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

A cationic rhodium complex containing a bis(dioxaphospholane) ligand is very effective in regioselective hydroformylation. Aryl olefin substrates are hydroformylated with very high rates (>3000 turnovers per Rh per hour) and high regioselectivity (>92:8 for branched products). With smaller substrate:catalyst ratios higher regioselectivity (higher than 97:3) is found, and control and mass balance experiments indicate this is caused by selective decomposition of the linear aldehyde product. Very good regioselectivity is also found with methyl acrylate. Modest regioselectivity is obtained with terminal alkyl olefins. The efficient hydroformylation of 2,6-dimethylstyrene is consistent with the absence of pi-benzyl intermediates in this catalyst system. The application of regioselective hydroformylation in organic synthesis is developed to give a new route to a racemic intermediate to alpha-cuparenone. The efficient synthesis of 3-methylindole from o-vinylaniline by hydroformylation/dehydration is described, alongwith a similar annulation of o-vinylacetophenone.