In,out-isomerism of phosphorus bridgehead cage compounds.: A review

The chemistry and stereochemical peculiarities, especially the phenomenon of in, out-isomerism of bi- and polycyclic compounds with one or more phosphorus bridgehead atoms, are reviewed in the present paper. The appearance of in, out-isomers depends on the ring size of the bi- and polycycles. In general graphic in, out-isomerism becomes only possible in medium sized ring systems and in particular in macrocyclic compounds. However even bicyclic systems containing small rings can be trans-configured if the third chain is long and flexible enough hence giving rise to pseudo-in, out-isomerism. In-phosphorus atoms exhibit a low reactivity in comparison to their out-counterparts. Nevertheless some few examples of reactions at in-positioned phosphorus atoms have been presented. This will potentially open the way to a specific modification of the cavity of such macrobi- and polycyclic compounds. A review with 53 references.