SUBSTRATE-DIRECTED DIASTEREOSELECTIVE HYDROFORMYLATIONS .1. SUBSTRATE-DIRECTED DIASTEREOSELECTIVE HYDROFORMYLATION OF METHALLYLIC ALCOHOLS - DEVELOPMENT OF AN EFFICIENT CATALYST-DIRECTING GROUP FOR RHODIUM-CATALYZED HYDROFORMYLATION

The development of an efficient catalyst-directing group based on orth o-diphenylphosphanyl benzoate (o-DPPB) for the substrate-directed, dia stereoselective hydroformylation of methallylic alcohols 5 is describe d. The hydroformylation of methallylic o-DPPB esters 9 provides the co rresponding syn-aldehydes 10 with diastereoselectivities of up to 96:4 . A specific steric demand of the substituent at the stereogenic cente r of the methallylic derivatives 9 was found to be necessary to achiev e a high degree of stereoselectivity. Experiments have been performed that prove that the o-DPPB group acts as a catalyst-directing group by reversibly coordinating to the catalyst. The removal of the o-DPPB gr oup was accomplished by means of alkaline hydrolysis, thereby furnishi ng the lactols 6. Oxidation of 6 provides the corresponding gamma-lact ones 7.