Stereoselective Unsymmetrical 1,1-Diborylation of Alkynes with a Neutral sp -sp Diboron Reagent.

The incorporation of two distinct boryl groups at the same carbon center in organic molecules has attracted growing research interest due to its potential for facilitating controlled, precise synthesis through stepwise dual carbon-boron bond transformations. Here we report a method to access unsymmetrical 1,1-diborylalkene (UDBA) stereoselectively via the reaction of readily available alkynes with a neutral sp -sp diboron reagent (NHC)BH -Bpin (NHC=N-heterocyclic carbene). Attributing to the chemically easily distinguishable nature of the sp and sp boryl moieties, controllable stepwise derivatization of the resultant UDBAs is realized. This process leads to various multifunctionalized olefins and organoborons, such as acylboranes, which are difficult to prepare by other methods.