2.80 A and represents the most extreme example of face to face crowding of two aromatic rings presently known. The physical and chemical properties of 11 and its derivatives are discussed. The chemical effects of this interfacial crowding are especially evident in the facile conversion of 15 to the novel cage structure 24. ecently, we have described a procedure for the R transformation of a sulfide linkage to a carboncarbon double bonda3 ...