Density functional theory investigation on Pd-catalyzed cross-coupling of azoles with aryl thioethers

作者：Yang, Yi-Meng; Dang, Zhi-Min; Yu, Hai-Zhu^*

来源：Organic and Biomolecular Chemistry, 2016, 14(19): 4499-4506.

DOI：10.1039/c6ob00607h

• C-H ARYLATION
• BOND ARYLATION
• MECHANISTIC INSIGHTS
• TRANSITION-METALS
• AB-INITIO
• ACTIVATION
• NI
• HETEROARENES
• DERIVATIVES
• SCOPE

In the present study, a density functional theory (DFT) study has been carried out on the Pd-catalyzed coupling of azoles with aryl thioethers. Our effort is mainly put into identifying the most feasible catalytic cycle, and especially the origin of chemoselectivity for the exclusive aromatic C-sp2-S bond activation (in the presence of an alkyl C-sp3-S bond). The coupling mainly consists of three steps: C-S activation, (NaOBu)-Bu-t mediated C-H palladation, and reductive elimination. The C-sp2-S activation is favored over C-sp3-S activation, and thus di(hetero)aryls are the predicted products. This conclusion well reproduces Wang's recent experimental observations. The rate-and chemoselectivity determining steps of the C-H/C-sp2-S activation mechanism are C-H palladation and C-S activation steps, respectively. Analyzing the origin of chemoselectivity, we found that the easiness of Pd catalyzed C-S activation is independent of the C-S bond strengths in thioether substrates. By contrast, d-pi* backdonation in C-sp2-S-Pd intermediates is the main driving force for the favorable C-sp2-S activation (over the C-sp3-S activation).

• 出版日期2016
• 单位北京科技大学; 安徽大学