Investigation of the catalytic activity of a Pd/biphenyl-based phosphine system in the Ullmann homocoupling of aryl bromides |
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Authors: | Shirin Nadri Ali Ataei Ezzat Rafiee |
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Institution: | a Chemistry Faculty, Razi University, Kermanshah 67149, Iran b Kermanshah Oil Refining Company, Kermanshah, Iran |
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Abstract: | We described Ullmann homocoupling promoted by a Pd/biphenyl-based phosphine system using DMF as solvent. Using Hammett equation it is found that the rate determining step of the reaction depends on the electronic nature of substituents of aryl bromides. Increase the rate of reaction with decreasing the electron donating of the substituent from NH2 to H suggesting an oxidative addition step as the rate determining step. Decrease the rate of reaction with increasing the electron-withdrawing ability of the substituent from H to NO2 indicating a reductive elimination step as the rate determining step. |
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Keywords: | C-C coupling reaction Ullmann reaction Palladium Biphenyl-based phosphine Hammett correlation |
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