Organic chemistry. Rh-catalyzed C-C bond cleavage by transfer hydroformylation
Stephen K Murphy1, Jung-Woo Park2, Faben A Cruz2
1Department of Chemistry, University of California Irvine, CA 92697-2025, USA. Department of Chemistry, University of Toronto, Ontario M5S 3H6, Canada.
Abstract:
The dehydroformylation of aldehydes to generate olefins occurs during the biosynthesis of various sterols, including cholesterol in humans. Here, we implement a synthetic version that features the transfer of a formyl group and hydride from an aldehyde substrate to a strained olefin acceptor. A Rhodium (Xantphos)(benzoate) catalyst activates aldehyde carbon-hydrogen (C-H) bonds with high chemoselectivity to trigger carbon-carbon (C-C) bond cleavage and generate olefins at low loadings (0.3 to 2 mole percent) and temperatures (22° to 80°C). This mild protocol can be applied to various natural products and was used to achieve a three-step synthesis of (+)-yohimbenone. A study of the mechanism reveals that the benzoate counterion acts as a proton shuttle to enable transfer hydroformylation.
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