Cross-coupling of organoboronic acids and sulfinate salts using catalytic copper(II) acetate and 1,10-phenanthroline: synthesis of aryl and alkenylsulfones

A mild method for the preparation of aryl and alkenylsulfones from the cross-coupling reaction of organoboronic acids and sodium sulfinate salts is described. Optimized conditions utilize a catalytic amount of copper(II) acetate monohydrate with 1,10-phenanthroline as ligand in the presence of 4 Å molecular sieves. A co-solvent mixture of dichloromethane/DMSO was used, with reactions occurring at 40 °C under an atmosphere of oxygen. Reaction at room temperature also yields sulfone product, but in lower yields. The method tolerates a variety of substituents on the organoboronic acid, including amide, aldehyde, halide and nitro functionalities, as well as ortho-substituents. In general, the reaction is found to be less efficient using arylboronic acids bearing electron-withdrawing substituents, or using aryltrifluoroborate salts.