Heterocyclic studies. Part XXXVII. Ready ring cleavage and decarbonylation of pyrimidine-5-carbaldehydes

Abstract

Treatment of 4-chloro-6-dialkylaminopyrimidine-5-carbaldehydes (4) with boiling water or dilute acetic or hydrochloric acid gave corresponding 3-dialkylamino-3-iminopropiononitriles (11) by ring cleavage and deformylation. The acid-catalysed deformylations, which followed ring cleavage, proceeded under extremely mild conditions and the formyl groups were lost as formic acid. Mechanisms for the ring cleavages and deformylations are proposed.4-Chloro-6-monoalkylaminopyrimidine-5-carbaldehydes (16; X = CHO) under the same conditions underwent mainly simple hydrolysis of the chloro-substituent to give 6-alkylamino-5-formylpyrimidin-4(3H)-ones (17; X = CHO). Some other 4,6-disubstituted pyrimidine-5-carbaldehydes underwent deformylation without ring cleavage.