Photochemical reactions of pyrimidinethiones with alkenes

Abstract

Photochemical addition reactions of pyrimidinethiones and related compounds with alkenes have been examined. Irradiation of pyrimidine-4(3H)-thiones (1a) in the presence of electron-poor alkenes gave the 4-mercaptoalkylated pyrimidines (5), whereas irradiation of (1a) in the presence of electron-rich alkenes gave 4-alkylthiopyrimidines (6). Irradiation of quinazoline-4(3H)-thiones (1c–e) and electron-poor alkenes gave 4-substituted quinazolines (9) and (10). This ready mode of carbon-carbon bond formation provides an efficient and novel method for alkylation of pyrimidine rings.