Boron-Wittig olefination with gem-bis(boryl)alkanes.

The condensation of easy manageable lithium α-bis(boryl)carbanions with carbonyl derivatives, the so-called boron-Wittig reaction, allows for the straightforward and often stereoselective formation of synthetically highly versatile metalloid-substituted alkenes, which are key building blocks on route to all-carbon substituted olefins. In this Tutorial review the concept behind this olefination reaction and its application to ketones, aldehydes and other carbonyl derivatives, such amides, ester and carboxylic acids, are presented in a systematic manner. A special emphasis has been placed on parameters controlling the stereochemical outcome of these transformations. To illustrate the great synthetic potential of this new methodological tool, a section is also included covering a selection of applications of the boron-Wittig reaction to target compounds via subsequent C-C bond-forming process.