Highly stereoselective protonation of the enolate of a bicyclic cycloheptatrienyl lactone occurs on the hindered face.
[reaction: see text] The H/D exchange of the lactone-fused cycloheptatriene 1 is over 1000 times faster than that of the epimer 2. Interconversion of 1 and 2 provides an equilibrium mixture of 1:0.7, showing a similar stability of the isomers. Protonation of the common enolate 7 occurs far more readily on the more hindered face. Cycloheptatrienide anion is bent and as stable as a divinylcarbanion.
Sugimura
Takashi
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Graduate School of Science, Himeji Institute of Technology, Kohto, Kamigori, Ako-gun, Hyogo 678-1297, Japan. sugimura@sci.himeji-tech.ac.jp
Kim
Wan Hyeok
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Kagawa
Masami
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Okuyama
Tadashi
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