Dihetero-isotwistanes and -twistanes

Starting Material 2,7-Dihetero-isotwistanes and -twistanes as Well as... 

Restriction among the great number of possible dihetero-tricyclodecanes to such with a carbocyclic 8-membered ring (cyclooctane) as basic skeleton, which is crosswise bridged by two heteroatoms, and restriction to 5-, 6- and 7-membered heterocyclic rings, isomeric dihetero-tricyclodecanes of the following five different stmctural types are possible 2,6-dihetero-adamantane (G 7 ) 2,7-dihetero-isotwistane (G 2,7-dihetero-twistane (G S) 2,8-dihetero-homotwistbrendane (G 4) and 2,6-dihetero-tricyclo[3.3.2.0 Jdecane (G 5) . 

The first synthesis of a tricyclo[4.3.1.0 ]decane, namely of pure carbocyclic iso-twistane [G 2 X(2) = CHj, Y(7) = CHj ], was reported by Vogt S in 1968. Almost at the same time 2,7-dihetero-isotwistanes (G 2) and/or derivatives thereof became available. Today a variety of such compounds are known ... 

In the series of dihetero-tricyclodecanes, substitutions and rearrangements involving neighboring group participation of heteroatoms (onium ions) especially of oxygen (oxonium ions) sulfur (episulfonium ions, thiiranium ions) and nitrogen (ammonium ions, aziridinium ions) as well as in one case also of selenium (epi-selenium ions), were studied on adamantanes (G1), isotwistanes (G 2), twistanes (G 2) and homotwistbrendanes (G 4). 

Starting from dihetero-tricyclodecanes described in the Sections 2. and 3. of the types of adamantane G1), isotwistane (G 2), twistane (G 3) and homotwistbrendane (G 4), which in their turn were prepared either by cyclization of suitable 9-heterobicyclo-... 

Between approx. 1200 and 800 cm all dihetero-tricyclodecanes show marked sharp absorption bands. Comparing, e.g. the spectra of unsubstituted skeletal isomers, already gives good hints for the assignment of a certain structure type because compounds of higher symmetry exhibit less absorption bands than those of lower syih-metry [e.g. 2,7-dioxa-twistane 212) and 2,7-dioxa-isotwistane 128), resp.]. 

For tricyclo[4.3.1.0 ]decane the following trivial names were introduced in the literature isoadamantane (1968) protoadamantane (1968) isotwistane (1969) and 2(3 - 4)abeo-adamantane (1970) In the present review the name isotwistane will be applied, which until now is exclusively used to describe such 2,7-dihetero-tricyclodecanes. However, one should pay attention to the fact that since 1972 the trivial name iso-twistane is also applied for tricyclo[4.3.1.0 )decanes. 

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