This product could be obtained pure (isolated yield ca.
5 %) by preparative gas chromatography under mild conditions. Its CCl,) showed it to have the structure of a hexacyclo-[4.4.0.02~4.03~9.05~7.08~'o]decane ( 4 ) . The spectrum contained three signals in the intensity ratio 3:1:6 [T = 7.16 (m, 3H), ~= 7 . 4 2 (m, IH), r=8.37 (m, 6H)]. The neighborhood relationship of the three types of protons was proved by double resonance experiments : irradiation at T = 7.16 converted the signal at T = 8.37 into a singlet, and irradiation at ~= 8 . 3 7 converted the signal at ~= 7 . 1 6 into a singlet and that at T = 7.42 into a quadruplet. The molecular formula CloHlO was confirmed by highresolution mass spectrometry. The IR spectrum is in accord with the proposed structure (point group C3J. The compound shows only end absorption in its UV spectrum.
'Diademane' (4) forms highly volatile, colorless crystals melting at 9697°C (with rearrangement). When warmed it rearranges smoothly to triquinacene (5) f l l l (half-reaction time ca. 60min at 90°C), which was identified by means of its characteristic 'H-NMR spectrum. This -[2. + 2, + J,]-cycloreversion, which is an allowed con-
certed process according to the principle of conservation of orbital symmetry ['21, is perhaps here made extra easy by the considerable ring strain which, according to models, appears to be present in the molecule.
Attempts to determine this strain energy and to study the electronic interaction between the three cyclopropane rings of (4) by means of photoelectron spectroscopy are in progress.