Mechanism Selection for Regiocontrol in Base-Assisted, Palladium-Catalysed Direct CH Coupling with Halides: First Approach for Oxazole- and Thiazole-4-Carboxylates
Both base‐assisted non‐concerted metallation–deprotonation (nCMD) and concerted metallation–deprotonation (CMD) have been identified as two potent operating mechanisms in palladium‐catalysed direct CH coupling of oxazole and thiazole‐4‐carboxylate esters with halides through base‐ and solvent‐effect experiments. Novel C2‐ and C5‐selective CMD direct arylation procedures in oxazole‐ and thiazole‐4‐carboxylate