Nickel-catalyzed asymmetric reductive cross-couplings with vinyl bromide electrophiles

Abstract

Nickel-catalyzed reductive cross-coupling reactions allow for the use of bench-stable electrophiles as both cross-coupling partners. In an effort to broaden the range of viable substrates in asym. transformations, two new cross-coupling reactions using vinyl bromide electrophiles were developed. The cross-coupling of vinyl bromides with chlorobenzyl silanes in the presence of a chiral nickel bis(oxazoline) catalyst and stoichiometric manganese reductant delivers chiral allyl silane products with excellent enantioselectivity. These products are known to participate in diastereoselective allylation reactions that form addnl. stereocenters, building mol. complexity. Application of the same catalyst-ligand system to the cross-coupling of vinyl bromides with N-hydroxyphthalimide esters gives rise to chiral allylic stereocenters in the presence of tetrakis(dimethylamino)ethylene as a terminal org. reductant.