Transformation of 4-(1-dimethylaminoethylidene)-2-phenyl-5(4H) oxazolone into methyl 2-benzoylamino-3-oxobutanoate. The synthesis of 1-substituted 4- benzoylamino-3-methyl-5(2H)-pyra-zolones

Article abstract of DOI:10.1002/jhet.5570350607

Methyl 2-benzoylamino-3-oxobutanoate (3) was prepared from hippuric acid (1) which was converted with N,N-dimethylacetamide and phosphorus oxychloride into 4-(1-dimethylaminoethylidene)-2-phenyl-5(4H)-oxazolone (2) followed by hydrolysis with hydrochloric acid in methanol. Compound 3 was treated with hydrazines 4 to give 4-benzoylamino-3-methyl-1H-pyrazol-5(2H)-one (6a) and its 1-substituted derivatives 6b-j. The corresponding hydrazones 5f, i, j were isolated as intermediates.