On the mechanism of acceptorless dehydrogenation of N-heterocycles catalyzed by BuOK: a computational study.

The catalytic acceptorless dehydrogenation (ADH) of saturated N-heterocycles has recently gained considerable attention as a promising strategy for hydrogen release from liquid organic hydrogen carriers (LOHCs). Recently, a simple BuOK base-promoted ADH of N-heterocycles was developed by Yu ( 2019, , 3958). However, it is still open as to how the BuOK plays a catalytic role in the ADH process. Herein, our density functional study reveals that the BuOK catalyzes the ADH of 1,2,3,4-tetrahydroquinoline (THQ) through a quasi-metal-ligand bifunctional catalytic channel or a base-catalyzed pathway with close energy barriers. The hydride transfer in the first dehydrogenation process is determined to be the rate determining step, and the second dehydrogenation can proceed directly from 34DHQ regulated by the BuOK. In addition, the computational results show that the cooperation of a suitable alkali metal ion with the BuO group is so critical that the BuOLi and the isolated BuO are both inferior to BuOK as a dehydrogenation catalyst.