Rh(III)-catalyzed diastereoselective C-H bond addition/cyclization cascade of enone tethered aldehydes

The Rh(III)-catalyzed cascade addition of a C-H bond across alkene and carbonyl pi-bonds is reported. The reaction proceeds under mild reaction conditions with low catalyst loading. A range of directing groups were shown to be effective as was the functionalization of alkenyl in addition to aromatic C(sp(2))-H bonds. When the enone and aldehyde electrophile were tethered together, cyclic beta-hydroxy ketones with three contiguous stereocenters were obtained with high diastereoselectivity. The intermolecular three-component cascade reaction was demonstrated for both aldehyde and imine electrophiles. Moreover, the first X-ray structure of a cationic Cp*Rh(III) enolate with interatomic distances consistent with an eta(3)-bound enolate is reported.