Synthesis of optically active 1,4-benzoxazinones and 1,5-benzoxazepinones by regiocontrolled ring transformations of oxirane carboxylic acids and esters with aromatic o-hydroxyarylamines

Abstract

Enantiopure diethyl oxirane dicarboxylate 1 reacts with o-aminophenols 2 either to 1,4-benzoxazin-2-ones 5 or to the 1,5-benzoxazepin-2-one 4 while a condensed 1,4-oxazin-3-one 6 was obtained with 2-amino-3-hydroxypyridine. On the other hand optical active oxirane carboxylic acids 7 react with o-aminophenols 8 in the presence of DCC (dicyclohexylcarbodiimide) or isobutyl chloroformiate affording oxirane carboxamides 9 that can be ring transformed to either 2,3-dihydro-4 H-1,4-benzoxazin-3-ones 10 or 3-hydroxy-2,3-dihydro-5 H-1,5-benzoxazepin-4-ones 11 depending on the reaction conditions.