Pyrimidines. XIV. Synthesis of 1‐substituted 5,6‐dihydrocytosines and an improved synthesis of 1‐substituted uracils

Abstract 1‐Substituted 5, 6‐dihydrouracils (VI) and 1‐substituted 5, 6‐dihydrocytosines (V) were prepared by cyclization of N‐substituted N‐β‐cyanoethyl ureas (IV) in acid and basic medium, respectively. Compounds N were synthesized from cyanic acid and β‐(substituted amino)propionitriles (III), the latter in turn were prepared from primary amines (I) and acrylonitrile (II). Preparations of 1‐substituted uracils (VII) from VI were carried out by known procedures.