A Diastereomeric Pair of Sulfoxide-containing Chiral MOP-type Ligands: Preparation and Application to Rhodium-catalyzed Asymmetric 1,4-Addition Reactions

(R,SS)-Sulfoxide-MOP (L2) and (R,RS)-sulfoxide-MOP (L3) were developed as a diastereomeric pair of sulfoxide-containing chiral MOP-type ligands. These two ligands also represent the first monosulfoxide analogues of BINAP. The chiral ligand L2 was successfully applied to the highly enantioselective rhodium-catalyzed 1,4-addition between α,β-unsaturated ketones or esters and arylboronic acids, and exhibited a broad substrate scope when the reaction was performed using 1.5 mol% Rh in cyclohexane/H2O (10:1) at 40 °C under mild basic conditions.