Abstract
Upon treatment of 2-phenyl-4, 5-dichloro-3 (2H)-pyridazinone (I) with sodium alkoxides, a ring contraction product, 1-phenyl-4-alkoxy-5-alkoxycarbonylpyrazole (III), was obtained as a major product. From the available data, a mechanism for the ring contraction was proposed. A most interesting finding is that formation of III does not involve an anomalous substitution as has been observed in the ring contraction of I to 1-phenyl-3-hydroxypyrazole-5-carboxylic acid (II) upon treatment with aqueous sodium hydroxide.
