Triazine-wingtips accelerated NHC-Pd catalysed carbonylative Sonogashira cross-coupling reaction

Abstract

The transmetalation as the rate-limiting step was effectively accelerated by newly designed N-heterocyclic carbenes with triazine wingtips (T-NHC). By using a ppm-level precatalyst T-NHC-Pd (8), the highly efficient coupling of aryl iodide, alkyne and carbon monoxide furnished a variety of ynone compounds. T-NHC-Pd (5), which deprotonated 4-methyl-phenylacetylene under mild conditions, converted into alkynyl-coordinated catalytic active species PdCl(T-NHC)(Py)(alkynyl). In the putative Pd/Pd catalytic cycle, both triazine-wingtips and NHCs are key players for establishing the carbonylative cross-couplings with high TON and TOF.