Barbaralan

Structural formula
General
Surname	Barbaralan
other names	Tricyclo [3.3.1.0 2.8 ] nona-3,6-diene
Molecular formula	C 9 H 10
Brief description	light-sensitive, unpleasant smelling, colorless crystals
External identifiers / databases
CAS number 14693-11-9 PubChem 139807 Wikidata Q69580302
properties
Molar mass	118.18 g mol −1
Melting point	46 ° C
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Barbary Alan is an unsaturated polycyclic C ₉ H ₁₀ - hydrocarbon in which a 3,4-homotropilidene moiety with a methyl group is bridged.

presentation

The first synthesis of Barbaralan was carried out in 1967 by Hans Musso et al. described. Starting from triasteranone 1 , reaction with tosylhydrazide 2 gives tosylhydrazone 3 , which is converted to barbaralan 5 via the intermediate cation 4 on heating with sodium glycolate with elimination of nitrogen and a tosyl anion in the sense of a Bamford-Stevens reaction .

Synthesis of barbaralan starting from triasteranone

One of William von Eggers Doering et al. The alternative synthetic route developed starts from cycloheptatriene 1 . First a nitrile group is introduced via the tropylium cation , the methanolysis of which leads to the ester 3 . This is followed by hydrolysis to carboxylic acid 4 and conversion into acid chloride 5 with thionyl chloride . Reaction with diazomethane gives compound 6 . In the presence of copper, a carbene is obtained with elimination of nitrogen , which reacts intramolecularly to form a cyclopropane ring with the middle double bond of the cycloheptatriene ring. You get the Barbaralon 7 . The reduction of barbaralone with lithium aluminum hydride gives the alcohol 8 , which, after conversion with methanesulfonyl chloride into the mesylate compound 9 , can be reduced with lithium aluminum hydride to barbaralan 10 .

Synthesis of barbaralan starting from cycloheptatriene

The compounds Barbaralon and Barbaralan were named after the chemist Barbara M. Ferrier from W. v. E. Doering named.

properties

As a bridged 3,4-homotropilid, Barbaralan, like Bullvalene or Semibullvalene, is one of the molecules with a “fluctuating structure”. Due to the degenerate Cope rearrangement , two structurally identical valence isomers are in rapid equilibrium:

Degenerate Cope rearrangement
at the Barbaralan

Since the cisoid conformation of the homotropilid unit is fixed by the methylene bridge , the activation energy of the Cope rearrangement is lower than that of the 3,8-homotropilid and, like this, the NMR spectrum is temperature-dependent. At −100 ° C the NMR spectrum shows a pronounced fine structure for the signals of the six different hydrogen atom groups of the molecule. The four mixed signals of the two valence isomers are obtained at 25 ° C.

Individual evidence

1. ↑ ^{a b c} U. Biethan, H. Klusacek, H. Musso: Rearrangements in the Triasterane system . In: Angewandte Chemie . tape 79 , no. 3 , February 7, 1967, p. 152 , doi : 10.1002 / anie.19670790315 .
2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
3. ↑ ^{a b} W. von E. Doering, BM Ferrier, ET Fossel, JH Hartenstein, M. Jones, G. Klumpp, RM Rubin, M. Saunders: A rational synthesis of bullvalenes barbarian alone and derivatives; bullvalone . In: Tetrahedron . tape 23 , no. January 10 , 1967, p. 3943 , doi : 10.1016 / S0040-4020 (01) 97904-9 .
4. ↑ Ulrike Weier: Influences of substitutes on the Cope rearrangement in the Barbaralan . Dissertation, University of Karlsruhe (TH). Karlsruhe 1987.