Heterofunctional control of regio- and enantioselectivity in rhodium-catalysed hydroboration of allylic systems

Aryl allylic sulfones were reacted with catecholborane (HBcat) in the presence of neutral and cationic Rh complexes modified with bidentate chiral ligands, to produce the branched heteroorganoboronate ester, as the main isomer with moderate enantioselectivity. The relative rate of the formation of the secondary regioisomer seems to be sensitive to the nature of the catalytic system and the electronic effects of the substrate.