Recent discoveries have shown that allylic cations will cycloadd both intermolecularly and intramolecularly to 1,3-dienes. A detailed investigation of these cyclo-addition reactions is planned. Initial studies will involve a systematic investigation of suitable cation precursors and of diene substituents which are useful in these reactions. Reaction conditions will be explored, with special attention to the generation of allyl cations under both acidic and basic (or neutral) reaction conditions. The use of cyclopropylcarbinyl cations in place of allyl cations will be explored. In this way, we believe that we will be able to devise simple one step syntheses of bicyclo[4.3.0]nonanes, bicyclo[4.4.0]decanes, and bicyclo[5.3.0]decanes from acyclic-precursors. In addition the tricyclo[5.3.1.0/5,10]undecane skeleton should be available from monocyclic precursors. In this way, such naturally occurring systems such as the cadinanes, guianes, and patchouli derivatives should become readily accessible.