STUDY OF LITHIUM ALUMINIUM HYDRIDE REDUCTION OF 5-ACETYL-1,6-DIMETHYL-4-PHENYL-3,4-DIHYDROPYRIMIDIN-2(1H)-ONE

In this paper, we investigated the LiAlH 4 -reduction of 5-acetyl-1,6-dimethyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (N-methylated Biginelli compound). Following the reduction and SiO 2 -promoted dehydration, (Z)-5-ethylidene-1-methyl-6-methylene-4-phenyltetrahydropyrimidin-2(1H)-one was isolated as the major product (33% yield). Chromatographic separation of the reaction products also allowed us to isolate (yield in parentheses) and fully spectrally characterize: 1,6-dimethyl-4-phenyl-5-vinyl-3,4-dihydropyrimidin-2(1H)-one (20%), 5-ethyl-1,6-dimethyl-4-phenyl-3,4-dihydro-pyrimidin-2(1H)-one (9%), 5-(1-hydroxyethyl)-1,6-dimethyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (5%). A possible mechanism explaining the formation of these products is proposed.