Direct Imidation to Construct 1H-Benzo[d]imidazole through PdII-Catalyzed CH Activation Promoted by Thiourea

✍ Scribed by Qing Xiao; Wen-Hua Wang; Gang Liu; Fan-Ke Meng; Jia-Hua Chen; Zhen Yang; Zhang-Jie Shi

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 312 KB
• Volume: 15
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200900154

✦ Synopsis

A novel and straightforward method to construct 1H-benzo [d]imidazole was developed b means of Pd II -catalyzed intramolecular CÀH activation starting from readily available N-phenylbenzimidamide. The detailed mechanism studies indicated that a palladacycle monomer or dimer is the key intermediate for this transformation and thiourea was first used to prompt the efficiency of C À H activation.

Much attention has been paid to C À N formation in the past two decades. Many useful methods have been developed to construct CÀN bonds through transition-metal-catalyzed amination/amidation from aryl halides. [1] Very recently, new methods have been developed to construct CÀN bonds intra/intermolecularly through direct aromatic C À H functionalization. Among these investigations, Buchwald and co-workers pioneered studies to construct a carbazole core structure through Pd II -catalyzed intramolecular C À H activation. [2] Shortly afterwards, Che, Yu, and co-workers reported the intermolecular CÀN formation through Pd II -or Cu II -catalyzed CÀH functionalization, respectively. [3] When we were preparing this manuscript, Buchwald and co-workers reported a novel Cu-catalyzed direct C À H functionalization to produce benzimidazoles similar to our design. In their report, steric hindered benzimidamides showed the excellent reactivities to facilitate this transformation. [4] Herein we report a new method to construct 1H-benzo[d]imidazole through Pd II -catalyzed intramolecular CÀN formation, in [a] Q.