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Direct C-H arylation of thiophenes at low catalyst loading of a phosphine-free bis(alkoxo)palladium complex
Yabo Li1, Jingran Wang, Mengmeng Huang
1College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University , Zhengzhou 450052, P. R. China.
Abstract:
An efficient phosphine-free direct C-H arylation of thiophenes at the α-position has been developed at low catalyst loading of bis(alkoxo)palladium complex (Cat.I, 0.1-0.2 mol %). The developed synthetic method can be applied to the synthesis of α-aryl/heteroaryl thiophenes from aryl or heteroaryl bromides in good to excellent yields and is compatible with the substrates bearing electron-donating or electron-withdrawing groups. The reactivities of the 2- and 5-positions of thiophenes are equivalent and not dependent on steric hindrance under optimal conditions. This condition can also be applied to other heterocyclic moieties such as benzothiophene, benzofuran, and pyrrole with high conversion yields.
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