Key mechanistic features of Ni-catalyzed C-H/C-O biaryl coupling of azoles and naphthalen-2-yl pivalates

Huiying Xu, Kei Muto, Junichiro Yamaguchi, Cunyuan Zhao, Kenichiro Itami*, Djamaladdin G. Musaev

*この研究の対応する著者

研究成果: Article査読

129 被引用数 (Scopus)

抄録

The mechanism of the Ni-dcype-catalyzed C-H/C-O coupling of benzoxazole and naphthalen-2-yl pivalate was studied. Special attention was devoted to the base effect in the C-O oxidative addition and C-H activation steps as well as the C-H substrate effect in the C-H activation step. No base effect in the C(aryl)-O oxidative addition to Ni-dcype was found, but the nature of the base and C-H substrate plays a crucial role in the following C-H activation. In the absence of base, the azole C-H activation initiated by the C-O oxidative addition product Ni(dcype)(Naph)(PivO), 1B, proceeds via ΔG = 34.7 kcal/mol barrier. Addition of Cs2CO3 base to the reaction mixture forms the Ni(dcype)(Naph)[PivOCs·CsCO3], 3-Cs-clus, cluster complex rather than undergoing PivO- → CsCO3- ligand exchange. Coordination of azole to the resulting 3-Cs-clus complex forms intermediate with a weak Cs-heteroatom(azole) bond, the existence of which increases acidity of the activated C-H bond and reduces C-H activation barrier. This conclusion from computation is consistent with experiments showing that the addition of Cs2CO3 to the reaction mixture of 1B and benzoxazole increases yield of C-H/C-O coupling from 32% to 67% and makes the reaction faster by 3-fold. This emerging mechanistic knowledge was validated by further exploring base and C-H substrate effects via replacing Cs2CO3 with K2CO3 and benzoxazole (1a) with 1H-benzo[d]imidazole (1b) or quinazoline (1c). We proposed the modified catalytic cycle for the Ni(cod)(dcype)-catalyzed C-H/C-O coupling of benzoxazole and naphthalen-2-yl pivalate. (Chemical Equation Presented)

本文言語English
ページ(範囲)14834-14844
ページ数11
ジャーナルJournal of the American Chemical Society
136
42
DOI
出版ステータスPublished - 2014 10月 22
外部発表はい

ASJC Scopus subject areas

  • 触媒
  • 化学 (全般)
  • 生化学
  • コロイド化学および表面化学

フィンガープリント

「Key mechanistic features of Ni-catalyzed C-H/C-O biaryl coupling of azoles and naphthalen-2-yl pivalates」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。

引用スタイル