Dicyclopenta cyclooctanes

The dicyclopenta[a,characteristic element of some terpenoids was obtained in 100% yield by a very facile Cope rearrangement of the highly functionalized divinylcyclobutane derivative 533 on heating in benzene at 55 °C for 4 h. The mild conditions can be due to participation of the lone pair of the sulfur atom or to the strain energy of the divinylcyclobutane fragment (equation 206)259. 

Intramolecular [ 2 + 2] photoadditions in sulphur-containing systems have been employed in studies directed towards the total synthesis of dicyclopenta[a,d]cyclooctane terpenoids and in the conversion of the tetrathiadiene (145) into the propellane (146), a process in which the ease of reaction is... 

For a stereoconvergent approach to dicyclopenta[tf,d]cyclooctane terpenoids via a Cope rearrangement of a highly functionalized divinylcyclobutane derivative see ref 1013. 

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