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

摘要

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 cyclometallated iridium catalyst modified by (S)-BINAP, catalytic C-C coupling occurs to provide 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 δ-lactones.