gem-Difluorosubstituted NH-azomethine ylides in the synthesis of 4-fluorooxazolines via the three-component reaction of imines, trifluoroacetophenones and CF2Br2

A simple one-step synthesis of a new class of fluorinated heterocycles, 4-fluoro-3-oxazolines, from diarylmethanimines, trifluoroacetophenones and CF2Br2 is described. The reaction proceeds via the sequential formation of difluorocarbene and a gem-difluorosubstituted NH-azomethine ylide, followed by 1,3-dipolar cycloaddition with a ketone.