CP-2569

Transition-metal hydrides stand as indispensable intermediates in both energy conversion and organic synthesis. Their electrochemical generation represents a compelling sustainable approach, enabling precise control over the reactivity and expanding the scope of electrocatalytic hydrogenation and isomerization. However, a major challenge in Ni-catalyzed electrochemical hydrogenation is the competing hydrogen evolution reaction (HER), which has led to various innovative strategies aimed at circumventing Ni-H formation. Here, we pursued an alternative approach by designing a bifunctional ligand with a pendant amine moiety to promote Ni-H formation. This design enabled selective (semi)hydrogenation of a diverse range of substrates, including terminal and internal alkynes, alkenes, and aldehydes, achieving an unprecedented substrate scope. Remarkably, we also demonstrated tunable positional selectivity for olefin isomerization by employing different types of proton sources. Our hydrogenation and isomerization method also exhibits excellent functional group tolerance, streamlining access to pharmaceuticals and their derivatives. Computational studies revealed the crucial, noninnocent role of the proton source in modulating metal hydride selectivity, either through hydrogen bonding, direct protonation of the pendant amine, or facilitation of protodemetalation.

Aromatic allylamines are essential in the synthesis of diverse pharmaceutical building blocks. While oxidative allylic C─H amination using anilines has advanced significantly, achieving intermolecular reductive allylic C─H amination of olefins with readily available nitroarenes remains a considerable challenge. Here, we demonstrate that replacing silanes with a combination of protons and electrons enables selective reductive allylic C─H amination, avoiding the competing hydroamination pathway. The key to this transformation is the use of 2,2,2‐trifluoroethanol (TFE) as the solvent. This process complements previous oxidative allylic C─H amination by eliminating the need for noble metal catalysts while tolerating oxidizable or nucleophilic functional groups. Notably, this method facilitates the functionalization of bioactive compounds, underscoring its potential in medicinal chemistry. Furthermore, by leveraging its reactivity with trisubstituted olefins, this approach, when combined with metal hydride atom transfer (MHAT) reactions, offers a unique strategy for regioselective and modular difunctionalization of aliphatic olefins. Experimental and computational mechanistic studies highlight the crucial roles of TFE in stabilizing the nitrosoarene intermediate and promoting the key nitroso‐ene step.