New ring transformation reaction of imidazothiazole with acetylenic acid esters

Abstract

3-Phenyl-5,6-dihydroimidazo[2,1-b]thiazole (1) as a nucleophile reacted with acetylenic acid esters such as ethyl propiolate and dimethyl acetylenedicarboxylate to give the new ring transformation compounds (2-oxo-imidazoline-1-yl)acrylic acid ethyl esters (6a-b) and [2-oxo-imidazoline-1-yl]but-2-enedioic acid diethylesters (7a-b), respectively. Similarly, treatment of reactive imidazo[2,1-b]thiazolium betaines (3a-b) with acetylenic acid derivatives led to the corresponding ring transformation compounds. This reaction proceeded by the participation of water, and the resulting compounds were obtained in a mixture of cis and trans isomers.