Addition of 4-Ethoxyimidazoles to Dimethyl Acetylenedicarboxylate and Transformation of the Adducts to Pyrimidin-5-yl Acetates

Four new 4-ethoxy-2-substituted imidazoles (1) were synthesized and high reactivity toward electrophiles was observed at the 5-position rather than the N atoms. For example, 1 reacted with dimethyl acetylenedicarboxylate to afford dimethyl (4-ethoxyimidazol-5-yl)fumarates (6) and-maleates (5). When 6 was treated with acid, a novel ring transformation occurred to give methyl (6-ethoxycarbonyl-3, 4-dihydro-4-oxopyrimidin-5-yl)acetates (12).