Computational Mechanistic Study of Redox-Neutral Rh(III)-Catalyzed C-H Activation Reactions of Arylnitrones with Alkynes: Role of Noncovalent Interactions in Controlling Selectivity

Yang-Yang Xing; Jian-Biao Liu; Ying-Ying Tian; Chuan-Zhi Sun; Fang Huang; De-Zhan Chen

doi:10.1021/acs.jpca.6b10367

Computational Mechanistic Study of Redox-Neutral Rh(III)-Catalyzed C-H Activation Reactions of Arylnitrones with Alkynes: Role of Noncovalent Interactions in Controlling Selectivity

J Phys Chem A. 2016 Nov 23;120(46):9151-9158. doi: 10.1021/acs.jpca.6b10367. Epub 2016 Nov 14.

Authors

Yang-Yang Xing¹, Jian-Biao Liu¹, Ying-Ying Tian¹, Chuan-Zhi Sun¹, Fang Huang¹, De-Zhan Chen¹

Affiliation

¹ College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Shandong Normal University , Jinan 250014, P. R. China.

PMID: 27802050
DOI: 10.1021/acs.jpca.6b10367

Abstract

The mechanism of redox-neutral Rh(III)-catalyzed coupling reactions of arylnitrones with alkynes was investigated by density functional theory (DFT) calculations. The free energy profiles associated with the catalytic cycle, involving C(sp²)-H activation, insertion of alkyne, transfer of O atom, cyclization and protodemetalation, are presented and analyzed. An overwhelming preference for alkyne insertion into Rh-C over Rh-O is observed among all pathways, and the most favorable route is determined. The pivalate-assisted C-H activation step is turnover-limiting, and the cyclization step determines the diastereoselectivity of the reaction, with the stereoselectivity arising mainly from the difference of noncovalent interactions in key transition states. The detailed mechanism of O atom transfer, Rh^III-Rh^I-Rh^III versus Rh^III-Rh^V-Rh^III cycle, is discussed.