Asterans

from Wikipedia, the free encyclopedia

Asteranes (from ancient Greek ἀστήρ astēr and Latin astrum for "star") are a group of polycyclic hydrocarbons with a star-like cage structure . These compounds are derived from cyclohexane from rings which in the boat conformation are linked to "bug" and "rear" with each other. The boat conformation, which is more energetic and therefore more unstable than the chair conformation , is thereby fixed.

  • Chair conformation

  • Boat conformation

The name asterane was coined in 1965 by Hans Musso , whose working group dealt with the synthesis of various representatives of these hydrocarbons in the following years.

Structures

Depending on the number of cyclohexane units in the molecule, the representatives of the group of substances are referred to as di-, tri-, tetra-, pentaasteranes, etc.

chemical structure of asterans

1: diasterane, 2: triasterane, 3: tetraasterane, 4: pentaasterane,
5: hexaasterane, 6: heptaasterane

properties

Of interest in the asteranes is the 1,4-interaction of the hydrogen atoms between "bow" and "stern" in the cyclohexane tub conformation; the distance between these H atoms decreases from tri-, through tetra- to pentaasterane.

1,4-HH distances in tri-, tetra- and pentaasterane

1,4-HH distances in tri-, tetra- and pentaasterane

The boat conformation, which is energetically less favorable from the start, is made even more unfavorable by this pressing together of the “bow” and “stern”, so that unusual bond lengths, bond angles and intramolecular distances result, which are reflected in unusual spectroscopic and chemical properties.

Representation of asterans

So far, syntheses of di-, tri- and tetraasterane have been published.

Triasteran

The first example of asterane synthesis was the preparation of triasterane in 1965. First, 1,4-cyclohexadiene 1 is reacted with diazomalonic acid diethyl ester 2 with copper catalysis to form norcarenedicarboxylic acid diethyl ester 3 . The saponification with KOH gives the norcarenedicarboxylic acid 4 , which can be decarboxylated to norcarene carboxylic acid 5 at 200.degree . The acid chloride 6 is obtained by reaction with oxalyl chloride and reacts with diazomethane to form the diazoketone 7 . This decomposes in boiling hexane and in the presence of Cu powder with elimination of nitrogen to form the triasteranone 8 . The Wolff-Kishner reduction with hydrazine and potassium hydroxide (KOH) yields the triasterane 9 .

Multi-step synthesis of tristerane from cyclohexadiene

Multi-step synthesis of triasterane from cyclohexadiene

Tetraasterane

A Tetraasterane synthesis published in 1975 starts from 3,6-dihydrophthalic anhydride 1 . The dimeric anhydride 2 , in which the tetraasterane skeleton is already present, is obtained by exposure to dioxane . The anhydride is broken down into tetracarboxylic acid 3 , which can be converted into tetrachloride 4 in a Kochi reaction according to a variant by Cyril A. Grob with lead tetraacetate and N -chlorosuccinimide . Intermediate product 4 is reduced to tetraasterane 5 with sodium .

Multi-step synthesis of tetraasterane from 3,6-dihydrophthalic anhydride

Multi-step synthesis of tetraasterane from 3,6-dihydrophthalic anhydride

The bis-tetraasterane is a compound with two linked tetraasterane units.

Diasterane

The synthesis of diasterane was achieved in 1986 in a multistep reaction. Starting from tricyclo [4.2.1.1 2,5 ] decane 1 , photochemical bromination in carbon tetrachloride at 140 ° C. gives bromide 2 , which can be converted into olefin 3 by dehydrobromination with DBU . The alcohol 4 , which is oxidized to the ketone 5 with dimethyl sulfoxide and oxalyl chloride, is accessible by hydroboration . The diazoketone 6 is obtained by α- formylation and subsequent reaction with tosylazide . The photolysis and Wolff rearrangement of this compound gives the endo methyl ester 7 and after ester hydrolysis exo carboxylic acid 8 . The decarboxylation to tricyclo [3.2.1.1 2,4 ] nonane 9 can be carried out by a method by Derek HR Barton et al. be performed. By repeating the same reaction sequence, a ring narrowing is achieved in the second half of the molecule and the diasterane 10 is obtained .

Multi-step synthesis of diasterane from tricyclo [4.2.1.12,5] decane by double ring contraction

Multi-step synthesis of diasterane from tricyclo [4.2.1.1 2,5 ] decane by double ring contraction

Hypothetical asterans

Despite several attempts and different methods, the pentaasterane could not yet be synthesized. It is thus, like the next two compounds in the asterane series - the hexa- and the heptaasterane - a hypothetical connection.

See also

Individual evidence

  1. ↑ Entry on Asterane. In: Römpp Online . Georg Thieme Verlag, accessed on October 6, 2019.
  2. ↑ a b U. Biethan, Uv Gizycki, H. Musso: Asterane . In: Tetrahedron Letters . tape 6 , no. January 20 , 1965, p. 1477 , doi : 10.1016 / s0040-4039 (00) 90092-3 .
  3. ^ Henning Hopf: About Hans Musso (1925–1988) and his scientific work . In: Chemical Reports . tape 125 , no. February 2 , 1992, doi : 10.1002 / cber.19921250202 .
  4. ↑ Uwe Biethan, Hans Musso: endo- and exo-Δ 3 -Norcaren-carboxylic acid- (7) . In: Chemical Reports . tape 97 , no. 8 , August 1964, p. 2282 , doi : 10.1002 / cber.19640970826 .
  5. ↑ External identifiers of or database links to Tetracyclo [3.3.1.0 2,8 .0 4,6 ] nonane : CAS number: 3105-29-1, PubChem : 137827 , ChemSpider : 121477 , Wikidata : Q74755828 .
  6. ↑ K. BECKER, M. GEISEL, C. GROB, F. KUHNEN: Improved Preparation of Tertiary Chlorides by Halodecarboxylation . In: Synthesis . tape 1973 , no. 08 , March 18, 2002, p. 493 , doi : 10.1055 / s-1973-22243 .
  7. ↑ External identifiers of or database links to pentacyclo [6.4.0.0 2.7 .0 4.11 .0 5.10 ] dodecane : CAS number: 259-77-8, PubChem : 12316943 , ChemSpider : 16736514 , Wikidata : Q74754213 .
  8. ↑ Hans-Martin Hutmacher, Hans-Günter Fritz, Hans Musso: Tetraasterane, Pentacyclo [6.4.0.0 2.7 .0 4.11 .05.10] -dodecane . In: Angewandte Chemie . tape 87 , no. 5 , March 1975, p. 174 , doi : 10.1002 / anie.19750870511 .
  9. ↑ Volker Thomas Hoffmann, Hans Musso: Asterane, XXII. Synthesis of a double tetraasterane: Nonacyclo [10.8.0.0 2.11 .0 4.9 .0 4.19 .0 6.17 .0 7.16 .0 9.14 .0 14.19 ] eicosane . In: Chemical Reports . tape 124 , no. 1 , January 1991, pp. 103 , doi : 10.1002 / cber.19911240118 .
  10. ^ Derek HR Barton, David Crich, William B. Motherwell: The invention of new radical chain reactions. Part VIII. Radical chemistry of thiohydroxamic esters; A new method for the generation of carbon radicals from carboxylic acids . In: Tetrahedron . tape 41 , no. January 19 , 1985, p. 3901 , doi : 10.1016 / s0040-4020 (01) 97173-x .
  11. ↑ Andreas Otterbach, Hans Musso: Diasterane (Tricyclo [3.1.1.1 2.4 ] octane) . In: Angewandte Chemie . tape 99 , no. 6 , June 1987, pp. 588 , doi : 10.1002 / anie.19870990624 .
  12. ^ Klaus Ebel, Heinz Krüger, Hans Musso: Asterane, XX. Studies in the Pentaasteran Series . In: Chemical Reports . tape 121 , no. 2 , February 1988, p. 323 , doi : 10.1002 / cber.19881210219 .
  13. ↑ Axel Bader, Klaus Ebel, Hans Musso, Norbert Skuballa: Asterane, XXI. Further attempts to synthesize pentaasterane . In: Chemical Reports . tape 121 , no. 2 , February 1988, p. 327 , doi : 10.1002 / cber.19881210220 .