Mechanism of Coupling of Alcohols and Amines to Generate Aldimines and H ₂ by a Pincer Manganese Catalyst

Acceptorless dehydrogenative coupling (ADC) of alcohols and amines using a manganese-based catalyst is able to produce aldimines, which have a wide reactivity, without underestimating the generation of a clean fuel, since as a result of this coupling, molecular hydrogen is also obtained. Therefore, the aldimine synthesis represents an interesting reaction from chemical and clean energy points of view. In this work, the computational study, via density functional theory (DFT) calculations, of a manganese-based catalyst for the acceptorless dehydrogenative coupling of alcohols and amines, together with the elucidation of its catalytic cycle using benzene as a solvent, is carried out. Calculations provided insight not only into the catalytic pathway but also into the noncatalyzed organic transformation to reach the desired aldimine, on the basis of the aldehyde generated in the catalytic cycle. The importance of the alternative isomers of the Mn-pincer complex, previously characterized experimentally, and the assisting role of alcohol or water are also described.