Supramolecular Control of Selectivity in Hydroformylation of Vinyl Arenes: Easy Access to Valuable β-Aldehyde Intermediates†

A rationally designed regioselective formylation catalyst, in which noncovalent ligand-​substrate interactions allow the unprecedented reversal of selectivity from the typical α-​aldehyde to the otherwise unfavored β-​aldehyde, is reported. Thus, hydroformylation of o-​vinyl arene(or heteroarene)​carboxylic acids, e.g. I (R = 4-​Me, 6-​Me, 5-​O2N, 3,​4-​benzo, 5,​6-​OCH2O, etc.)​, with syngas in dichloromethane in the presence of this newly developed catalytic system and a base afforded the corresponding aldehydes, e.g. II, with excellent regioselectivity and high chemoselectivity towards aldehydes.