Despite the wide use and popularity of metal hydride catalysis, methods utilizing zirconium hydride catalysts remain underexplored. Here, we report the development of a mild method for the in situ preparation and use of zirconium hydride catalysts. This robust method requires only 2.5−5 mol % of zirconocene dichloride in combination with a hydrosilane as the stoichiometric reductant and does not require careful air-or moisture-free techniques. A key finding of this study concerns an amine-mediated ligand exchange en route to the active zirconocene hydride catalyst. A mechanistic investigation supports the intermediacy of an oxo-bridged dimer precatalyst. The application of this method to the reduction of a wide variety of carbonylcontaining substrates, including ketones, aldehydes, enones, ynones, and lactones, is demonstrated with up to 92% yield and exhibits broad functional group tolerability. These findings open up alternative avenues for the catalytic application of chlorozirconocenes, potentially serving as the foundation for broader applications of zirconium hydride catalysis.

The mild catalytic partial reduction of amides to imines has proven to be a challenging synthetic transformation, with many transition metals directly reducing these substrates to amines. Herein, we report a mild, catalytic method for the semireduction of both secondary and tertiary amides via zirconocene hydride catalysis. Utilizing just 5 mol % of Cp 2 ZrCl 2 , the reductive deoxygenation of secondary amides is demonstrated to furnish a diverse array of imines in up to 94% yield with excellent chemoselectivity and without the need for glovebox handling. Moreover, a novel reductive transamination of tertiary amides is also achievable when the catalytic protocol is carried out in the presence of a primary amine at room temperature, providing access to an expanded assortment of imines in up to 98% yield. Through slight procedural tuning, the single-flask conversion of amides to imines, aldehydes, amines or enamines is feasible, including multicomponent syntheses.

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The mild catalytic partial reduction of amides to imines has proven to be a challenging synthetic transformation, with many transition metals directly reducing these substrates to amines. Herein, we report a mild, catalytic method for the semireduction of both secondary and tertiary amides via zirconocene hydride catalysis. Utilizing just 5 mol % of Cp2ZrCl2, the reductive deoxygenation of secondary amides is demonstrated to furnish a diverse array of imines in up to 94% yield with excel-lent chemoselectivity and without the need for glovebox handling. Moreover, a novel reductive transamination of tertiary amides is also achievable when the catalytic protocol is carried out in the presence of a primary amine at room temperature, providing access to an expanded assortment of imines. Through slight procedural modifications, the single-flask conversion of amides to imines, aldehydes, amines or enamines is feasible, including multicomponent syntheses.