Stereospecificity in (2 + 2) Cycloaddition of Benzyne and Ketene Silyl Acetal.

Abstract The first observation of the stereospecificity in the benzyne-olefin [2 + 2] cycloaddition is described. The key points reside in (1) the efficient method for generating benzyne species by the halogen-lithium exchange reaction of ortho -halo aryl triflates, and (2) the choice of ketene silyl acetal as the partner olefin.