Polarity Inversion of Donor-Acceptor Cyclopropanes: Disubstituted δ-Lactones via Enantioselective Iridium Catalysis

The coupling of carbonyl electrophiles at the donor position of donor acceptor cyclopropanes is described, representing an inversion of polarity with respect to conventional reactivity modes displayed by these reagents. Specifically, upon exposure of donor-acceptor cyclopropanes to alcohols in the presence of a cyclometalated iridium catalyst modified by (S)-BINAP, catalytic C-C coupling occurs, providing enantiomerically enriched products of carbonyl allylation. Identical products are obtained upon isopropanol-mediated transfer hydrogenation of donor acceptor cyclopropanes in the presence of aldehydes. The reaction products are directly transformed to cis-4, 5-disubstituted delta-lactones.