Direct C - H arene homocoupling over gold nanoparticles supported on metal oxides

Tamao Ishida, Shohei Aikawa, Yoshiyuki Mise, Ryota Akebi, Akiyuki Hamasaki, Tetsuo Honma, Hironori Ohashi, Tetsuro Tsuji, Yasushi Yamamoto, Mitsuru Miyasaka, Takushi Yokoyama, Makoxto Tokunaga

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The direct C - H/C - H bond coupling of dimethyl phthalate was performed successfully over supported gold nanoparticle catalysts. Gold on reducible metal oxides, such as Co3O4, and on inert oxides that have an oxygen-releasing capacity, such as ZrO2, showed the highest catalytic activity for the production of biphenyl tetracarboxylate using O2 as the sole oxidant. Supported Pd(OH)2 also catalyzed the reaction, but the catalytic activity was inferior to that of gold. Moreover, the gold catalysts exhibited excellent regioselectivity for the synthesis of valuable 3,3′,4,4′-tetrasubstituted biphenyls by coupling with each other at the 4-position without the need for additional ligands. Gold catalysts also promoted the oxidative homocoupling of arenes including o-xylene to give symmetrical biaryls with high regioselectivity. X-ray absorption fine structure measurements revealed that the catalytically active species was Au0 and that the lattice oxygen of Co3O4 played an important role in the gold-catalyzed oxidative coupling. The results of the kinetic studies were consistent with an electrophilic aromatic substitution pathway. Regioselectivity is not controlled by directing groups or the electronic character of the substituents but by steric hindrance, which suggests that gold nanoparticles not only catalyze the oxidative coupling but also act as bulky ligands to control the regioselectivity.

Original languageEnglish
Pages (from-to)695-701
Number of pages7
JournalChemSusChem
Volume8
Issue number4
DOIs
Publication statusPublished - Feb 2015

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All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Chemical Engineering(all)
  • Materials Science(all)
  • Energy(all)

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