Endo-Exo Convention 1) the position of double bonds relative to rings in carbocyclic systems; 2) the relative orientation of substituents of bridged carbocycles; 3) opposing pathways for certain intramolecular cyclization and cleavage reactions; 4) opposing pathways for Diels-Alder type cycloaddition reactions based on the orientation of dienes to dieneophiles.

Alkene Orientations Ring Bridging 1) a bridge containing a heteroatom or atoms 2) a shorter bridge 3) a saturated bridge 4) a less substituted bridge 5) a bridge with the lowest CIP priority substituents

INTRAMOLECULAR CYCLIZATIONS

Example 1. Endocyclic and exocyclic double bonds: In the compound chamigrene, which was stereoselectively synthesized by transannular cyclopropanation followed by ring fragmentation, there is both an endocyclic double bond and an exocyclic double bond

Example 2. 2,6-Dimethylbicyclo[3.3.1]nona-3,7- diene-endo-2,endo-6-diol. The short bridge takes precedence over the unsaturated bridges

For each bridged compound below, identify the reference bridge and specify the endo/exo orientation of "W" substituent