Free-radical oxidation of 1,2,3,4-tetrahydro-2-oxopyrimidines

Abstract

Free-radical oxidation of 4-substituted 5-acetyl- and 5-carboethoxy-1,2,3,4-tetrahydro-2-oxopyrimidines using benzoyl peroxide under thermal conditions has been investigated to elucidate the effects of the nature of the substituents in the 4- and 5-positions on the rate of reaction. Whereas the presence of the acetyl group instead of the carboethoxy group in position 5 decreases the rate of oxidation, the nature of the additional substituent (electron-releasing or electron-withdrawing group) and also its location on the phenyl ring attached to C-4 of the tetrahydropyrimidinone ring effectively influence the rate of reaction. The latter observation supports the proposal that the removal of the 4-hydrogen on the heterocyclic ring occurs in the rate-determining step.