Mechanistic Investigations and Substrate Scope Evaluation of Ruthenium-Catalyzed Direct sp3 Arylation of Benzylic Positions Directed by 3-Substituted Pyridines

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• 作者：Navid Dastbaravardeh ; Karl Kirchner ; Michael Schn眉rch ; Marko D. Mihovilovic
• 刊名：The Journal of Organic Chemistry
• 出版年：2013
• 出版时间：January 18, 2013
• 年：2013
• 卷：78
• 期：2
• 页码：658-672
• 全文大小：578K
• 年卷期：v.78,no.2(January 18, 2013)
• ISSN：1520-6904

文摘

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鈥揌 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.