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/c4sc02026j Click here for additional data file. Click here for additional data file
| Autor: | Murphy, Stephen K., Bruch, Achim, Dong, Vy M. |
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| Jazyk: | angličtina |
| Rok vydání: | 2014 |
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| Zdroj: | Chemical Science |
| ISSN: | 2041-6539 2041-6520 |
| Popis: | Rhodium catalysts with small-bite-angle diphosphines enable branched-selective hydroacylation of 2-vinylphenols via C–H activation of non-chelating aldehydes. The combination of a small-bite-angle diphosphine bis(dicyclohexylphosphino)methane (dcpm) and [Rh(cod)OMe]2 catalyses 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. |
| Databáze: | OpenAIRE |
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