Synthetic variations based on low-valent chromium: new developments

This article presents an overview of the synthetic chemistry of low-valent chromium, presumably Cr(II) species, and highlights most of the recent deve lopments. These organometallic reactions represent a convenient strategy fo r the construction of carbon-carbon bonds displaying unique elements of ste reocontrol, chemoselectivity, and functional-group compatibility. The intro duction of milder protocols, catalytic versions, and the discovery of ligan d tuning effects as a means of controlling carbanion selectivity, are the m ost salient improvements in this expansive field.