Selective Anti-Markovnikov Intramolecular Hydroamination via Photoactive Organometallic Polypyridyl Complexes

Abstract

In relatively recent years, there has been a surge of research concerning hydroamination reactions and ways to catalyze them. One of the newer classes of hydroamination catalysts is organometallic complexes that are photoactive, such as Ir(ppy)({2})(dtbpy)(PF({6})) and Ru(bpy)({3})Cl({2}). This paper focuses primarily on their viability as photocatalysts, as well as the mechanisms with which they can perform hydroamination. The tolerance and effectiveness of Ir(ppy)({2})(dtbpy)(PF({6})) were found to be exceedingly better than previous hydroamination catalysts. In an attempt to gain a better understanding of how these photocatalysts promote hydroamination, several mechanistic studies were performed. Based off of the results from Hammett analyses and KIE experiments of both photocatalysts, there is a strong indication that their hydroamination reactions can proceed through the same or different intermediates. It appears that Ru(bpy)({3})Cl({2}) can undergo an alternative hydroamination mechanism depending on the electronic nature of the substrate being catalyzed. Possibly the most important result from these studies is that the data for the alternative mechanism that Ru(bpy)({3})Cl({2}) catalyzed hydroaminations can use is consistent with a proton coupled electron transfer.