Palladium-catalyzed Cadiot-Chodkiewicz

Pd/Cu-catalyzed cross-coupling of organohalides with terminal alkynes. Cf. Cadiot-Chodkiewicz coupling and Castro-Stephens reaction. The Castro-Stephens coupling uses stoichiometric copper, whereas the Sonogashira variant uses catalytic palladium and copper. 

Although palladium-catalyzed processes have also achieved improvements in the field of acetylenic coupling [2], the Glaser-Hay and Cadiot-Chodkiewicz copper-mediated methods still remain the most used. Further mechanistic investigations seem to be necessary, to overcome the limitations of the existing procedures, mainly poor selectivity and predictability. 

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