Hydroformylation of Aryloxy Ethylenes by Rh/BINAPHOS Complex.Catalyst Deactivation Path and Application to the Asymmetric Synthesis of 2-Aryloxypropanoic Acids

The behavior of Rh(I)/(S,R)-BINAPHOS complex in the asymmetric hydroformylation of styrene and other aryloxy substituted ethylenes shows a sharp deterioration in stereocontrol as the conversion increases. This failure is apparently due to an irreversible reaction of the starting complex with the aldehyde which is built up in solution and its extent can be limited operating at short contact times and low temperatures. Under optimized conditions, the hydroformylation of aryloxy substituted ethylenes provides the relevant branched aldehyde in some 70% regioselectivity and in up to 80% ee.