Through-bond transmission of polar substituent effects in the bicyclo [2.2.2]octane ring system as monitored by 119Sn NMR chemical shifts: A 119Sn NMR study of 10-substituted 9-trimethylstannyltriptycenes

A series of 10‐substituted(X)‐9‐trimethylstannyltriptycenes (2a) were synthesized and characterized and the 119Sn chemical shifts measured. Comparisons were made of the 119Sn 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 119Sn shifts of the latter system. A more restricted series of 10‐substituted(X)‐9‐methyltripycenes (2c) were acquired and their 13CH3SCS compared with those of the corresponding bicyclo[2.2.2]octanes (1c). Significant ‘through‐bond’ contributions are also indicated for the latter system.