THROUGH-BOND TRANSMISSION OF POLAR SUBSTITUENT EFFECTS IN THE BICYCLO-[2.2.2]OCTANE RING-SYSTEM AS MONITORED BY SN-119 NMR CHEMICAL-SHIFTS - A SN-119 NMR-STUDY OF 10-SUBSTITUTED 9-TRIMETHYLSTANNYLTRIPTYCENES

A series of 10-substituted(X)-9-trimethylstannyltriptycenes (2a) were synthesized and characterized and the Sn-119 chemical shifts measured. Comparisons were made of the Sn-119 substituent chemical shifts (SCS) of 2a and the corresponding values of 4-substituted(X)bicyclo[2.2.2] oct-1-yltrimethylstannanes (1a), which confirm the previous conclusion that 'through-three-bond' effects or double-hyperconjugation strongly regulate the Sn-119 shifts of the latter system. A more restricted series of 10-substituted(X)-9-methyltripycenes (2c) were acquired and their (CH3)-C-13 SCS compared with those of the corresponding bicyclo[2.2.2]octanes (1c). Significant 'through-bond' contributions are also indicated for the latter system.