ISSN:
0170-2041
Keywords:
Bicyclo[3.3.1]nonane-2,6-dione, brominated derivatives of
;
Bromination of ketones by copper(II) bromide
;
Dehydrobromination, 1,2- and transannular
;
Noradamantane, derivative of
;
Conformation of bicyclo[3.3.1]-nonane-2,6-dione and derivatives
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Conformation and Bromination of Bicyclo[3.3.1]nonane-2,6-dione and Dehydrobromination of the Bromo Ketones. - Improved Synthesis of Bicyclo[3.3.1]nona-3,7-diene-2,6-dioneBromination by copper(II) bromide of bicyclo[3.3.1]nonane-2,6-dione (1) affords the epimeric α-bromo diketones exo-and endo-5 and, eventually, the α, α′-dibromo diketones exo- and endo-7 (3:7) in high yield. Dehydrobromination of the mixtures of bromo diketones by calcium carbonate in dimethylacetamide yields the unsaturated diketones 6 (30%) and 2 (72%), respectively. Bromination of 1 by molecular bromine is less selective and furnishes mixtures of brominated diketones consisting of exo- and endo-7, 8 and the tetrabromo diketone 10. An excess of bromine yields pure 10. - The ethylene acetal 12 is brominated by pyridinium perbromide to produce the α,α′-dibromo acetal 13 which is very reluctant towards 1,2-dehydrobromination by potassium tert-butoxide. Thus, with an excess of potassium tert-butoxide in tetrahydrofuran, 1,2-dehydrobromination is achieved only on one side to afford 14. In contrast, potassium tert-butoxide in dimethyl sulphoxide induces a transannular dehydrobromination leading to the diacetal 15 of 3-bromonoradamantane-2,6-dione. - The conformations of 1,10, and 13 in the solid state are determined by X-ray diffraction analyses. From torsional angles, vicinal proton coupling constants are calculated with the aid of the Karplus equation and compared to those determined from solutions by high-field NMR spectroscopy. The reasonable agreement provides the basis for the assessment of the configuration and conformation for exo- and endo-7.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199419940203
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