Flexibility vs Rigidity of Singly and Doubly Tethered Biphenyls: Structure, Dynamic Stereochemistry, and Resolution of Tribenzo[a,c,f]cyclooctane, Tetrabenzo[a,de,h,kl]bicyclo[6.6.0]tetradecane, and Their Alkyl Derivatives.

The barrier for enantiomerization of tribenzo[a,c,f]cyclooctane (1a) as acquired from dynamic (1)H NMR experiments was found to be DeltaG() = 19.5-20.1 kcal mol(-)(1), and DeltaG() = 17.