Tandem Transformation of Nitro Compounds into N-Methylated Amines: Greener Strategy for the Utilization of Methanol as a Methylating Agent

A simple air- and moisture-stable, highly efficient ruthenium NNN pincer complex is reported for the first time to catalyze the tandem transformation of various aromatic and aliphatic nitro compounds into the corresponding N-methylated amines in up to 98 % yield by using methanol as a green methylating agent. Gram-scale reactions of challenging nitro substrates demonstrated the practical application aspects of this catalytic system. Importantly, the N-methylamine moiety could be smoothly introduced to various complex molecular structures without using any expensive palladium/phosphine/amine-based cross-coupling reactions.

Cobalt-Catalyzed Alkylation of Secondary Alcohols with Primary Alcohols via Borrowing Hydrogen/Hydrogen Autotransfer

Alcohols are promising sustainable starting materials because they can be obtained from abundant and indigestible biomass. The substitution of expensive noble metals in catalysis by earth abundant 3d metals, such as Mn, Fe, or Co, (nonprecious or base metals) is a related key concept with respect to sustainability. Here, we report on the first cobalt-catalyzed alkylation of secondary alcohols with primary alcohols. Easy-to-synthesize and easy-to-activate PN₅ P-pincer-ligand-stabilized Co complexes developed in our laboratory mediate the reaction most efficiently. The catalysis is applicable to a broad substrate scope and proceeds under relatively mild conditions. We have even demonstrated the coupling of a variety of purely aliphatic alcohols with a base or nonprecious metal catalyst. Mechanistic studies indicate that the reaction follows the borrowing hydrogen or hydrogen autotransfer concept.