A Novel Synthesis of 4H-1, 4-Benzoxazines

Abstract

The reaction of methyl 2-chloro-5-ethoxycarbonylamino-4-fluorobenzoate (4a) and 1-bromo-3, 3-dimethyl-2-butanone (2) in the presence of 2.2 eq of lithium bis(trimethylsilyl)amide afforded the 4H-1, 4-benzoxazine (6a) in good yield instead of the expected 4-oxazolin-2-one (5a). The generality of the reaction and the mechanism are discussed.