title: Mechanistic insights into hydroacylation with non-chelating aldehydes†Electronic supplementary information (ESI) available: Materials and methods, reaction procedures, characterization data. CCDC 1012849. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4sc02026jClick here for additional data file.
abstract: The combination of a small-bite-angle diphosphine bis(dicyclohexylphosphino)methane (dcpm) and [Rh(cod)OMe]2catalyses the hydroacylation of 2-vinylphenols with a wide range of non-chelating aldehydes. Here we present a detailed experimental study that elucidates the factors contributing to the broad aldehyde scope and high reactivity. A variety of catalytically relevant intermediates were isolated and a [Rh(dcpm)(vinylphenolate)] complex was identified as the major catalytically relevant species. A variety of off-cycle intermediates were also identified that can re-enter the catalytic cycle by substrate- or 1,5-cyclooctadiene-mediated pathways. Saturation kinetics with respect to the 2-vinylphenol were observed, and this may contribute to the high selectivity for hydroacylation over aldehyde decarbonylation. A series of deuterium labelling experiments and Hammett studies support the oxidative addition of Rh to the aldehyde C-H bond as an irreversible and turnover-limiting step. The small bite angle of dcpm is crucial for lowering the barrier of this step and providing excellent reactivity with a variety of aldehydes.
authors.affiliation: Department of Chemistry , University of California , Irvine , California 92697-2025 , USA . Email: dongv@uci.edu ; Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , Ontario M5S 3H6 , Canada.
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Murphy
authors.affiliation: Department of Chemistry , University of California , Irvine , California 92697-2025 , USA . Email: dongv@uci.edu.
authors.forename: Achim
authors.initials: A
authors.lastname: Bruch
authors.affiliation: Department of Chemistry , University of California , Irvine , California 92697-2025 , USA . Email: dongv@uci.edu.
authors.forename: Vy M
authors.initials: VM
authors.lastname: Dong