1-Phenyl-5(6)-methyldihydrouracils and their transformations

Abstract

The reaction of aniline with methacrylic and crotonic acids gave N-phenyl-α- or β-methyl-β-alanines, which were converted to the corresponding 1-phenyl-5(6)-methyl- and 1-phenyl-2-thioxo-5(6)-methyldihydrouracils by the action of urea or thiocyanates in an acidic medium. The dihydrouracils were converted to ureido acids by the action of alkalis and to N-phenyl-β-alanine hydrazides by the action of hydrazine. 1-Phenyl-2-thioxo-5-methylhexahydropyrimidine was isolated in the reduction of the thioxodihydrouracil. The dihydro- and thioxodihydrouracils react with phosphorus pentasulfide to give 4-thioxo- and 2,4-dithioxodihydrouracils. 1-Phenyl-5(6)-methyldihydrocytosines were obtained from the 4-thioxodihydrouracils. The thioxodihydrouracils were subjected to bromination; 1-(4-bromophenyl)-5(6)-methyldihydrouracils were obtained from 1-phenyl-5(6)-methyldihydrouracils, and 1-phenyl-2-thioxo-5-bromo-5-methyldihydrouracil, which was converted to a uracil by dehydrobromination, was obtained from 1-phenyl-2-thioxo-5-methyldihydrouracil. 1-Phenyl-2-thioxo-5-methyluracil was also obtained by dehydrogenation of 1-phenyl-2-thioxo-5-methyldihydrouracil with sulfur.