ISSN:
0009-2940
Keywords:
Semibullvalenes
;
[n.3.3] Propellanes, derivatives of
;
Vinyl sulphides and sulphones
;
Bromination, allylic
;
Debromination
;
Zinc-copper couple
;
Cope rearrangement in the solid state
;
Valence tautomers, non-equivalent
;
Equilibrium constants from atomic distances
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The bicyclo[3.3.0]octanediones 4 and 9a, b and the [n.3.3]-propellanediones 9c, d, f, h react with thiophenol in the presence of titanium(IV) chloride and triethylamine to afford high yields of the vinyl sulphides 5 and mixtures of the vinyl sulphides 10/11. Sodium perborate oxidizes the vinyl sulphides 5 and 10/11 to the corresponding vinyl sulphones 6 and 12/13. N-Bromosuccinimide converts 6 into the dibromodisulfones 7. The exo,exo configuration of 7b is established by X-ray crystallography. The mixtures of disulphones 12/13 are brominated by N-bromosuccinimide to yield complex mixtures of uncharacterized dibromodisulphones 14. Debromination of the dibromodisulphones 7, and the mixtures of 14 as well, by the zinc-copper couple results in the formation of crystalline semibullvalenes 8 and 15 in moderate to high yields. - X-ray diffraction analyses of 8a, b and 15a-d reveal large variations of the apparent atomic distances in the cyclopropane rings (C2-C8) and at the open ends of the molecules (C4…C6). This result is interpreted in terms of equilibrating, non-degenerate valence tautomers resulting in averaged atomic distances. The equilibrium constants are calculated from the atomic distances on the basis of a limiting value of 157.8 pm for the C2-C8 bonds of the non-rearranging valence tautomers. The results are compared to those obtained from X-ray diffraction analyses of other substituted semibullvalenes. The lifting of the degeneracy of semibullvalenes in the solid state is attributed to subtle intermolecular interactions.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19921250430