Boron-Catalyzed Silylative Reduction of Nitriles in Accessing Primary Amines and Imines

Abstract

Silylative reduction of nitriles was studied under transition metal-free conditions by using B(C6F5)3 as a catalyst with hydrosilanes as a reductant. Alkyl and (hetero)aryl nitriles were efficiently converted to primary amines or imines under mild conditions. The choice of silanes was found to determine the selectivity: while a full reduction of nitriles was highly facile, the use of sterically bulky silanes allowed for the partial reduction leading to N-silylimines.

Selective Metal‐Free Hydrosilylation of CO2 Catalyzed by Triphenylborane in Highly Polar, Aprotic Solvents

“…Notably,o nly one of the two siliconhydride bonds in PhMeSiH 2 reacteds electively. [12] Whereas the 3 SiH and polymethylhydrosiloxane (PMHS;T able 2, entries 4a nd 5) remained unreacted under the same conditions, for reasons that are currently unknown.…”

Hydrogen Atom Transfer‐Mediated Cyclisations of Nitriles

“…In this work (Scheme b), we show that the scope of HAT‐mediated cyclisation reactions can be expanded to exploit nitriles as radical acceptors, despite potential issues such as β‐scission and competing alkene/nitrile reduction pathways …”

“…In this work (Scheme 1b), we show that the scopeo fH ATmediated cyclisation reactions can be expanded to exploit nitriles as radicala cceptors, despite potentiali ssues such as bscission [24] and competing alkene/nitrile reduction pathways. [25] During studies of conventional hydrofunctionalisation chemistry with alkene-nitrile 1,a ni nteresting observation was made( Scheme 2). Rather than the radicali ntermediate A reacting with the electrophilic radicophile Ts CN in an intermolecular fashion,l eading to product B,t he radicalw as trapped in a6 - exo-dig cyclisation to afford imine C.D ihydroquinolinone 2 was subsequently isolatedf rom the reactionm ixture upon treatment with aqueous acid (see below).…”

Selective Hydrogenation of Nitriles to Primary Amines Catalyzed by a Polysilane/SiO2‐Supported Palladium Catalyst under Continuous‐Flow Conditions

“…However, the reactiong enerally suffers from limited substrate scope and low selectivity.Aseriousi ssue is the formation of side products such as secondary and tertiary amines. [8] Whereas homogeneous catalysts based on precious metals such as Ir,R h, and Ru with complex ligands have often been employed, [9] quite recently Beller et al and Milstein et alindependently developed abundant and less toxic Fe, Co, and Mn catalysts for the selective hydrogenation of nitrilest op rimary amines. [10] On the other hand, heterogeneous catalysts have advantages over homogeneous catalysts in terms of the separation of catalysts and products as well as the recovery and reuse of catalysts.…”

“…However, the reactiong enerally suffers from limited substrate scope and low selectivity.Aseriousi ssue is the formation of side products such as secondary and tertiary amines. [8] Whereas homogeneous catalysts based on precious metals such as Ir,R h, and Ru with complex ligands have often been employed, [9] quite recently Beller et al and Milstein et al…”