Synthesis of benzylpalladium complexes through C-O bond cleavage of benzylic carboxylates: Development of a novel palladium-catalyzed benzylation of olefins |
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Authors: | Hirohisa Narahashi Akio Yamamoto |
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Institution: | Department of Applied Chemistry, Graduate School of Science and Engineering, Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan |
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Abstract: | Benzylic carboxylates were found to react with Pd(0) complexes bearing tertiary phosphines to give benzylpalladium(II) carboxylate complexes with cleavage of the benzyl-oxygen bond. The benzylpalladium complexes having the trifluoroacetato ligand react with olefins such as ethyl acrylate to give olefin benzylation products. On the basis of these studies a novel palladium-catalyzed benzylation of olefins was developed without using organic halides as the starting materials. The method has another advantage of requiring no base as in the conventional Mizoroki-Heck process using organic halides. The catalytic cycle is proposed to be constituted of elementary processes of (a) oxidative addition of a benzyl carboxylate with C-O bond cleavage to a Pd(0) complex to give a benzylpalladium carboxylate, (b) olefin insertion into the benzylpalladium bond to give an alkylpalladium complex, and (c) β-H abstraction to liberate the benzylated olefin. |
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Keywords: | Benzylation Palladium catalyst Benzyl-O bond cleavage Olefin synthesis Benzylpalladium carboxylate |
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