| Abstract: | Cycloadditions with ionic components are known as “polar cycloadditions” to distinguish them from cycloadditions with dipolar and uncharged components. The structural requirements, the manner in which “polar” intermediates capable of addition are produced and their reactivity with activated and nonactivated multiple bonds, the many peculiarities of the course of the cycloaddition, and the favorable synthesis of heterocyclic systems by this reaction principle makes such a terminological distinction useful and necessary if the existing data are to be brought into order. The present review, which is the first on a field of chemistry that has not yet been very extensively investigated, deals initially with cationic and then with anionic polar cycloadditions. |
