Synthesis of Di-Substituted Alkynes via Palladium-Catalyzed Decarboxylative Coupling and C-H Activation

A straightforward methodology for the decarboxylative cross-coupling of aryl bromides and phenylpropiolic acid using a Pd(II)-NHC catalyst has been developed. Various aryl bromides have been successfully transformed into the corresponding di-substituted alkynes using environmentally benign conditions (weak base and ethanol as solvent). This efficient catalytic system also proved useful for the copper-free Sonogashira coupling of aryl and alkenyl bromides with various terminal alkynes. The synthetic utility of these methodologies was highlighted in the synthesis of a polyaromatic compound and various fluoroenynes.