Methyl (Z)-2-[(benzyloxycarbonyl)amino]-3-dimethylaminopropenoate in the synthesis of heterocyclic systems. Synthesis of (benzyloxycarbonyl)amino substituted fused pyrimidinones

Methyl (Z)-2-[benzyloxycarbonyl)amino]-3-dimethylaminopropenoate (1) was us ed as a reagent for preparation of 3-[benzyloxycarbonyl)amino] substituted 4H-pyrido[1,2-a] pyrimidin-4-ones 17-21, 4H-pyrimido[1,2-b]pyridazin-4-ones 22 and 23, 5H-[1,2,4]triazolo[2,3-a]pyrimidin-5-one 24, 5H-thiazolo[3,2-a] pyrimidin-5-one 25, and 4H-pyrazino[1,2-a]pyrimidin-4-one 26. Removal of th e benzyloxycarbonyl group by catalytical transfer hydrogenation with Pd/C i n the presence of cyclohexene is selective to give 3-amino-4H-pyrido[1,2-a] pyrimidin-4-ones 27-30 in 85-92% yields, or with hydrogen bromide in acetic acid to give 3-amino-4H-pyrimido[1,2-b]pyridazin-4-one (31) and 6-amino-5H -thiazolo[3,2-a] pyrimidin-5-one (32) in 80% yields.