A manganese catalyst for highly reactive yet chemoselective intramolecular C(sp3)–H amination

 Shauna M. Paradine, Jennifer R. Griffin, Jinpeng Zhao, Aaron L. Petronico, Shannon M. Miller, & M. Christina White

 

Nature Chemistry 7,  987–994  (2015)  doi:10.1038/nchem.2366  Received 01 July 2015             Accepted 01 September 2015    Published online 05 October 2015      

 

Abstract

C–H bond oxidation reactions underscore the existing paradigm wherein high reactivity and high selectivity are inversely correlated. The development of catalysts capable of oxidizing strong aliphatic C(sp³)–H bonds while displaying chemoselectivity (that is, tolerance of more oxidizable functionality) remains an unsolved problem. Here, we describe a catalyst, manganese tert-butylphthalocyanine [Mn(^tBuPc)], that is an outlier to the reactivity–selectivity paradigm. It is unique in its capacity to functionalize all types of C(sp³)–H bond intramolecularly, while displaying excellent chemoselectivity in the presence of π functionality. Mechanistic studies indicate that [Mn(^tBuPc)] transfers bound nitrenes to C(sp³)–H bonds via a pathway that lies between concerted C–H insertion, observed with reactive noble metals such as rhodium, and stepwise radical C–H abstraction/rebound, as observed with chemoselective base metals such as iron. Rather than achieving a blending of effects, [Mn(^tBuPc)] aminates even 1° aliphatic and propargylic C–H bonds, demonstrating reactivity and selectivity unusual for previously known catalysts.

 

http://www.nature.com/nchem/journal/v7/n12/full/nchem.2366.html