Effect of chiral diene ligands in rhodium-catalyzed asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds.

Asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of the addition products with high enantioselectivity (96->99.5% ee). The diene ligand was proved to be essential for the formation of the addition products, while the use of a bisphosphine ligand mainly gave the cine-substitution product.