Reactions with dialkoxyboryl-stabilized carbanions

The reactions of epoxides with dialkoxyboryl-stabilized carbanions are complicated by interaction of the oxyanion produced with the dialkoxyboryl grouping. When such an interaction is sterically inhibited, as with cyclohexene oxide, a single product results (equation 32). ... 

In reactions with benzophenone and cyclohexanone the dialkoxyboryl-stabilized carbanions still eliminate silicon but the dimesitylboryl derivatives eliminate boron and silicon competitively so that a mixture of products results. ... 

Tris(dialkoxyboryl)alkanes such as (8), produced as in equation (4), may also be used as precursors of boron-stabiliz carbanions. Reaction of (8) with base gives (9), which is stabilized by two boron atoms (equation 5). It is not clear whether a similar reaction succeeds with CH2[B(OR)2]2. 

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