Palladium-Catalyzed [3+2] Cycloaddition of Trimethylenemethane with p-Benzoquinones
Takashi MUKAWA and Shinsaku SHIRAISHI*
Institute of Industrial Science, The University of Tokyo; Roppongi, Minato-ku, Tokyo106-8558 Japan
The reaction of trimethylenemethane with various alkyl-substituted p-benzoquinones was investigated. The reaction of 2,5-di-tert-butyl-p-benzoquinone with 2-(trimethylsilylmethyl)allyl acetate (1) was conducted with palladium(0) as a catalyst to afford 1 : 1-C=C-cycloadduct 2 in good yield. Similarly, 1 : 1-C=C-cycloadducts 3, 4, 5 and 6 were obtained with 2,6-di-tert-butyl-p-benzoquinone, 2,3,5,6-tetramethyl-p-benzoquinone, 2,3,5-trimethyl-p-benzoquinone and 2-methyl-1,4-naphthoquinone, respectively. On the other hand, the reaction with methyl-p-benzoquinone afforded the complicated mixture. As is the case with Diels-Alder reactions, the cycloaddition of trimethylenemethane with p-benzoquiones occurred towards C-C double bond. So, the reaction of trimethylenemethane with substituted p-benzoquinones is effective in the synthesis of methylenecyclopentane-fused cyclohexenediones having various substituents.
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