Palladium catalyzed reductive homocoupling reactions of aromatic halides in dimethyl sulfoxide (DMSO) solution

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• 作者：Chenze Qi ; Xudong Sun ; Cuiyun Lu ; Jinzhi Yang ; Yijun Du ; Huajiang Wu ; Xian-Man Zhang
• 关键词：Palladium catalyst ; Homocoupling ; Aromatic halides ; Alkali fluoride bases ; X-ray photoelectron spectroscopy ; Reaction mechanism
• 刊名：Journal of Organometallic Chemistry
• 出版年：2009
• 出版时间：15 August 2009
• 年：2009
• 卷：694
• 期：18
• 页码：2912-2916
• 全文大小：258 K

文摘

Biaryls were obtained in good to excellent yields from the palladium catalyzed reductive homocoupling reactions of various aryl iodides and bromides in dimethyl sulfoxide (DMSO) solution without the need for any additional reducing reagents. Pd(dppf)Cl₂ is the most effective among the screened palladium catalysts for the homocoupling reactions. Fluorides, carbonates, acetates and hydroxides can be used as bases at promoting the palladium catalyzed reductive homocoupling of aryl halides in DMSO solution. X-ray photoelectron spectroscopic (XPS) analysis shows that the oxidative Pd²⁺(dppf) species can be reduced into the Pd⁰(dppf) active species by solvent DMSO molecules to furnish the catalytic cycle, indicating that DMSO plays a dual role as both solvent and reducing reagent. A plausible reaction mechanism has been discussed. Elimination of additional reducing reagents will not only reduce the reaction operation cost, but will also simplify the product separation and purification.