Mechanistic Investigations and Substrate Scope Evaluation of Ruthenium-Catalyzed Direct sp3 Arylation of Benzylic Positions Directed by 3-Substituted Pyridines
摘要:
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 sp(3) 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.
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
在此,开发了一种无金属和无溶剂的方案,用于杂芳基卤化物和胺的 C-N 偶联,在没有任何外部碱的情况下提供了许多杂芳基胺或其盐酸盐。进一步的研究表明,胺的碱性和源自3j'·HCl的 X 射线晶体学分析的特定相互作用在反应中起关键作用。此外,该协议可扩展到克级并适用于药物分子,这证明了其进一步应用的实用价值。
Transition‐Metal‐Free Base‐Controlled C−N Coupling Reactions: Selective Mono<i>Versus</i>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‐free conditions, and the variation of the base from iPr2NH to LiOtBu completely switched the selectivity from monoarylation to diarylation. Further investigations
本文中,开发了一种碱控制的方案,用于伯胺和2-氯苯并咪唑的C-N偶联,以选择性方式提供了少量仲胺或叔胺。此外,该方案是在无过渡金属条件下实现的,碱从i Pr 2 NH到LiO t Bu的变化完全将选择性从单芳基化转变为二芳基化。进一步的研究表明,所用碱的种类,内在的碱性和数量极大地影响了这些反应。
SIMONOV A. M.; KOMISSAROV V. N., XIMIYA GETEROTSIKL. SOEDIN. <KGSS-AQ>, 1975, HO 6, 826-828