A radical C–H arylation reaction of oxazoles with (hetero)aryl iodides using Cs2CO3 as base/electron donor and 1,1′-bis(diphenylphosphino) ferrocene (dppf) as a catalytic SET mediator is reported. The overall reaction likely follows the general base-promoted homolytic aromaticsubstitution mechanism through a radical-chain pathway. DFT calculations suggest that dppf forms a complex with CsCO3–, enhancing
报道了使用Cs 2 CO 3作为碱/电子给体和1,1'-双(二苯基膦基)二茂铁(dppf)作为催化SET介体,恶唑与(杂)芳基碘化物的自由基CH芳基化反应。整个反应可能通过自由基链途径遵循一般的碱促进的均质芳族取代机理。DFT计算表明,dppf与CsCO 3 –形成络合物,增强了SET还原能力,可从ArI生成芳基。
Palladium-Catalyzed Direct (Hetero)arylation of Ethyl Oxazole-4-carboxylate: An Efficient Access to (Hetero)aryloxazoles
toward 2-(hetero)arylated and 2,5-di(hetero)arylated oxazoles through regiocontrolledpalladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate with iodo-, bromo-, and chloro(hetero)aromatics followed by a two-step hydrolysis/decarboxylation sequence was described. The method was applied here to a neat synthesis of two 2,5-di(hetero)aryloxazole natural products, balsoxin and texaline
Carbonates: eco-friendly solvents for palladium-catalysed direct arylation of heteroaromatics
作者:Jia Jia Dong、Julien Roger、Cécile Verrier、Thibaut Martin、Ronan Le Goff、Christophe Hoarau、Henri Doucet
DOI:10.1039/c0gc00229a
日期:——
The palladium-catalyseddirect2-, 4- or 5-arylation of a wide range of heteroaromatics with aryl halides proceed in moderate to good yields using the eco-friendly solvents carbonates. The best yields were obtained using benzoxazole or thiazole derivatives. The arylation of furan, thiophene, pyrrole, imidazole or isoxazole derivatives was found to require a more elevated reaction temperature.
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
Indole derivatives that are useful for treating pain, inflammation and other conditions are described. Certain of the compounds are benzyl derivatives and others are benzoyl derivatives. The compounds are substituted at least at the 3 position of the indole.