Theoretical Probe to the Mechanism of Pt-catalyzed C-H Acylation Reaction: Possible Pathways for the Key Acylation Reaction of Platinacycles

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Elizabeth F Warden (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Transition metal-catalyzed C-H bond functionalization offers a variety of desirable transformations of simple hydrocarbons to more complex compounds with applications being applied in pharmaceuticals to material sciences. In 2017 , Dr. Huo's research group reported a unique Pt-catalyzed acylation of 2-aryloxypyridines through direct CH activation. The significance of this reported reaction is represented in the experiment occurring without any oxidants or additives; furthermore , presenting this relatively straight forward reaction mechanism which is initiated only in the presents of platinum. However , through computational analysis the key acylation step of the cyclometalated platinum complex has shown quite intriguing results. Utilization of the nudged elastic band (NEB) method followed by a min-mode optimization of the potential transition states has shown preference towards a nucleophilic substitution over the previously proposed electrophilic addition during the key acylation step. Theoretically , this DFT study at M062X/6-311g**/def2-TZVP-Pt level of theory was unable to simulate the initial formal electrophilic substitution reaction proposed as the arenium ion C could not be minimized. Therefore based on current results the preferred pathway is as follows: (1) nucleophilic substitution of the acyl chloride to form five-coordinate acylplatinum complex with a barrier of 21.7083 k cal/mol (B) , followed by (2) 1 , 2-migration of the acyl group from the platinum to the metalated carbon to form a Pt-arene 2-complex or platinacyclopropane with a barrier of 15.0713 kcal/mol (E). Lastly , (3) Re-aromatization of E leads to the acylated product P with a barrier of 35.3138 kcal/mol. Further probing and key mechanistic results will be presented.

Additional Information

Publication

Thesis

Language: English

Date: 2019

Keywords

Computational Chemistry, NEB, Theoretical Study, Platinum Catalyst, Nudged Elastic Band Method, Dimer, Transition State localization, QST2, Gaussian, C-H Activation, C-H Funtionalization

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