Aluminum-Catalyzed Selective Hydroboration of Nitriles and Alkynes: A Multifunctional Catalyst

Abstract

The reaction of LH [L = {(ArNH)(ArN)-C=N-C=(NAr)(NHAr)}; Ar =2,6-Et₂-C₆H₃] with a commercially available alane amine adduct (H₃Al·NMe₂Et) in toluene resulted in the formation of a conjugated bis-guanidinate (CBG)-supported aluminum dihydride complex, i.e., LAlH₂ (<b>1</b>), in good yield. The new complex has been thoroughly characterized by multinuclear magnetic resonance, IR, mass, and elemental analyses, including single-crystal structural studies. Further, we have demonstrated the aluminum-catalyzed hydroboration of a variety of nitriles and alkynes. Moreover, aluminum-catalyzed hydroboration is expanded to more challenging substrates such as alkene, pyridine, imine, carbodiimide, and isocyanides. More importantly, we have shown that the aluminum dihydride catalyzed both intra- and intermolecular chemoselective hydroboration of nitriles and alkynes over other reducible functionalities for the first time.