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The reaction of cyclooctadeca-I ,I 0-diyne with (~4-cyclooctadiene)(~~-cyclopentadienyl)cobalt gives in low yields the Co ( C5 H 5) -st a b i I ized cy c I o but a d i e n e s u p e r p h a n e with f o u r h e pt a m et h y I e n e b r i dg es .In his seminal paper on the conformation of polycyclic ring systems, J. Dale showed that if one connects two x-systems with uneven chains of equal length a strain-free zig-zag conformation of the chains is adopted.' In the case of even chains no strain-free conformation is possible. This might be one of the reasons why the formation of superphanes of metal-stabilized cyclobutadiene has been reported only from cyclodeca-l,6-diyne la2 and cyclotetradeca-1 ,&diyne lc.3 In both cases the four chains between the cyclobutadiene moieties adopt a strain-free conformation.In the case of cyclododeca-l,7-diyne l b only the intramolecular cyclization product 3b has been found.4 The observations so far5 suggest that for cyclohexadeca-l,9-diyne Id only the intramolecular product 3d should be formed while for cyclooctadeca-1 ,lo-diyne l e the superphane 4e seems a likely @ n = 3, 4, 5, 6, 7 a b c d e 4

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The fourfold bridged tricyclo[4.2.0.02~5]octa-3,7-diene derivative 3 reacts with diazomethane and m-chloroperbenzoic acid (mCPBA) to yield the monoadduct 5 in good and the bisadduct 4 in poor yield as well as the mono-and bisepoxides 7 and 8 in good yields, respectively. Also the "mixed product 6 is obtained. All five compounds are strained propellanes. The Xray crystallographic structure analysis of 8 reveals a distance of 2.812 A between the epoxide rings.Cage compounds have fascinated chemists for many They are not only appealing because of their usually high symmetry but also represent versatile model compounds. Due to their rigid geometry they are used as models for cycloaddition reactions, for the study of long-range interactions and for the investigation of the geometrical conditions for electron transfer, to name only a few examples. Chem.