| Abstract: | Intramolecular overcrowding in bistricyclic enes ( 1 ) requires out-of-plane deformations in order to accommodate the sterically demanding tricyclic moieties without prohibitively close contacts of nonbonded atoms. The nonplanarity of 1 introduces the notion of chirality to the arena of overcrowded aromatic enes. Deviation from coplanarity occurs by twisting around the double bond and out-of-plane bending (hence pyramidalization). The bending is realized by folding of the tricyclic moieties. The conformations of homomerous ( 1 , × = Y) and heteromerous ( 1 , × ≠ Y) bistricyclic enes and their mono- and disubstituted derivatives are analyzed along with their point group symmetries and chirality. The implications are illustrated using the structures of characteristic examples calculated with the semiempirical method PM3. © 1995 Wiley-Liss, Inc. |
