A new method for introducing an ethylenic bridge via a cycloaddition reaction has been developed. It makes use of either (Z)- or (E)-1,2-bis(phenylsulfonyl)ethylene (5 or 6) as synthetic equivalents of acetylene. The high activation due to the two sulfonyl groups promotes cycloadditioti even to very unreactive dienes. The removal of the two sulfonyl groups for the required formation of the carbon-carbon double bond is promoted by reduction with metal amalgams in high yields. These properties, associated with the stability of the reagents and the ease of performance of the reactions, make this method a very useful synthetic tool for the preparation of polycyclic dienes and a valid alternative to the commonly available reagents that largely depend upon oxidative methods. © 1984, American Chemical Society. All rights reserved.
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