Revisiting the reduction of indoles by hydroboranes: A combined experimental and computational study

TETRAHEDRON

卷:75

Article

Jayaraman, Arumugam¹  Powell-Davies, Henry²  Fontaine, Frederic-Georges¹ 

[1] Univ Laval, Dept Chim, 1045 Ave Med, Quebec City, PQ G1V 0A6, Canada

[2] Cardiff Univ, Sch Chem, Cardiff, S Glam, Wales

关键词: Indoles;    Hydroboration;    Frustrated Lewis pairs;    Hydroboranes;    Homogeneous catalysis;    Metal-free catalysis;   

DOI  :  10.1016/j.tet.2019.02.048

来源: Elsevier

【 摘 要 】

A combined experimental and density functional computational study was used to probe the mechanism for the reduction of indoles using simple borane BH3.DMS (DMS = dimethyl sulfide). Experimental and computational studies all steer to the formation of the reduced species 1-BH2-indolines as the resting state for this reaction, as opposed to the historically presumed formation of the unreduced 1-BH2-indoles, before the addition of a proton source to form the final product indolines. Furthermore, it was observed that molecular H-2 was generated and consumed in the reaction. Computations put forward hydroboration followed by protodeborylation as the very reasonable mechanistic route for the formation of experimentally observed major intermediate 1-BH2 indolines. For the H-2 consumption in the reaction, computations suggest the frustrated Lewis pair-type heterolytic splitting of H-2 by a bis(3-indolinyl)borane intermediate. (C) 2019 Elsevier Ltd. All rights reserved.

【 授权许可】

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