Cycloaddition of anhydro-3-hydroxy-2-phenylthiazolo[3,2-c]quinazolin-4-ium hydroxide with olefinic dipolarophiles

Abstract

Anhydro-3-hydroxy-2-phenylthiazolo[3,2-C]quinazolin-4-ium hydroxide (1) underwen; cycloaddition with ethyl acrylate and dimethyl tumarate to give pyrroloquinazoline derivatives [(3) and (7)] and COS, whereas with acetylenic dipolarophiles the anticipated ring-fused pyridinones e.g.(8) were obtained with extrusion of sulphur from the initial 1 : 1-cycloadduct; these represent the first rearrangements observed with olefinic dipolarophiles and mesoionic systems of this type.