A new synthesis of flavones
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Iodine, in the presence of hot alcoholic sodium acetate, is shown to be a convenient reagent for the conversion of hydroxy flavanones into flavones. Naringenin, its 4′ and 4′: 7-dimethyl ethers, hesperetin and its dimethyl ether are thus oxidised smoothly into apigenin and its ethers and diosmetin respectively. The method is also suitable for glycosides; examples chosen are naringin, its monomethyl ether and hesperidin. The constitution of apiin is discussed and confirmed by correlation with that of naringin.
The method works smoothly in all cases where a free hydroxyl is present in the 5-position. In its absence a mixture is formed; by working in the cold the flavones can be obtained, whereas in the hot benzalcoumaranones could be isolated. In such cases the suitability of the phosphorus pentachloride method has been tested using 7-methoxy flavanone.
The reaction is considered to involve (1) iodination of the 3-position and (2) elimination of hydriodic acid and these are brought about smoothly with the help of the active and unstable acetate ions. If the second stage involves iodinated flavanone, flavone is obtained; on the other hand if the corresponding iodinated chalkone is present, benzal-coumaranone results.
KeywordsFlavone Apigenin Naringenin Flavanone Naringin
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- 2.Feuerstein and KostaneckiBer., 1898,31, 1757.Google Scholar
- 3.Kostanecki and TamborIbid.,, 1899,32, 2263. Cullinane and PhilpottJ.C.S., 1929, 1761. WheelerProc. Nat. Inst. Sci. (India), 1939,5, 267.Google Scholar
- 4.Mahal, Rai and VenkataramanJ.C.S., 1935, 866.Google Scholar
- 5.Kostanecki, Levi and TamborBer., 1899,32, 326.Google Scholar
- 6.Zemplen and BognarIbid.,, 1943,76, 452.Google Scholar
- 7.HattoriActa. Phyto. Chim., 1925,2, 99.Google Scholar
- 8.ButenandtAnn., 1928,464, 270. LaForge and SmithJ.A.C.S., 1930,52, 109.Google Scholar
- 9.Von GerichtenBer., 1900,33, 2908.Google Scholar
- 10.Perkin and HorsfallJ.C.S., 1900,77, 1315.Google Scholar
- 11.Rangaswami, Seshadri and VeeraraghaviahProc. Ind. Acad. Sci., A, 1939,9, 328. Narasimhachari and SeshadriIbid., Proc. Ind. Acad. Sci., A, 1948,27, 223.Google Scholar
- 12.PerkinJ.C.S., 1897,71, 805.Google Scholar
- 13.Chakravarti and GhoshJ.I.C.S., 1944, 171.Google Scholar
- 14.Czajnowski, Kostanecki and TamborBer., 1900,33, 1996.Google Scholar
- 15.Robinson and VenkataramanJ.C.S., 1926, 2344. Rao, Seshadri and ViswanadhamProc. Ind. Acad. Sci. A, 1949,29, 72.Google Scholar
- 17.Shinoda and SatoJ. Pharm. Soc. Japan, 1929,49, 71.Google Scholar
- 18.NakaokiIbid.,, 1938,58, 639.Google Scholar
- 19.Kostanecki, Lampe and TamborBer., 1904,37, 1402.Google Scholar
- 21.Freudenberg and KammulerAnn., 1927,451, 209.Google Scholar