Cycloaddition reactions of N-phenylsulfonyl-1-azabuta-1,3-dienes with mesoionic 2,4-diphenyl-1-methyl-1,3-oxazolium 5-oxide

Abstract

N-Phenylsulfonyl unsaturated imines (1) react with 2,4-diphenyl-3-methyl-1,3-oxazolium 5-oxide (2) giving 4-styrylimidazoles (3), open chain products (4) and pyrrol-3-ylcarboxaldehyde N-phenylsulfonylimines (5). The mechanism of formation of all the products as well as the different behaviour of imines 1 compared with those lacking the N-tosyl group are discussed. The structures have been assigned on the basis of ¹H NMR evidence and by X-ray analysis.