THE REGIOCHEMISTRY AND STEREOCHEMISTRY OF ALPHA,BETA-EPOXYSILANE RING-OPENING WITH SILYL HALIDES OR PSEUDOHALIDES

The reaction of trimethylsilyl halides with alpha,beta-epoxysilanes le ads to either a vinyl halide by addition/elimination or a vinyl enol e ther by rearrangement; the route depends upon the nature of the groups attached to the epoxide ring. With groups beta to the silicon that ca n stabilise an adjacent positive charge the directive effect of silico n towards substitution at the alpha position is overcome such that the enol ether is obtained. Trimethylsilyl pseudohalides behave similarly except that the intermediate addition product can be isolated. The st ereoselectivity of ring opening is found to vary with the reagent.