Convenient Syntheses of 4‐Perfluoroalkyl‐6‐(α‐thienyl)‐2‐pyranones and Methyl 4‐(α‐Thienacyl)‐3‐perfluoroalkyl‐3‐butenoates.

Abstract In the presence of K 2 CO 3 , reaction of (α-thienacyl)methyltriphenyl phosphonium bromide ( 1 ) with methyl 2-perfluoroalkynoates ( 2 ) in CH 2 Cl 2 at room temperature gave methyl 4-(α-thienacyl)-2-triphenylphosphoranylidene-3-perfluoroalkyl-3-butenoates ( 3 ) in excellent yields. 4-Perfluoroalkyl-6-(α-thienyl)-6-pyranones ( 4 ) and methyl 4-(α-thienacyl)-3-perfluoroalkyl-3-butenoates ( 5 ) were obtained in high yield by hydrolysis of these methylene phosphoranes ( 3 ) with hot aqueous methanol. The butenoates ( 5 ) were isolated chromatographically as mixtures of Z and E isomers, the ratios of which were estimated by 1 H NMR. Reaction mechanisms are proposed to account for the formation of products 3, 4 and 5 .