SYNTHESIS OF 6-STYRYLDIHYDROPYRIMIDINONES AND 6-STYRYLDIHYDROPYRIDINONES VIA THE RESPECTIVE 6-ALKYLPHOSPHONATES

Abstract

Trimethyl or triethyl phosphite in the Arbuzov reaction with 6-bromomethyl-3,4-dihydropyrimidin-2(1H)-one or analogous 6-bromomethyl-3,4-dihydropyridin-2(1H)-one provided the respective 6-alkylphosphonates in excellent yields. The heterocyclic alkylphosphonates are useful synthons in the Horner–Wadsworth–Emmons reaction for introducing a styryl moiety. Bromination of 6-methyl-4-phenyl-3,4-dihydropyridin-2(1H)-one with NBS in methanol resulted in an unexpected compound, while bromination in chloroform with bromine yielded the expected 6-bromomethyl-3,4-dihydropyridin-2(1H)-one, which undergoes facile nucleophilic substitutions. The intermediates and products are validated by single crystal X-ray diffraction.