Rhodium-catalyzed [4+2] Coupling Reactions of Cyclobutanones with Olefins through the C—C Bond Activation

Dong et al. have reported the catalytic [4+2] coupling reactions of cyclobutanones with olefins through C—C bond activation. According to their results, the cyclobutanone tethered with olefin (1) is smoothly converted into the corresponding 3-azabicyclo[3.3.1]nonanone (2) catalyzed by [Rh(C₂H₄)₂Cl]₂ catalyst with addition of tris[3,5-bis(trifluoromethyl)phenyl]phosphine ligand and 2-amino-3-picoline as a cofactor. The carbonyl group of the product can be converted into other functional groups or ring systems to provide a range of bridged skeletons. Since bridged ring systems are widely found in natural products, this methodology is expected to be applied in the synthesis of complex natural products and other bioactive molecules.