N-Heterocyclic carbene/palladium synergistic catalysis in organic synthesis.

The cooperation of two distinct catalytic cycles to activate different reactive centers leading to a chemical transformation has been classified as synergistic catalysis. The synergistic combination of NHC with palladium catalysis has emerged as a powerful strategy in the last few years. Merging the ability of NHCs to inverse the polarity of a functional group with the unique reactivity of palladium enables transformations that cannot be accomplished by either of these catalysts alone.

Pd/Brønsted acid catalysed intramolecular -allylation of indoles and pyrroles with alkynes for the synthesis of N-fused heterocycles.

We, herein, report a Pd(0) and Brønsted acid-catalyzed redox-neutral intramolecular -allylation of indoles and pyrroles with alkynes for the synthesis of biologically important imidazolidinone-fused N-heterocycles. The allylation is completely atom-economical and is applicable to a wide range of substrates. The methodology eliminates the use of a leaving group or an oxidizing agent, often employed for the allylation of nucleophiles.