Catalytic Enantioselective Protoboration of Disubstituted Allenes. Access to Alkenylboron Compounds in High Enantiomeric Purity
作者:Hwanjong Jang、Byunghyuck Jung、Amir H. Hoveyda
DOI:10.1021/ol5022417
日期:2014.9.5
Proto-boryl additions to 1,1-disubstituted allenes in the presence of 1.0–5.0 mol % of chiral NHC–Cu complexes, B2(pin)2, and t-BuOH proceed to afford alkenyl–B(pin) products in up to 98% yield, >98:2 site selectivity, and 98:2 er. The enantiomerically enriched alkenylboron products can be converted to otherwise difficult-to-access alkenyl bromides, methylketones or carboxylic acids. What’s more,
Alkynylalanes were found to react efficiently with propargylic electrophiles, such as propargyl mesylates and propargyl diethylphosphates. The reaction proceeds with high regioselectivity and does not require copper or any other transition metal.