Pyrimidine derivatives and related compounds. 38. Synthesis of 1,3‐oxazine‐2,4‐diones and their reaction with nucleophiles. Ring transformation of 1,3‐oxazines to pyrimidines

Abstract

Abstract5,6‐Unsubstituted 1,3‐oxazine‐2,4‐diones (3) and 6‐unsubstituted 5‐methyl‐1,3‐oxazine‐2,4‐diones (4) were prepared by reduction of the corresponding 6‐chloro derivatives (1 and 2). Treatment of 6‐chloro‐3‐methyl‐1,3‐oxazine‐2,4‐dione (1a) with sodium azide, sodium cyanide, secondary amines and aniline gave the corresponding 6‐substituted compounds (7, 9, 10 and 11) while the reaction of 1a and 2a,b with primary aliphatic amines such as methylamine and ethylamine caused a ring transformation to pyrimidine ring system giving barbituric acids (13a‐d).