Synthesis, including asymmetric synthesis, of 1-substituted cyclopentenes from cyclobutanones with one-carbon ring-expansion by 1,2-carbon-carbon insertion of magnesium carbenoids |
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Authors: | Tsuyoshi Satoh Yu AwataYuichi Kato Shingo OgataMasashi Ishigaki Shimpei SugiyamaHideki Saitoh |
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Affiliation: | Graduate School of Chemical Sciences and Technology, Tokyo University of Science; Ichigaya-funagawara-machi 12, Shinjuku-ku, Tokyo 162-0826, Japan |
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Abstract: | Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were derived from cyclobutanones and chloromethyl p-tolyl sulfoxide, with lithium enolate of tert-butyl carboxylates, amides, lithium α-sulfonyl carbanions, and lithium α-carbanion of acetonitrile gave adducts in high to quantitative yields. The adducts were treated with Grignard regents, such as i-PrMgCl and EtMgCl in toluene to afford 1-substituted cyclopentenes in good to high yields with one-carbon ring-expansion via 1,2-carbon-carbon (1,2-CC) insertion reaction of the generated magnesium carbenoid intermediates. The magnesium carbenoid 1,2-CC insertion was found to be highly stereospecific. When optically pure chloromethyl p-tolyl sulfoxide was used in this procedure, optically active 1-substituted cyclopentenes were obtained in high optical purity. |
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Keywords: | Cyclopentene Magnesium carbenoid 1,2-Carbon-carbon insertion One-carbon ring-expansion Rearrangement |
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