Diels-Alder Approaches for the Synthesis of Bridged Bicyclic Systems: Synthetic Applications of (7-hetero)norbornadienes

Molecules containing bridged bicyclic systems, such as the (7-hetero)bicyclo[2.2.1]heptane ring system, are interesting synthetic targets because these systems are present in many molecules with biologically relevant activity. Common precursors for these sytems are the (7-hetero)nobornadienes. This review covers the different approaches used in the last ten years for the synthesis of (7-hetero)norbornadienes through Diels-Alder (D-A) cycloaddition between cyclic dienes and alkynes. The review also shows the synthetic applications of these [2.2.1]bicyclic systems as intermediates in the preparation of other relevant molecules.