Regioselective catalytic hydroboration of propargylic species using Cu(I)-NHC complexes.

The catalytic regioselective hydroboration of propargylic alcohols and ethers was investigated using NHC-CuCl. We observe that different NHC-CuCl complexes catalyze hydroborations of propargylic substrates with opposite regioselectivity. A 6-NHC-CuCl complex provides α-selectivity whereas β-selectivity is achieved using a 5-NHC-CuCl complex. The reaction tolerates a wide range of functional groups.