Diarylated Imidazoles via Sequential Metal-Catalyzed Suzuki and C-H Activation Reactions

Significance

Reported is the synthesis of diarylated imidazoles via sequential Suzuki and Pd/Cu C-H activation reactions. Phase-transfer conditions were necessary to achieve synthetically useful results in the Suzuki reaction. Interestingly, no N-arylation products were observed. No attempt to combine the steps into a one-pot process was reported. Direct C-5 arylation of the imidazole itself was unsuccessful. The yields of each reaction are poor to reasonable and the ranges of Ar¹ and Ar² are modest with Ar² containing electron-rich and electron-poor aromatic rings. Non-aryl coupling partners were not investigated. When Ar¹ = (2-formyl-phenyl)boronic acid was used, only benzaldehyde was isolated from the reaction, undoubtedly due to protodeboronation.