Catalytic hydrogen atom transfer from hydrosilanes to vinylarenes for hydrosilylation and polymerization

Abstract

Because of the importance of hydrogen atom transfer (HAT) in biology and chemistry, there is increased interest in new strategies to perform HAT in a sustainable manner. Here, we describe a sustainable, net redox-neutral HAT process involving hydrosilanes and alkali metal Lewis base catalysts—eliminating the use of transition metal catalysts—and report an associated mechanism concerning Lewis base-catalysed, complexation-induced HAT. The catalytic Lewis base-catalysed, complexation-induced HAT is capable of accessing both branch-specific hydrosilylation and polymerization of vinylarenes in a highly selective fashion, depending on the Lewis base catalyst used. In this process, the Earth-abundant, alkali metal Lewis base catalyst plays a dual role. It first serves as a HAT initiator and subsequently functions as a silyl radical stabilizing group, which is critical to highly selective cross-radical coupling. An electron paramagnetic resonance study identified a potassiated paramagnetic species, and multistate density functional theory revealed a high HAT character, yet multiconfigurational nature in the transition state of the reaction.

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Fig. 1: Strategies for the hydrofunctionalization of unsaturated bonds involving transition metal hydride and hypercoordinate silicon hydride catalysis.
Fig. 2: Proposed mechanism for LBCI-HAT.
Fig. 3: Optimization and mechanistic investigation of LBCI-HAT.
Fig. 4: Hydrogen atom trapping experiments.
Fig. 5: Spectroscopic studies for LBCI-HAT.
Fig. 6: Computed reaction energy profile for LBCI-HAT reactions.
Fig. 7: Scope of the branch-selective hydrosilylation involving LBCI-HAT.

Data availability

All data supporting the findings of this study, including experimental details, spectroscopic characterization data for all compounds, and computational details, are available within the paper and its Supplementary Information, or from the corresponding author upon reasonable request.

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Acknowledgements

We are grateful for financial support from the National Institutes of Health (NIGMS; GM116031 to J.J. and GM117511-01 to B.S.P.), ACS Petroleum Research Fund (PRF number 54831-DNI1 to J.J.), National Science Foundation (CHE; 1709369 to B.S.P.), Swedish Research Council (VR 2015-04114 to K.N.) and University of Texas at Arlington (to K.N.). We acknowledge the NSF (CHE-0234811 and CHE-0840509) for partial funding of the purchases of the NMR spectrometers used in this work.

Author information

P.A., Y.H. and J.J. conceived the project, designed the experiments and wrote the manuscript. P.A. and Y.H. performed the NMR and gas chromatography studies. Y.H., P.A., A.B., C.T. and W.P. further developed the reaction and expanded the scope. Y.H. performed the radical clock and corresponding control experiments. B.S.P., P.A. and S.S. performed the EPR studies. J.G., K.N. and X.C. conducted the computational studies. G.L., P.A., K.Y. and A.K. carried out the synthesis and analysis of polymers. All authors discussed the results and commented on the manuscript.

Correspondence to Junha Jeon.

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Supplementary Information

Supplementary Methods, Supplementary Discussion, Supplementary Figures 1–29, Supplementary Tables 1–7, Supplementary References

Supplementary Data 1

Cartesian coordinates

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Asgari, P., Hua, Y., Bokka, A. et al. Catalytic hydrogen atom transfer from hydrosilanes to vinylarenes for hydrosilylation and polymerization. Nat Catal 2, 164–173 (2019) doi:10.1038/s41929-018-0217-z

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