Metal Substitutions of a-Haloalkyl boronic Esters

Pinacol (iodomethyl)boronate reacts with activated zinc to produce the synthetically useful zinc substituted boronic ester IZnCHjBfOjCjMeJ [89]. Several pinacol (a-bromoalkyl)boronates have also been converted into the zinc derivatives. These can be activated with copper salts and coupled with various electrophiles. 

A gem-bis(bromozinc) reagent, (BrZn)2CHB(02C2Me4), has been prepared from pinacol (dibromomethyl)boronate and zinc metal in the presence of a lead catalyst [92]. This reagent reacts with aldehydes in the presence of titanium tetrachloride to 

The utility of (a-haloalkyl)boronic esters as reagents for asymmetric synthesis is well established. A wide variety of products can be made in high stereopurity. This fundamental research has been supported for many years by the National Science Foim-dation, with periods of additional support from the National Institutes of Health. The discovery of the useful anticancer pharmaceutical Velcade , which is derived from an (a-aminoalkyl)boronic ester made from an (a-haloaIkyl)boronic ester, provides an example of the practical long-range benefits of support for fundamental research. 

Washburn, E. Levens, C. F. Albright, F. A. Billig, Organic Syntheses 1963, Coll. 

Shinomiya, H. Kaihara, N. Yoshida, T. Moriwake, Syrdett 1995, %3-964. 

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