Synthesis and Electron‐Diffraction Structure of all‐cis‐[5.5.5.5]Fenestrane

Abstract The efficient synthesis of all‐ cis ‐[5.5.5.5]fenestrane ( 2 ) from the readily available intermediate 3 allowed the electron‐diffraction analysis of 2 . This structure analysis revealed long C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 D 2 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°.