POP-Pincer Xantphos Pd Complex of 4-Pyridylthiolate: Cyclocarbonylative Reaction for the Synthesis of Flavones Using Cobalt Carbonyl as a C1 Source

The mononuclear cationic palladium complex of 4-pyridylthiolate and Xantphos having k3 POP-coordinate mode was synthesized and used as a catalyst for the cyclocarbonylative synthesis of oxygen-containing heterocyclic flavones. The synthesized Pd complex was characterised by elemental analysis, 1H, 13C{1H} and 31P{1H} NMR spectroscopy, and single crystal X-ray diffraction analysis. Cyclocarbonylative synthesis was achieved by using Co2(CO)8 as a solid CO surrogate as it is inexpensive, less toxic, low melting solid. The synthetic utility of the protocols explored to the various functional group on terminal alkynes to yield corresponding flavones. The palladium complex is a stable, air and moisture insensitive catalyst and remains active with low loading for the synthesis of flavone as a major product.