THE EFFECT OF THE RING SIZE OF THE DITHIOLATO LEAVING GROUP ON THE ORIENTATION OF BETA-ELIMINATION IN THE NICKEL-CATALYZED ALKENATION OF CYCLIC DITHIOACETALS WITH ME3SICH2MGCL

The product distribution (allyl- vs. vinyl-silanes) of the reactions of dithioacetals derived from alkyl aryl ketones with Me3SiCH2MgCl surprisingly depends on ring size of the cyclic dithioacetals, the five-membered ring substrates affording allylsilane as the major product while the six-membered analogues yield vinylsilanes predominantly. These results indicate that the leaving group, dithiolato moiety, may remain coordinated to the metal centre during the course of the catalytic process.