Synthesis of ketene aminals with an imidazolidine ring by condensation of 4,5‐dihydro‐2‐(methylithio)‐1H‐imidazoles with active methylene compounds and some addition and cyclocondensation reactions

Abstract

AbstractThe 4,5‐dihydro‐2‐(methylthio)‐1H‐imidazoles 1a,b react with active methylene compounds 2a–f to afford the corresponding substituted methyleneimidazolidines 3a–f and 4c–f by elimination of methanethiol. The reaction of compounds 2g–j, which contain a more active carbonyl group, with 1a gives 3g–i by elimination of a methylthio group as well as an acyl group, too. 3a,g–i react with esters of α,β‐unsaturated acids to afford the corresponding imidazo[1,2‐a]pyridines 5,6, and 7 in an addition and cyclocondensation reaction sequence, but with diethyl azodicarboxylate only to give the addition product 8.