o-Alkyl-substituted triphenyl phosphines: Activity and regioselectivity inrhodium-catalysed propene hydroformylation

Hydroformylation of propene is the most important hydroformylation process on the industrial scale. Typically, the aim has been the regioselective pro duction of the linear product n-butanal, Recently, interest in selective fo rmation of the branched aldehyde, isobutanal, has increased due to its use in the production of polyols, such as neopentyl glycol (2,2-dimethyl-1,3-pr opanediol). Study was made of the effect of o-alkyl-substituted triphenylph osphine ligands on the activity and regioselectivity in rhodium-catalysed p ropene hydroformylation. In addition, the effect of the process conditions on the activity and regioselectivity was investigated by varying the ligand -to-rhodium ratio (0-40), temperature (353-403 K), and deactivation for som e of the ligands. The results suggest that o-alkylsubstituted triphenylphos phine ligands enhance the selectivity to isobutanal. However, the activity decreases at the same time. A correlation was found between the P-31-NMR sh ifts of the ligands and the regioselectivity and activity: as the shift dec reases, the regioselectivity to isobutanal increases and the activity decre ases. Changes in the process conditions had an effect similar to that in th e reaction modified with triphenylphosphine. (C) 2001 Academic Press.