Easy Access to Esters with a Benzylic Quaternary Carbon Center from Diallyl Malonates by Palladium-Catalyzed Decarboxylative Allylation

Daisuke Imao, Akihiro Itoi, Asako Yamazaki, Masamichi Shirakura, Ryota Ohtoshi, Kenta Ogata, Yohki Ohmori, Tetsuo Ohta,* and Yoshihiko Ito†
Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394, Japan
J. Org. Chem., 2007, 72 (5), pp 1652–1658
DOI: 10.1021/jo0621569
Publication Date (Web): January 30, 2007
Copyright © 2007 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

,
†

 Dedicated to the hearty memory of the late Professor Yoshihiko Ito of Doshisha University. Deceased on December 23, 2006.

, tota@mail.doshisha.ac.jp

Abstract

Abstract Image

Diallyl 2-alkyl-2-arylmalonates underwent palladium-catalyzed decarboxylative allylation quickly under mild conditions. In contrast, no reaction took place with diallyl 2,2-dialkylmalonates under the same conditions. Electron-donating phosphine ligands were found to be vital for this reaction. Most of the solvents used did not affect the catalytic cycle. Catalysis in [bmim][BF4], a well-known ionic liquid, was inhibited as a result of formation of a hydrogen bond between a carboxylate anion and a [bmim]+ cation; however, the reaction in [bdmim][BF4], in which the acidic proton of [bmim][BF4] was replaced with a methyl group, proceeded smoothly. The catalytic mechanism was investigated using a tetradeuterated substrate and an enzymatically synthesized enantio-enriched allyl methyl 2-methyl-2-phenylmalonate. Even the electron-deficient phosphite ligand was found to be active for catalysis of diallyl 2-methyl-2-(2- or 4-nitrophenyl)malonates.

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History

  • Published In Issue March 02, 2007
  • Received October 17, 2006

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