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Condensation reactions of benzaldehyde catalysed by gold alkoxides

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Abstract

Condensation reactions between active methylene compounds, CH2(X)(Y), such as alkyl cyanoacetate or acetophenone and benzaldehyde proceed smoothly in the presence of Catal.ytic amounts of gold alkoxides, Au(OR)L (L=PPh3: R=CH2CF3 (la), CH(CF3)2 (lb); L=PCy3: R=CH2CF3 (1c), CH(CF3)2 (1d) or AuMe2(OR)L (L=PPh3: R=CH2CF3 (2a), CH(CF3)2 (2b). Gold(I) complexes show higher catalytic activity than gold(III). In the catalytic system, the catalysts exist as the C-bonded gold enolate complexes Au(I)(CH(X)(Y))(L) or Au(III)Me2(CH(X)(Y))(L), which can be isolated independently from the reactions of gold alkoxides with the corresponding active methylene compounds. The catalytic activity of the gold alkoxides is generally higher than that of isolated C-bonded gold enolates. The reaction rate increases with increase in the concentrations of catalyst and benzaldehyde, but is independent of the concentration of alkyl cyanoacetate. A reaction mechanism involving two catalytic pathways has been proposed.

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Professor Sanshiro Komiya has worked in the Department of Applied Chemistry at Tokyo University of Agriculture and Technology since 1989 and studies the organometallic chemistry of transition metals, including gold. Drs Atsushki Fukuoka and Masafumi Hirano are members of kProfessor Sanshiro’s research group. Takuo Sone and Yoko Usui are graduate students in the Department

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Komiya, S., Sone, T., Usui, Y. et al. Condensation reactions of benzaldehyde catalysed by gold alkoxides. Gold Bull 29, 131–136 (1996). https://doi.org/10.1007/BF03214748

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Keywords

  • Benzaldehyde
  • Alkoxide
  • Acetophenone
  • Malononitrile
  • Cyanoacetate