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Ruthenium-Carbonyl-Catalyzed Reaction of Pyridylbenzenes with CO and Olefins. Carbonylation at a C-H Bond
Naoto Chatani, Yutaka Ie, Takahide Fukuyama, Fumitoshi Kakiuchi, and Shinji Murai
Department of Applied Chemistry, Faculty of Engineering, Osaka University,
Suita, Osaka 565, Japan
A ruthenium-carbonyl-catalyzed carbonylation at a C-H bond in a benzene ring will be presented. The reaction of pyridylbenzenes with CO (20 atm) and ethylene in toluene at 160 deg.C in the presence of a catalytic amount of Ru3(CO)12 resulted in propionylation at an ortho C-H bond in the benzene ring. Carbonylation did not occur at the pyridine ring, although this is necessary as a directing group to promote the reaction. Olefins such as trimethylvinylsilane and t-butylethylene in place of ethylene could also be used in this reaction, however 1-hexene, cyclohexene, allyltrimethylsilane, styrene, methyl methacrylate, vinyl acetate, triethoxyvinylsilane, and isopropenyltrimethylsilane did not afford the coupling products. In the reaction of meta-substituted pyridylbenzenes, such as those having Me, CF3, OMe, and COOMe group, carbonylation took place at the less hindered C-H bond exclusively, irrespective of the electronic nature of the substituents. It is apparent that steric factors are more important for the control of regioselectivity. The present reaction represents the first, effective catalytic carbonylation reaction involving cleavage of the benzene C-H bond.
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