Stannyl anions alkenes

Methylenation of sulfones.1 This reagent reacts rapidly with the anion (LDA) of even moderately hindered sulfones to form (3-stannyl sulfones, which undergo desulfonylstannylation on treatment with Bu4NF to form alkenes. 

O-Stannyl ketyls have been proposed as intermediates for almost 30 years. Much of the early work came from the laboratories of Davies [9a], Pereyre [3, 9b, 9c] and Beckwith [6a, 10] and provided a framework for a modern understanding of O-stannyl ketyls. These seminal studies were often focussed on mechanistic aspects of tin ketyls in a-cyclopropyl- and a-epoxy-ketone ring openings. In one of the first carbonyl-alkene cyclizations, it was determined that the tributyltin radical added to a ketone in a somewhat sluggish manner and that excess amounts of tin hydride were needed to drive the reaction to completion [6a]. It was also understood that a ketyl radical anion is more stable than a simple carbon-centered radical, likely attributed to more effective delocalization. Ketyl reactive intermediates are now being utilized in new strained-ring cleavage-recyclization sequences (see below) and are... 

Although 0-stannyl ketyl radical anions are intermediates only recently developed for synthetic applications, they already provide ready access to carbonyl-alkene cyclizations, ring scissions, and tin(IV) enolates. Unlike standard radical reactions, these transformations provide an alcohol or ketone after workup that can be further synthetically manipulated. Finally, the intermediates can be applied to natural product skeletons such as the triquinanes. 

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