Chemoselective Catalytic Dehydrogenative Cross-Coupling of 2-Acylimidazoles: Mechanistic Investigations and Synthetic Scope

Tsukushi Tanaka, Kayoko Hashiguchi, Takafumi Tanaka, Ryo Yazaki, Takashi Ohshima

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Chemoselective iron-catalyzed dehydrogenative cross-coupling using 2-acylimidazoles is described. The addition of a phosphine oxide ligand substantially facilitated the generation of tert-butoxy radicals from di-tert-butyl peroxide, allowing for efficient benzylic C-H bond cleavage under mild conditions. Extensive mechanistic studies revealed that the enolization of 2-acylimidazole proceeded through dual iron catalyst activation, followed by subsequent chemoselective cross-coupling with a benzyl radical over an undesired benzyl radical-derived homocoupling dimer that inevitably formed in earlier reported conditions. A variety of alkylarenes, aliphatic alkane, and functionalized 2-acylimidazoles were applicable, demonstrating the synthetic utility of the present catalysis. Contiguous all-carbon quaternary carbons were constructed through dehydrogenative cross-coupling. The catalytic chemoselective activation of 2-acylimidazole over bidentate coordinative and much more acidic malonate diester was particular noteworthy. Catalytic oxidative cross-enolate coupling of two distinct carboxylic acid equivalents was also achieved using acetonitrile as a coupling partner.

Original languageEnglish
Pages (from-to)8430-8440
Number of pages11
JournalACS Catalysis
Volume8
Issue number9
DOIs
Publication statusPublished - Sep 7 2018

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

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