Paper
Synthesis of Octachlorobicyclo[3.3.0]octa-1,4,6-triene and Lewis Acid Catalyzed Isomerization of Hexachlorobicyclo[3.3.0]octa-3,5,8-trien-2-one
Published Feb 1, 1983 · K. Kusuda
Bulletin of the Chemical Society of Japan
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Abstract
Treatment of decachloro(4-allylidenecyclopentene) with enneacarbonyldiiron(0) gave octachlorobicyclo[3.3.0]octa-1,3,7-triene (δ-C8Cl8) in 40% yield. Dechlorination of decachlorobicyclo[3.3.0]octa-2,6-diene with powdered selenium, sulfur, phosphorus, or titanium in the presence of anhydrous aluminium chloride without any added solvent at 90–100 °C afforded octachlorobicyclo[3.3.0]octa-1,4,6-triene (2) (e-C8Cl8) in good yield. Hexachlorobicyclo[3.3.0]octa-3,5,8-trien-2-one obtained from 2 was chlorinated by a concentrated solution of antimony(V) chloride in refluxing dichloromethane to give octachlorobicyclo[3.3.0]octa-3,6(or 7)-dien-2-one, but in a dilute solution (less than 0.1 g of antimony(V) chloride/cm3 of dichloromethane) hexachlorobicyclo[3.3.0]octa-4,6,8-trien-2-one (14) was obtained. Mechanism of the isomerization is discussed in terms of antiaromaticity of cyclopentadienyl cation. Reaction of 14 with methanol afforded pentachloro-4-methoxybicyclo[3.3.0]octa-3,5,7-trien-2-one. Ethanol or 2-propano...
Octachlorobicyclo[3.3.0]octa-1,4,6-triene and its isomerization with methanol or 2-propanol provide valuable insights into the synthesis of cyclopentadienyl cations and their derivatives.
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