DFT Study on Dinuclear Palladium Complex Catalyzed Pyrrole Formation From tert‐Butyl Isocyanide and Alkynes

Abstract

Density functional theory calculations were carried out to study the mechanisms of Pd-catalyzed reactions of alkynes with tertbutyl isocyanide forming pyrroles. In the case of di-palladium catalysis, the calculations indicated that alkyne insertion, isocyanide insertion, intramolecular cyclization, isocyanide insertion, isomerization and ligand substitution were involved in the mechanism. The intramolecular cyclization process was calculated to be the rate-determining step in the catalytic cycle. The substituent effects on the regioselectivity of reaction were also analyzed. In addition, detailed calculations on monopalladium catalysis showed that the activity of mononuclear catalysis was not as high as that of di-palladium catalysis. These calculation results were in good agreement with the experimental results.

Changes in ligand coordination mode induce bimetallic C–C coupling pathways

“…11,12 The dinuclear catalyst [PdI(P t -Bu 3 )] 2 has since been used extensively, 13 including in C–E (E = S, Se) bond formation that also follows a bimetallic mechanism. 14–16 Computational studies with other palladium complexes also support bimetallic mechanisms for pyrrole formation, 17 and alkene isomerization 18 reactions. In the context of C–C coupling catalysis, only a few examples with a postulated bimetallic mechanism are known, and little mechanistic detail has been revealed.…”