Cyclophanes 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). 

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... 

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). 

All members in the series of [2 ]cyclophanes [3] up to the sixfold-clamped superphane [4] are known today. Among the [n]paracyclophanes [5] bridging with a pentamethylene chain has established an end point so far and in the case of the syntheses of multilayered [2 J cyclophanes [6] a limit of six stacked benzene rings has been achieved. 

Fig. 31a. Reaction path to a new class of superphanes containing cobalt stabilized orrti-aromatic n-decks and b. 135 as a useful intermediate for the preparation of various cyclophane complexes [112-114]...

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