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Mechanism Selection for Regiocontrol in Base‐Assisted, Palladium‐Catalysed Direct CH Coupling with Halides: First Approach for Oxazole‐ and Thiazole‐4‐Carboxylates
Author(s) -
Théveau Laure,
Verrier Cécile,
Lassalas Pierrik,
Martin Thibaut,
Dupas Georges,
Querolle Olivier,
Van Hijfte Luc,
Marsais Francis,
Hoarau Christophe
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201101615
Subject(s) - thiazole , oxazole , chemistry , steric effects , deprotonation , palladium , carboxylate , combinatorial chemistry , halide , stereochemistry , decarboxylation , medicinal chemistry , catalysis , photochemistry , organic chemistry , ion
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 series were then designed by controlling the balance between electronic and steric factors. Notably, charge interactions between the palladium catalyst and substrate were identified as a parameter for controlling selectivity and reducing the impact of steric factors in the CMD reaction.