CHARACTERIZATION AND APPLICATION OF CATALYTIC REGIOSELECTIVE HYDROFORMYLATION WITH A CATIONIC BIS(DIOXAPHOSPHOLANE)RHODIUM CATALYST PRECURSOR

A cationic rhodium complex containing a bis(dioxaphospholane) ligand i s very effective in regioselective hydroformylation. Aryl olefin subst rates are hydroformylated with very high rates (>3000 turnovers per Rh per hour) and high regioselectivity (>92:8 for branched products). Wi th smaller substrate:catalyst ratios higher regioselectivity (higher t han 97:3) is found, and control and mass balance experiments indicate this is caused by selective decomposition of the linear aldehyde produ ct. Very good regioselectivity is also found with methyl acrylate. Mod est regioselectivity is obtained with terminal alkyl olefins. The effi cient hydroformylation of 2,6-dimethylstyrene is consistent with the a bsence of pi-benzyl intermediates in this catalyst system. The applica tion of regioselective hydroformylation in organic synthesis is develo ped to give a new route to a racemic intermediate to alpha-cuparenone. The efficient synthesis of 3-methylindole from o-vinylaniline by hydr oformylation/dehydration is described, alongwith a similar annulation of o-vinylacetophenone.