The Selective and Partial Reduction of Nitriles Was Achieved Through the Generation of Dichloroindium Hydride via the Reduction of Indium Trichloride With Either: Sodium Borohydride, Diisobutylaluminum Hydride, or Lithium Aminoborohydride

The in situ generation of dichloroindium hydride (HInCl₂) via the reduction of indium trichloride (InCl₃) with stoichiometric amounts of either: sodium borohydride (NaBH₄), diisobutylaluminum hydride (DIBAL-H), or lithium aminoborohydride (LAB) in tetrahydrofuran (THF) and acetonitrile (CH₃CN) was studied. These reduction systems were then explored for the selective reduction of various functionalized aromatic and aliphatic compounds under mild reaction conditions. Depending on the strength of the reducing agent used, varying amounts of indium metal zero were observed during the reduction of InCl₃. Alternatively, production of HInCl₂ using NaBH₄ did not produce indium metal zero. Our goal was to investigate the capabilities of HInCl₂, generated by different methods, in the selective reduction of multi-functionalized compounds containing carbonyls, nitriles, and halogens. Based on the method of generation, HInCl₂ was able to selectively and/or partially reduce p-haloalkyl benzonitriles to either p-methyl benzonitrile, p-methyl benzamine, p-halomethyl benzamine, p-halomethyl benzaldehyde, or p-tolualdehyde in yields ranging from 70-90%. Reactions were monitored and characterized by thin layer chromatography, IR, ¹¹B, ¹H, and ¹³C NMR spectroscopy. Preliminary results suggest that HInCl₂ can be used in tandem with a variety of other reducing agents to achieve selective reduction of various functional groups.