Nickel-catalyzed Chemo- and Regioselective Azide–Alkyne Cycloaddition

Abstract

The metal-catalyzed cycloaddition is straightforward pathway to make functionalized heterocyclic frameworks. It has been challenging to achieve reactivity-controlled metal-catalyzed azide–alkyne cycloadditions for chemoselectivity of internal alkynes. In this paper, we describe a nickel-catalyzed [3 + 2] cycloaddition of unsymmetrical alkynes with azides that forms functionalized 1,2,3-triazoles with excellent regio- and chemoselectivity. For the clarification of the reaction mechanism, Density functional theory calculations are utilized. The computed mechanism shows that the oxidative addition of the alkyne substrate to the Ni(0)–Xantphos catalyst, followed by C–N coupling of the nickellacyclopropene intermediate, produces a nickellacyclopropene intermediate. And the consequent C–N coupling of this intermediate with an azide is responsible for the chemo- and regioselectivity.