process (Fig. 30) [50]. Interestingly, this strategy, compared with Gouverneur’s work, to a great extent, avoided the formation of undesired nonfluorinated product; thus much higher yields of desired fluorinated products were obtained. This could be attributed to the use of excess amount of base NaHCO3.
Fig. 29

Gold-catalyzed tandem cycloisomerization and monofluorination of alkynylic alcohols

Fig. 30

Gold-catalyzed tandem cyclization-fluorination of O-methyl oximes

Difunctionalization with C-Cl, C-Br, and C-I Bond Formation

In 1995, Dolenc and coworkers reported a methodology for the chlorofluorination of alkynes by the combination of N-chlorosaccharin and HF/pyridine (Fig. 31) [51]. A similar strategy was utilized by Dear for the bromofluorination of alkynes, in which N-bromoacetamide and anhydrous HF functioned as bromine and fluorine sources, respectively (Fig. 32) [52]. Shellhamer and coworkers found that iodine monofluoride (IF) could be generated from XeF2 and I2, thus giving access to fluoroiodohexene 84 under mild conditions (Fig. 33) [53]. A more general approach for halofluorination of alkynes was achieved by Olah’s group (Fig. 34) [54]. In their remarkable method, the combination of Olah’s reagent and N-halosuccinimide worked efficiently to install both fluorine and another halogen at the same time.
Fig. 31

Chlorofluorination of alkynes with N-chlorosaccharin and HF/pyridine

Fig. 32

Bromofluorination of alkynes with N-bromoacetamide and anhydrous HF

Fig. 33

Iodofluorination of alkynes with XeF2 and I2

Fig. 34

Halofluorination of alkynes with combination of Olah’s reagent and N-halosuccinimide

More recently, new strategies have been developed for halofluorination reactions. For example, in 2012, Jiang and coworkers found that terminal alkynes could be easily bromofluorinated using NBS (N-bromosuccinimide) and AgF with good regio- and stereoselectivity (Fig. 35) [55]. A wide range of terminal alkynes bearing either electron-withdrawing or electron-donating functional groups could be converted to Z bromofluorinated alkenes 88 exclusively and in high yields. The formation of a bromoalkyne mediated by silver was essential for the following trans-addition of AgF and protonolysis of the alkenyl silver intermediate.
Fig. 35

Bromofluorination of terminal alkynes with NBS and AgF

Tingoli and coworkers reported a method for the iodofluorination of alkynes using 4-iodotoluene difluoride as the nucleophilic fluorine source. However, the reversed addition pattern of iodine and fluorine was observed, leading to the formation of E iodofluoroalkenes 90 (Fig. 36) [56]. Internal alkynes provided good yields and selectivity, whereas the terminal iodofluoroalkene was obtained in very poor yield (16%).
Fig. 36

Iodofluorination of alkynes with p-tolIF2 and I2

In order to achieve better substrate tolerance for the iodofluorination of alkynes, Hara and Ukigai successfully applied the combination IF5-pyridine-HF for this transformation (Fig. 37) [57]. In this creative strategy, the IF5-pyridine-HF reagent was reduced in situ with a reductant hydroquinone to form a highly reactive “IF” species accompanying by the release of HF and p-quinone. Then the “IF” species underwent anti-addition toward alkynes to furnish the trans-iodofluoroalkene 92. Both internal and terminal alkynes worked equally well with this method, and a variety of functionalities such as ester, ketone, as well as sulfane were tolerated.
Fig. 37

Iodofluorination of alkynes with IF5-py-HF reagent

Bromonium or iodonium salts are very useful reagents due to their good performance as leaving groups. Several different strategies have been explored. For instance, in 2004, Yoshida and coworkers described that upon treatment with HBF4, the 4-iodotoluene difluoride could smoothly deliver both fluorine and iodine onto alkyne substrates to afford fluoroalkenyliodonium tetrafluoroborate 94 (Fig. 38) [58]. Fluoroalkenylbromonium tetrafluoroborate 96 could also be synthesized under a similar procedure (Fig. 39) [59]. Ochiai and coworkers found that in the presence of BF3 and difluoro(aryl)-λ3-bromane, the terminal alkynes 95 were efficiently transferred to β-fluoroalkenyl-λ3-bromanes 96 with good yields and selectivity. A tetracoordinated λ3-bromane 97 was considered as key intermediate in this process. Then after releasing of BF4 , bromonium 98 was generated and was attacked by nucleophilic fluoride to give product 96.
Fig. 38

Synthesis of fluoroalkenyliodonium salts with p-tolIF2

Fig. 39

Synthesis of β-fluoroalkenyl-λ3-bromanes

Difunctionalization with C-S and C-Se Bond Formation

Montevecchi and coworkers reported, in 1990, a one-pot procedure for the synthesis of β-fluoroalkenyl sulfides 100 (Fig. 40) [60]. The reactivity and selectivity greatly depended on the substituents on the alkyne. 4-Octyne provided a high yield (77%) of the product and with almost exclusive E selectivity (E/Z = 99/1), but a poor yield (33%) and reversed Z-selectivity (E/Z = 8/92) was observed in the case of phenylacetylene. Mechanistically, a thiirenium ring 101, generated from the reaction between alkynes and NBSA promoted by Lewis acid BF3, was postulated as intermediate; then under nucleophilic attack of fluoride generated from fluoroborate, the β-fluoroalkenyl sulfide was formed in a trans-manner. It is should be noted that the by-products bis(phenylthio)alkene and diphenyldisulfane were also observed.
Fig. 40

Synthesis of β-fluoroalkenyl sulfides with NBSA and ATBF

More recently, a very reactive arylbis(arylsulfanyl) sulfonium tetrafluoroborate ArS(ArSSAr)+BF4 was successfully introduced for the thiofluorination of alkynes by the Yoshida group (Fig. 41) [61]. The symmetrically alkyne 102a could be converted to the corresponding E thiofluoro alkene 103a in good yield and stereoselectivity. Yet, the unsymmetrical alkyne 102b provided a pair of regioisomers in nearly equal amounts. The introduction of a directing group such as the ethoxy group could tune regioselectivity to afford a single isomer. The C-Se bond could also be constructed in similar way. For instance, in 1990, Anker and coworkers reported a phenylselenofluoration of alkynes using both NPSP (N-(phenylseleno)phthalimide) and Et3N·3HF (Fig. 42) [62]. Single stereoselective E products 105 were formed, while both symmetrical and unsymmetrical internal alkynes were subjected albeit a non-separable regioisomer obtained in unsymmetrical cases.
Fig. 41

Thiofluorination of alkynes using ArS(ArSSAr)+BF4

Fig. 42

Phenylselenofluoration of alkyne with NPSP and Et3N·3HF

Two years later, the Tomoda group reported a new method for fluoroselenylation of alkynes (Fig. 43) [63]. A highly active benzeneselenenyl fluoride equivalent was generated through the reaction of AgF and benzeneselenenyl bromide via short-time ultrasound irradiation. The in situ formed “PhSeF” then engaged in an electrophilic addition to an alkyne to provide the 2-fluoro-1-alkenyl phenyl selenide 107 in moderate yield. Similar to Anker’s work, the unsymmetrical internal alkyne led to the formation of two regioisomers.
Fig. 43

Phenylselenofluoration of alkyne with AgF and PhSeBr

Diphenyl diselenide was also found to be a good phenylselenyl source for fluoroselenylation of alkynes upon oxidation with electrophilic fluorine reagents. In 2004, Tingoli and coworkers described that the oxidation of diphenyl diselenide with DFIT (4-iodotoluene difluoride) was able to generate in situ a phenylselenofluorinating reagent, thus allowing the addition of phenylselenenyl group and fluorine onto alkynes to give corresponding products 109 with E selectivity (Fig. 44) [64].
Fig. 44

Phenylselenofluoration of alkyne with diphenyl diselenide and DFIT

Poleschner and coworkers reported a similar fluoroselenylation of alkynes, but, in contrast to Tingoli’s work, they used a different fluorine-based oxidant XeF2 (Fig. 45) [65]. Mechanistically, a phenylselenirenium ion was believed responsible for the E-configuration of the products. In addition, alkylselenofluoration of alkynes was achieved as well by using the corresponding dialkyl diselenides. Moreover, these researchers found that the phenylseleno(trialkyl)silanes exhibited higher reactivity compared with diselenides toward this selenofluoration reaction.
Fig. 45

Phenylselenofluoration of alkyne with diphenyl diselenide and XeF2

Conclusion and Future Directions

In this entry, various strategies were summarized toward the preparation of mono- and difunctionalized alkenyl fluorides from alkynes. The advent of this intriguing field will benefit many areas. On the one hand, the introduction of fluorine atom onto alkynes may bring significant changes in pharmaceutical agrochemical or material sciences. On the other hand, it will provide valuable organic building blocks such as halofluoroalkenes for further transformations. We expect more novel fluorinating reagents and methodologies to prepare mono- and difunctionalized alkenyl fluorides will be developed.

Cross-References

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© Springer Nature Singapore Pte Ltd. 2018

Authors and Affiliations

  1. 1.Department of ChemistryUniversity of LouisvilleLouisvilleUSA
  2. 2.College of Chemistry, Chemical Engineering and BiotechnologyDonghua UniversityShanghaiChina