1,11-Dilithio-5,5,7,7-tetramethyl-5,7-dihydrodibenz[c,e]oxepin (3; shown as I) is a conformationally confined analog of o,o'-dilithiobiphenyl (1). A temp. variable NMR study of this model compd., monitoring the coalescence of its diastereotopic Me groups, ...
1994