Thio- and seleno-lactonizations of alkynoic acids

Abstract

Regio- and stereo-specific thio- and seleno-lactonizations of hept-4-ynoic acid (1a), hex-4-ynoic acid (1b), and pent-4-ynoic acid (1c) can be achieved by treatment of benzenesulphenyl chloride and benzeneselenenyl chloride using a hydrogen chloride capture such as triethylamine or a better capture in most cases, 3,4-dihydro-2H-pyrido[1,2a]pyrimidin-2-one. N-Phenylselenophthalimide is also effective for the selenolactonization, although E and Z lactones (E)-(2c; X = Se) and (Z)-(2c; X = Se) are formed from (1c). Cleavage reactions of γ-alkylidene-γ-butyrolactones afford a new preparative method for 4-oxoalkanoic acid derivatives.