HYDROFORMYLATION OF STYRENE USING THIOLATO-PYRAZOLATE BRIDGE RHODIUM CATALYSTS MODIFIED WITH PHOSPHORUS LIGANDS

Catalytic precursor systems prepared using [Rh-2(mu-pz)(mu-SBut)(COD)( 2)] in the presence of triphenylphosphine and chiral diphosphines are active in styrene hydroformylation. The effect of the pressure and the dependence on the P/Rh ratio are studied. When triphenylphosphine is used as phosphorous ligand complete conversion to aldehydes and regios electivities as high as 90% in 2-phenylpropanal are obtained at very m ild conditions. The use of (+)-(2R,4R)( -)-(2S,4S)-2,4-bis(diphenylpho sphino)pentane ((+)-BDPP) or (-)-(2S,4S) ((-)-BDPP) as chiral diphosph ine in a P/Rh ratio of 2 provides 95% regioselectivity and enantiomeri c excess as high as 50%. (C) 1998 Elsevier Science B.V. All rights res erved.