Pyrimidines. Part 53. Novel ring transformation induced by the substituent effect of the phenyl group. Reaction of 5-bromo-6-methyl-1-phenyluracil derivatives with amines and hydrazine to give hydantoins and pyrazolones

Abstract

Reaction of 5-bromo-6-methyluracil derivatives (1), possessing a phenyl or para-substituted phenyl group at the 1-position of the uracil ring, with methylamine and hydrazine hydrate causes novel ring transformations to give 1-arylhydantoins (2) and 4-ureidopyrazol-3-ones (9), respectively. The latter conversion into the pyrazolone (9) is a double ring transformation via a hydantoin intermediate (IV).