Zinc – catalyzed reduction of N – heterocycles

Abstract

Novel bidentate amine – imine, and amido – imine ligands were synthesized. The former species was reacted with ZnMe2 to generate zinc methyl complex. The compound was fully characterized by 1H NMR and X – ray spectroscopy. The zinc methyl complex demonstrated rather limited catalytic activity in hydroboration and hydrosilylation of N – heterocycles. Consequently, a new zinc hydride complex was synthesized using an amido – imine ligand as a precursor. A series of nitrogen heteroaromatics were successfully hydroborated using catalytic amounts of zinc hydride species. Deuterium – labeling experiments, and kinetic studies allowed to get insights into the reaction mechanism. It was proposed that the hydride transfer proceeds via a six – membered transition state orchestrated by the Lewis acidic zinc – hydride complex. Another project was focused on the synthesis of a potentially redox “non – innocent” diimine ligand, using Arduengo’s diketone as the starting point. Attempts to install an imine moiety resulted in a surprising reaction outcome.