Synthesis of 5,6-dihydroxy-2-phenyl-4-pyrimidinecarboxylic acid,methyl ester,a corrected structure

Pyrolysis of the adduct of benzamide oxime and dimethyl acetylenedicarboxylate leads to 5,6-dihydroxy-2-phenyl-4-pyrimidinecarboxylic acid methyl ester ( 4a ) rather than 4,5-dihydro-α,4-dioxo-2-phenyl-1H-imidazole-5-acetic acid, methyl ester ( 1 ).