Rhodium-catalyzed regioselective addition of the ortho C-H bond in aromatic amides to the C-C double bond in α,β-unsaturated γ-lactones and dihydrofurans

An unprecedented C-H alkylation using alpha,beta-unsaturated gamma-lactones (butenolides) and dihydrofurans was achieved by the Rh-catalyzed reaction of benzamides. C-C bond formation occurs between the ortho-position of the benzamide derivative and the gamma-position of the butenolide or the a-position of the dihydrofuran. The presence of an 8-aminoquinoline directing group is crucial for the success of the reaction. The results of deuterium labeling experiments indicate that the cleavage of the C-H bond is reversible and suggest that a migratory carbene insertion is involved as the key step.