Transition-Metal-Free Base-Controlled C?N Coupling Reactions: Selective Mono Versus Diarylation of Primary Amines with 2-Chlorobenzimidazoles
Herein, a base-controlled protocol was developed for the C?N coupling of primary amines and 2-chlorobenzimidazoles, affording a handful of secondary or tertiary amines in a selective fashion. Moreover, this protocol was realized under transition-metal-fre
Sang, Wei,Gong, Yan-Yan,Cheng, Hua,Zhang, Rui,Yuan, Ye,Fan, Guang-Gao,Wang, Zhi-Qin,Chen, Cheng,Verpoort, Francis
Metal-Free Synthesis of Heteroaryl Amines or Their Hydrochlorides via an External-Base-Free and Solvent-Free C-N Coupling Protocol
Herein, a metal-free and solvent-free protocol was developed for the C-N coupling of heteroaryl halides and amines, which afforded numerous heteroaryl amines or their hydrochlorides without any external base. Further investigations elucidated that the basicity of amines and specific interactions derived from the X-ray crystallography analysis of 3j′·HCl played pivotal roles in the reactions. Moreover, this protocol was scalable to gram scales and applicable to drug molecules, which demonstrated its practical value for further applications.
Fan, Guang-Gao,Jiang, Bo-Wen,Sang, Wei,Cheng, Hua,Zhang, Rui,Yu, Bao-Yi,Yuan, Ye,Chen, Cheng,Verpoort, Francis
p. 14627 - 14639
(2021/11/01)
Mechanistic investigations and substrate scope evaluation of ruthenium-catalyzed direct sp3 arylation of benzylic positions directed by 3-substituted pyridines
A highly efficient direct arylation process of benzylic amines with arylboronates was developed that employs Ru catalysis. The arylation takes place with greatest efficiency at the benzylic sp3 carbon. If the distance to the activating aryl ring is increased, arylation is still possible but the yield drops significantly. Efficiency of the CH activation was found to be significantly increased by use of 3-substituted pyridines as directing groups, which can be removed after the transformation in high yield. Calculation of the energy profile of different rotamers of the substrate revealed that presence of a substituent in the 3-position favors a conformation with the CH2 group adopting a position in closer proximity to the directing group and facilitating C-H insertion. This operationally simple reaction can be carried out in argon atmosphere as well as in air and under neutral reaction conditions, displaying a remarkable functional group tolerance. Mechanistic studies were carried out and critically compared to mechanistic reports of related transformations.
Dastbaravardeh, Navid,Kirchner, Karl,Schnuerch, Michael,Mihovilovic, Marko D.
p. 658 - 672
(2013/02/26)
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