Simple and efficient synthesis of 4H-3,1-benzoxazines from 2-bromomethylphenyl isocyanate and amines

Abstract

Reaction of 2-bromomethylphenyl isocyanate (II; prepared by radical bromination of 2-tolyl isocyanate with N-bromsuccinimide) with aliphatic and aromatic amines takes place on the NCO group under formation of stable N-alkyl(aryl)-N'-(2-bromomethylphenyl)ureas III. On treatment with sodium hydrogen carbonate in water or sodium hydride in N,N-dimethylformamide, the ureas III are cyclized to give 2-alkyl(aryl)amino-4H-3,1-benzoxazines IV in good yields. Reaction of isocyanate II with alcohols leads to alkyl 2-bromomethylphenyl carbamates. Structure of the synthesized compounds has been proven by spectral methods and elemental analysis.