Dehydrogenative\nCoupling\nof Alcohols with Hydrazines\nunder Nickel Catalysis

The\ndevelopment of efficient and robust catalytic systems based\non earth-abundant transition metals for fundamentally new transformations\nis crucial for sustainable chemical synthesis. Herein, an effective\nand selective Ni-catalyzed dehydrogenative coupling of alcohols with\nhydrazines with the liberation of ammonia gas is reported. Although\nseveral methods were documented for the <i>N</i>-alkylation\nreaction, the present strategy is conceptually novel, and the reaction\nproceeds through a pathway involving N–N bond cleavage of phenylhydrazine\nfollowed by hydrogen autotransfer. This unprecedented method demonstrates\na wide substrate scope, allowing for the synthesis of C–N coupled\nproducts from arylhydrazines using various types of alcohols, including\naryl, fused aryl, heteroaromatic, cyclic, and aliphatic alcohols,\nboth primary and secondary alcohols. The present catalytic approach\nwas expanded to facilitate selective deuterium incorporation reactions\nby employing deuterated alcohols at the α-methyl position of\nthe resulting <i>N</i>-alkylated products. It is noteworthy\nthat we have broadened the applicability of the current catalytic\nsystems to facilitate the ketazine synthesis of hydrazine monohydrate\nby employing secondary alcohols. The reaction utilizes an inexpensive,\nabundant, and renewable alcohol that serves as both an alkylating\nand (transfer) hydrogenating agent. Kinetic studies reveal that the\nreaction rate depends on the concentration of arylhydrazine and the\nnickel catalyst, following fractional order.