SYNTHESIS OF NEW PYRIDO[2,3-<i>d</i>]PYRIMIDIN-5-ONE, PYRIDO[2,3-<i>d</i>]PYRIMIDIN-7-ONE, AND PYRIMIDINO[4,5-<i>d</i>][1,3]OXAZINE DERIVATIVES FROM 5-ACETYL-4-AMINOPYRIMIDINES

Abstract

Methods were developed for the synthesis of new pyrido[2,3-d]pyrimidine and pyrimidino[4,5-d][1,3]oxazine derivatives. When heated under reflux with MeONa in BuOH, 5-acetyl-4-aminopyrimidines, acylated with carboxylic anhydrides or acid chlorides, are transformed into pyrido[2,3-d]pyrimidin-5-one derivatives, i.e., the acetyl methyl group and the amide carbonyl moiety are involved in the cyclization. In the presence of an activated CH₂ group (e.g., PhCH₂) in the amide moiety, the cyclization involves this group and the acetyl carbonyl giving rise to pyrido[2,3-d]pyrimidin-7-one derivatives. The reaction of 5-acetyl-4-aminopyrimidines with carboxylic acid chlorides under reflux in xylene followed by addition of a base affords pyrimidino[4,5-d][1,3]oxazines.