Synthesis and Electron-Diffraction Structure of all-cis-[]Fenestrane



The efficient synthesis of all-cis-[]fenestrane (2) from the readily available intermediate 3 allowed the electron-diffraction analysis of 2. This structure analysis revealed long C[BOND]C bonds in the central C(C)4 fragment and a twist-envelope conformation for the four cyclopentane substructures. The four bridgehead H-atoms are in a synclinal rather than an ecliptic position with an approximate D2 symmetry of 2. Planarizing distortions are evident from the opposite bond angles at the central C-atom being 116.2 ± 0.5° with the remaining four being 103.7 ± 0.2°.