Preparation of 7-hydroxy derivatives of thionaphthene. New route for the synthesis of the thionaphthene system

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We have found that thieno[2, 3 -c ]pyry] ium sa l t s , which a r e r e a d i l y obtained by the acyla t ion of f i -ace tonyl th iophene [1,2] , undergo c leavage of the py ry l ium r ing under the ac t ion of a lka l i s , and the 3 ace tony l -2 acyl th iophenes so fo rmed then r e e y c l i z e with the fo rma t ion of 7-hydroxy de r iva t i ve s of thionaphthene: .sAc.o fiJ'J2 R 0 The r eac t i on is c a r r i e d out by heat ing aqueous ethanol ic solut ions of th ienopyry l ium sa l t s with an excess of caus t ic soda. In this way we have obtained 7 -hydroxy-5-methy l th ionaphthene (rap 68 ~ C) and 7 h y d r o x y 5 , 6 dimethyl thionaphthene (mp 99-100 ~ C), the s t r u c t u r e of which was shown by IR and NMR spec t roscopy . R E F E R E N C E S 1. G. N. Dorofeenko, L. V. Dulenko, V. I. Dulenko, and S. V. Krivun, ZhORKh, 1, 1171, 1965. 2. S. V. Krivun, L. V. Dulenko, V. I. Dulenko, and G. N. Dorofeenko, DAN, 166, 359, 1966. 26 August 1969 Donetsk Depa r tmen t of Phys i ca l and Organic Chemis t ry , Ins t i tu te of Phys ica l C h e m i s t r y AS UKrSSR