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Direct CH Arene Homocoupling over Gold Nanoparticles Supported on Metal Oxides
Author(s) -
Ishida Tamao,
Aikawa Shohei,
Mise Yoshiyuki,
Akebi Ryota,
Hamasaki Akiyuki,
Honma Tetsuo,
Ohashi Hironori,
Tsuji Tetsuro,
Yamamoto Yasushi,
Miyasaka Mitsuru,
Yokoyama Takushi,
Tokunaga Makoto
Publication year - 2015
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201402822
Subject(s) - regioselectivity , chemistry , catalysis , steric effects , photochemistry , oxidative addition , colloidal gold , oxidative coupling of methane , reactivity (psychology) , metal , biphenyl , combinatorial chemistry , nanoparticle , medicinal chemistry , organic chemistry , materials science , nanotechnology , medicine , alternative medicine , pathology
The direct CH/CH bond coupling of dimethyl phthalate was performed successfully over supported gold nanoparticle catalysts. Gold on reducible metal oxides, such as Co 3 O 4 , and on inert oxides that have an oxygen‐releasing capacity, such as ZrO 2 , showed the highest catalytic activity for the production of biphenyl tetracarboxylate using O 2 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 Au 0 and that the lattice oxygen of Co 3 O 4 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.