We have used density functional theory to explore the copper(I)-catalyzed reaction between a mesyl azide and a terminal alkyne that leads to a ketenimine whose interaction with nucleophilic water produces an amide. It is well reported in the literature that a cuprated triazole intermediate is formed during the course of such a catalytic cycle. In this contribution, we investigated the stability of this key intermediate by varying the R substituent on the azide and found that electron-withdrawing R substituents make this intermediate more reactive toward ring opening/ N 2 elimination; an electron-withdrawing R substituent facilitates this process by weakening the N−N bond being cleaved. We also rationalized why the cycloaddition step in this class of click reactions is required to proceed via a binuclear mechanism. The copper(I) acetylide intermediate formed during the catalysis gains extra stability upon scavenging a second Cu complex, resulting in the cycloaddition step occurring with a lower activation barrier. We also noticed that, similar to the ring closure step, inclusion of a second Cu complex may accelerate the ring opening/N 2 elimination process. It was shown that the ketenimine needs to coordinate to a copper center via its nitrogen atom in order to be activated toward hydrolysis.

Density functional theory (DFT) at the M06 level was utilized to compare the reactivity of Pd(P t Bu 3 ) 2 with that of Pd 2 (dba) 3 in catalyzing carbostannylation of alkynes in the presence of [AuL] + , where L is a phosphine ligand. In both cases, a common active catalyst is found to be responsible for conducting the reaction. The underlying reason for this is that [AuL] + is capable of acting as a phosphine scavenger and removing both phosphines from Pd(P t Bu 3 ) 2 . The phosphine scavenger property of the cationic gold complexes may find applications in other catalytic coupling reactions. We also found that other Lewis acids such as AuCl, CuCl, and ZnCl 2 might have potential for use as phosphine scavengers from palladium(0) bis(phosphine) complexes.

A dichotomy in carbon versus bromide reductive elimination in CuIII–NHC complexes is rationalized by computational methods (DFT).