Details

Autor(en) / Beteiligte

• Kim, Daeun
• Choi, Geunho
• Kim, Weonjeong
• Kim, Dongwook
• Kang, Youn K
• Hong, Soon Hyeok

Titel

The site-selectivity and mechanism of Pd-catalyzed C(sp)-H arylation of simple arenes

Ist Teil von

• Chemical science (Cambridge), 2021-01, Vol.12 (1), p.363-373

Ort / Verlag

Cambridge: Royal Society of Chemistry

Erscheinungsjahr

2021

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• Control over site-selectivity is a critical challenge for practical application of catalytic C-H functionalization reactions in organic synthesis. Despite the seminal breakthrough of the Pd-catalyzed C(sp 2 )-H arylation of simple arenes via a concerted metalation-deprotonation (CMD) pathway in 2006, understanding the site-selectivity of the reaction still remains elusive. Here, we have comprehensively investigated the scope, site-selectivity, and mechanism of the Pd-catalyzed direct C-H arylation reaction of simple arenes. Counterintuitively, electron-rich arenes preferably undergo meta -arylation without the need for a specifically designed directing group, whereas electron-deficient arenes bearing fluoro or cyano groups exhibit high ortho -selectivity and electron-deficient arenes bearing bulky electron-withdrawing groups favor the meta -product. Comprehensive mechanistic investigations through a combination of kinetic measurements and stoichiometric experiments using arylpalladium complexes have revealed that the Pd-based catalytic system works via a cooperative bimetallic mechanism, not the originally proposed monometallic CMD mechanism, regardless of the presence of a strongly coordinating L-type ligand. Notably, the transmetalation step, which is influenced by a potassium cation, is suggested as the selectivity-determining step. The transmetalation step, not the C-H activation step, is suggested as the selectivity-determining step in Pd-catalyzed C-H arylation of simple arenes.