Synlett 2017; 28(18): 2411-2414
DOI: 10.1055/s-0036-1588441
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© Georg Thieme Verlag Stuttgart · New York

Exhaustive Chemoselective Reduction of Nitriles by Catalytic Hydrosilylation Involving Cooperative Si–H Bond Activation

Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 115, 10623 Berlin, Germany   eMail: martin.oestreich@tu-berlin.de
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Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 115, 10623 Berlin, Germany   eMail: martin.oestreich@tu-berlin.de
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This research was supported by the Deutsche Forschungsgemeinschaft (Oe 249/10-1). M.O. is indebted to the Einstein Foundation (Berlin) for an endowed professorship
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Publikationsverlauf

Received: 09. März 2017

Accepted after revision: 09. Mai 2017

Publikationsdatum:
31. Mai 2017 (online)


Published as part of the Cluster Silicon in Synthesis and Catalysis

Abstract

A chemoselective method for the catalytic hydrosilylation of nitriles to either the imine or amine oxidation level is reported. The chemoselectivity is controlled by the hydrosilane used. The usefulness of the nitrile-to-amine reduction is demonstrated for a diverse set of aromatic and aliphatic nitriles, and the amines are easily isolated after hydrolysis as their hydrochloride salts. This exhaustive nitrile reduction proceeds at room temperature.

Supporting Information

 
  • References and Notes

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    • 3a Wünsch B. Geiger C. In Science of Synthesis . Vol. 40a. Schaumann E. Thieme; Stuttgart: 2009: 38
    • 3b Wünsch B. Geiger C. In Science of Synthesis . Vol. 40a. Schaumann E. Thieme; Stuttgart: 2009: 41
  • 4 Wünsch B. Geiger C. In Science of Synthesis . Vol. 40a. Schaumann E. Thieme; Stuttgart: 2009: 29
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  • 11 A similar observation where the chemoselectivity is controlled by the reaction temperature (25 °C vs. 100 °C) was made by Stephan and co-workers before: Perez M. Qu Z.-W. Caputo CB. Podgorny V. Hounjet LJ. Hansen A. Dobrovetsky R. Grimme S. Stephan DW. Chem. Eur. J. 2015; 21: 6491
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  • 18 Enolizable ketones16b and imines16d are initially converted into silyl enol ethers and N-silyl enamines, respectively, but undergo at prolonged reaction times subsequent hydrogenation with the dihydrogen released in the preceding dehydrogenative coupling step.17c,d
  • 19 For a synthetic and mechanistic study of hydrogenation catalyzed by [3a] + [BArF 4], see: Lefranc A. Qu Z.-W. Grimme S. Oestreich M. Chem. Eur. J. 2016; 22: 10009
  • 20 General Procedure for Nitrile-to-Amine Reduction In a glove box, a flame-dried GLC vial equipped with a magnetic stir bar is charged with [3a]+[BArF 4] (1.0 mol%) and Me2PhSiH (2a, 2.1 or 5.0 equiv). The indicated nitrile is added either in the glove box (for solid starting materials) or by microsyringe outside the glove box, and the resulting reaction mixture is maintained at r.t. for the indicated time. The reaction is quenched by the addition of a mixture of cyclohexane and tert-butyl methyl ether (90:10) containing 4% Et3N (0.5 mL), and the resulting solution is filtered through a pad of Celite® coated by a small layer of silica gel with a solution of cyclohexane and tert-butyl methyl ether (90:10) containing 4% Et3N (3–4 mL) as eluent. Solvents are removed under reduced pressure, and the residue is dissolved in Et2O (1 mL) followed by addition of HCl (2 M in Et2O, 1.0 mL, 2.0 mmol, 10 equiv). The resulting suspension is stirred for 1 h and filtered, affording the amines as hydrochloride salts as white to yellow solids.
  • 21 General Procedure for Nitrile-to-Imine Reduction In a glove box, a flame-dried GLC vial equipped with a magnetic stir bar is charged with [3a]+[BArF 4] (1.0 mol%), Et3SiH (2b, 2.0 equiv), and mesitylene (10 μL, 8.7 mg, 0.20 mmol, internal standard). The indicated nitrile is added either in the glove box (for solid starting materials) or by microsyringe outside the glove box, and the resulting reaction mixture is maintained at r.t. for 18 h. The mixture is then dissolved in CD2Cl2 (0.6 mL) and transferred into a NMR tube. 1H NMR spectroscopy is used to determine the yield with reference to mesitylene.