SYNTHESIS VIA VINYL SULFONES .73. FREE-RADICAL SELF-IMMOLATIVE 1,2-ELIMINATION AND REDUCTIVE DESULFONYLATION OF ARYL SULFONES PROMOTED BY INTRAMOLECULAR REACTIONS WITH ORTHO-ATTACHED CARBON-CENTERED RADICALS

Aryl sulfones bearing an o-(bromomethyl)dimethylsilyl moiety (1), when heated with AIBN and tributyltin hydride, suffer radical elimination under mild conditions to give olefins and stannyl sulfinate 7 in high yield. The mechanism is shown to proceed via intramolecular beta-sulfo nyl hydrogen abstraction by o-silylmethylene radical 2, This step also shows a large deuterium isotope effect of 12:1. In contrast, radical intermediate 24, generated by tris(trimethylsilyl)silane radical addit ion to o-allylsilane 23, undergoes intramolecular attack on the sulfon e, resulting in homolytic sulfone cleavage to afford reduced products and cyclic sulfone byproduct 25.