Carbon-carbon bond formation via boron mediated transfer

Organoboron chemistry continues to make an ever-increasing impact on general methodology in synthetic organic chemistry. Over the recent years advances in the reduction, hydroboration, and coupling protocols have served to broaden the synthetic chemists' arsenal with methods illustrating the utility of boron. If one were to include boron enolate chemistry in conjunction with the previously mentioned areas this would encompass most of the literature related to organoboron chemistry. What remains paramount to the synthetic organic chemist are those synthetic methods that result in the formation of carbon-carbon bonds. With respect to organoboron chemistry, the most widely used methods (reduction and hydroboration) do not result in carbon-carbon bond formation. Although boron enolate chemistry and Suzuki based coupling reactions result in the formation of carbon-carbon bonds, it could be argued that boron is not directly involved in the formation of these bonds. However, there exists an area of organoboron chemistry that has been sporadically visited but has yet to be categorized. What is presented here is a review of the carbon-carbon bond forming reactions that are mediated through direct transfer of an appendage from boron to result in a new carbon-carbon bond. This review of boron mediated transfer reactions is not meant to be exhaustive, but it does span similar to40 years in an attempt to assemble a number of examples that best illustrate this category, and to provide a template for substantial expansion of this area.