Photochemistry of 2,3,6-Trialkyl-4-pyrimidinones in Liquid Ammonia-Ether Solution. Chemistry of Dewar 4-Pyrimidinones

Article abstract of DOI:10.1021/jo00322a003

Irradiation of the 2,3,6-trialkyl-4-pyrimidinones 4 and 18 in liquid ammonia-ether (7:3) solution at -40 deg C gave the corresponding Dewar 4-pyrimidinones, 5 and 19, which decomposed in inert solvents at room temperature and did not revert to the corresponding 4-pyrimidinones.The first-order rate constants for disappearance of 5 and 19 were measured at 10-54 deg C.The solvolysis reactions of 5 and 19 occur in methanol to give the α-(aminoethylidene)-β-methoxy-β-lactams 6 and 20, respectively, whereas treatment of 5 and 19 in methanol containing sodium methoxide gave the imino ether 7 and the ketal 23, respectively.The reactions of 5 and 19 in methylamine-ether (1:4) solution afforded the imine derivatives 9 and 24, respectively.Furthermore, treatment of 5 in methanol-d containing sodium methoxide gave N-methyl-3-<(methoxyethylidene)amino>-2-butenamide-2-d (7D1) and N-methyl-3-<(methoxyethylidene)amino>-2-butenamide-2,4-d2 (7D2) as the major components.The imino ether 7 did not give the deuterated imino ether under similar conditions.The products (7, 9, 23, 24, and 27) formed in basic solutions are discussed in terms of abstraction of the methine proton by base from the Dewar 4-pyrimidinone or in terms of addition of nucleophile to the imino group of Dewar 4-pyrimidinone.