Experimental and mechanistic insights into copper(ii)–dioxygen catalyzed oxidative N-dealkylation of N-(2-pyridylmethyl)phenylamine and its derivatives

Abstract

A di-(2-pyridylmethyl)phenylamine ((PyCH₂)₂NPh) supported Cu(II)/O₂ catalytic system was explored with the synthesis of pyridylmethyl-based compounds of carboxylate (PyCOOH), amide (PyC(O)NHPh), and imine (PyCHNPh) from the oxidative N-dealkylation of N-(2-pyridylmethyl)phenylamine (PyCH₂NHPh) and its derivatives, by means of controlling the addition of a base and/or water to the reaction system under a dioxygen atmosphere at room temperature. Experimental studies showed that the imine and amide species could be precursors in succession in the way to the final oxidation state of carboxylates. A cyclic catalytic mechanism was proposed including the base triggered C–H bond activation of the 2-pyridylmethyl group (PyCH₂–) and the intermolecular Cu–OOH α-hydrogen atom abstraction from the coordinated imine substrate (PyCHNPh).