Polycyclic compounds cycloalkenes

More research efforts have focused on the ring-closing enyne metathesis, which usually [176] provides conjugated vinyl cycloalkenes (cf Fig. 2a, exo mode) useful for further manipulation, but also allows tandem metathesis processes for the formation of polycyclic compounds. 

Although Hantzsch-Widman system works satisfactorily (if you can remember the rules) for monocyclic compounds, it is cumbersome for polycyclic compounds. In the case of oxiranes it is simplest for conversational purposes to name them as oxides of the cycloalkenes or epoxy derivatives of the corresponding cycloalkanes. The oxabicycloalkane names seem preferable for indexing purposes, particularly because the word oxide is used in many other connections. 

Alicyclic Hydrocarbons. These refer to cyclic analogues of aliphatic hydrocarbons and are named accordingly, using the piefix cyclo-." Their properties are similar to their open-chain aliphatic counterparts. Alicyclic hydrocarbons are subdivided into monocyclic (cycloalkanes, cycloalkenes, cycloalkynes, cycloalkadienes, etc.) and polycyclic aliphatic compounds. Monocyclic aliphatic structures having more than 30 carbon atoms in the ring are known, but those containing 5 or 6 carbon atoms are more commonly found in nature [47, p. 28]. 

Many cyclic and polycyclic (more than one ring) compounds containing double bonds are known, including a great many natural products. Figure 3.43 shows some common structures incorporating cycloalkenes. 

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