Superphanes

Syntheses of cyclophanes with more than two bridges have led to the ultimate achievement of a fully bridged [2.2.2.2.2.2](l,2,3,4,5,6)cyclophane, the so-called superphane 29). It is of course achiral as well as the three isomeric [2.2.2]cyclophanes31). 

An interesting series of polycyclic olefins with notable pyramidalization in the lower members is represented by the superphanes 37142 and 38143. Their pyramidalization angles are shown in Table 6. While 37 could be obtained as a solid at ambient temperature... 

The thermolysis of cobalt complex 116 in the presence of copper powder at 190 °C gave 10-membered cyclic acetylene 117 (Scheme 4) <2002AGE1181>. The reaction was iterated to lead to belt-like macrocycles. The same procedure was also utilized to synthesize twofold CpCo-capped bis(cyclopentadieno)superphane <20000M1578>. 

In light of the mass spectrometric results described above, a rational fullerene synthesis from cyclophyne precursors appears to be within reach. Since superphane 21 [43] and superferrocenophane 22 [44] are established structural precedences, it may well be that reports about a successful synthesis of superphyne 23, an acetylenic isomer of buckmin-sterfullerene, or even a corresponding supermetallophyne are only a short time away. 

Seventeen years after Boekelheide s landmark synthesis of [2f,](l, 2, 3, 4, 5, 6)cyclophane (also known as superphane) [36], Shinmyozu very recently described the synthesis of the homologous superphane [3 ](l, 2, 3, 4, 5, 6)cyclophane (53, Scheme 12) [37], Formation of the I inal bridge of this molecular pinwheel was accomplished with an intramolecular aldol condensation. While the double bond of enone 50 could be... 

Other superphanes of note are CpCo-capped cyclobutadiene and cyclopentadienone-contain-ing superphanes prepared by Gleiter s group. Examples of these are 55-57 (Scheme 13) [41]. 

Superphanes, Cyclophanes, and Betweenanenes. The simplest member of the superphanes, tricyclo[4.2.2.22,5]dodeca-l,5-diene (56) (cf. Table 5) has been experimentally and theoretically described by Wiberg and co-workers (57b, 85). Ab initio as well as molecular mechanics calculations reproduce the structural features and the pyramidalization in 56 as observed in X-ray analysis rather well. Due to the small distance between them, the two pyramidalized double bonds interact with each other (85). Using the CCF method, Ermer has discussed the structure of columnenes 70-72 (11). Ab initio studies gave, for these columnenes pyramidalization angles T of 18.2°, 29.3°, and 47.3°, respectively strong through-space n-n interactions were found in all three (86). 

Pyramidalization is not limited to superphanes. Suitably short para and meta bridges induce significant departures from planarity also in cyclophanes. Typical examples, where the deformation is spread over more than one formal double bond, are given by the highly strained [2.2]paracyclophane (73) and the [m]paracyclophanes (m = 6-12) (74) (87). Evidence for a still smaller member of this family of compounds, [4]paracyclophane 75, has recently been reported (88). Essentially no structural or computational results have been reported for betweenanenes. These are bicyclic compounds of type 76, in which formally two trans-cycloalkcnes share the double bond. This structural relationship suggests a /llu-type deformation for the highly shielded double bond, similar to that found in overcrowded olefins (89). 

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