7-Alkylation and 7-sulphonylation of 5,6-dihydroimidazolo[2,1-b]thiazoles

Abstract

Reinvestigation of the alkylation of 3-phenyl-5,6-dihydroimidazolo[2,1-b]thiazole has shown that methylation occurs exclusively at the 7-position, and that the free base is readily solvolysed to a mixture of 1 -methylimidazolidin-2-one, 1 -methylimidazolidine-2-thione, and diphenacyl sulphide and disulphide. 3-Methyl-5,6-dihydroimidazolo[2,1-b]thiazole with methane- and arene-sulphonyl chlorides gave the corresponding 7-sulphonylthiazolium chlorides. On heating, these rearranged to 3-(2-chloroethyl)-4-methyl-3-aryl (or alkyl)sulphonylimido-2,3-dihydrothiazoles. The 7-(4-chlorophenylsulphonyl) derivative lost this substituent with aqueous base while concentrated aqueous ammonia attacked the 7a-position leading to a 3-[2-(p-chlorobenzenesulphonamido) ethyl]-2-imino-4-methyl-2,3-dihydrothiazole.