Bridgehead-Substituted Bicyclo[3.3.1]Ronehes and Their Benzo and Dibenzo Derivatives

摘要

Bridged bicydic molecules with halogens at bridgehead positions have played key roles in establishing geometrical requirements for formation of carboeations, carbanions, and free radicals. Studies of 1-halotriptycenes and other derivatives of 1-halobicyclo[2.2.2]octenes, for instance, have demonstrated the lack of resonance stabilization of carbocations in systems in which adjacent pi-bonds are essentially orthogonal to the cationic centers. Less evidence is available, however, as to the extent of resonance stabilization of bridgehead carbocations and other reactive intermediates in larger unsaturated bicyclic systems. This appears to be due to the absence of good methods for the Synthesis of such systems.