A Convenient Synthesis of Functionalized 1H-Pyrimidine-2-ones/thiones, Pyridazine and Imidazole; Experimental Data and PM3 Calculations

Abstract

The 4-(4-methoxybenzoyl)-5-(4-methoxyphenyl)-2,3-dihydro-2,3-furandione (1) and semicarbazones and thiosemicarbazones (2a-h) combine with loss of carbon dioxide and water yielding the 1 -methylenaminopyrimidin-2-one and thione derivatives (3a-h) in moderate yields (33-55%). Hyrolysis of 3a and 3e leads to the 1-aminopyrimidin-2-one/thione (4a, b), pyrimidine (6, 11), pyridazine (8, 13) and imidazole (10) derivatives were obtained from the reactions of 1 and Ethyl-4,5-dioxo-2-phenyl-4,5-dihydrofuran-3-carboxylate (12) with 1,5-diphenylcarbazide (5), 4-phenylsemicarbazide (7) and 1-phenylsemicarbazide (9). The electronic and geometric structures of reactants, transition states, intermediates and final products of the reaction of model reactants; 2,3-dihydro-1H-furan-2,3-dione and semicarbazone are calculated by the PM3 method. Transition states are further confirmed by vibrational analysis (computation of force constants analytically) and characterised by the corresponding imaginary vibration modes and frequencies.