Studies on Quinazolines. Part III. Synthesis of Some Fused-Ring Cationic and Mesoionic Derivatives of the 1,3-Thiazolo[3,2-c]quinazoline Ring System

Abstract

4-Allylthio-2-arylquinazolines 4a–c undergo cyclization by action of bromine to furnish 5-aryl-3-bromomethyl-2,3-dihydrothiazolo[3,2-c]quinazolin-4-ium bromide 5a–c. Compounds 5a–c undergo ring opening by action of water under acid catalysis to afford the corresponding dibromide derivatives 6a–c. Bromination of 3-allyl-2-aryl-4(3H)quinazolinethiones 7a–c leads to 5-aryl-2-bromomethyl-2,3-dihydrothiazolo[3,2-c]quinazolin-4-ium bromides 8a–c. However, 5-aryl-1,3-thiazolo[3,2-c]quinazolinium-3-olate 10a–c were prepared by the cyclodehydration of the corresponding thioglycolic acids 9a–c with Ac2O.