Efficient Synthesis of Dihydropyrimidine Hybrids via Guanidine-Based Biginelli Reaction

A versatile method has been developed for the synthesis of morpholine-dihydropyrimidine hybrids, 3-benzyl-6-methyl-5-(morpholine-4-carbonyl)-4-phenyl-3,4-dihydropyrimidin-2(1H)-one, through the construction of dihydropyrimidine (DHPM) via the guanidine-based Biginelli reaction followed by sodium tertiary butoxide mediated substitution of the benzyl group at the 3^rd position of DHPM ring. This substitution approach represents a novel method for obtaining N-substituted Biginelli products in good yields (72%–84%). Further, the ester group was subjected to intergroup conversion by morpholine using in situ generated diisobutyl(morpholino)aluminum. Notably, this reaction exhibited tolerance to various functional groups, resulting in the corresponding derivatives of dihydropyrimidine–morpholine hybrids in excellent yield (62%–82%).