Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Treatment of the unsaturated ketone 6 with phenylhydrazine fails to afford the unsaturated phenylhydrazone 3 but gives the tricyclic phenylhydrazoketone exo-8, which is oxidised with iron(III) chloride to yield the phenylazoketone exo-9. The configuration of exo-9 is elucidated with the help of an X-ray diffraction analysis. The unsaturated phenylazo compound 14 is obtained from Meerwein's diketone 10 in two ways. Iodination of the phenylhydrazone 11 in the presence of pyridine followed by elimination of pyridinium iodide from the bispyridinium salt 13 with aqueous sodium hydroxide in dimethyl sulphoxide furnishes 14 in low yield. A somewhat better yield is more conveniently achieved when the dibromodiketones exo,exo- and exo,endo-12 are allowed to react with phenylhydrazine in the presence of pyridine. Bromination of 14 with N-bromosuccinimide in cyclohexane as solvent affords the labile dibromide 15. Both reagents employed, viz. the zinc/copper couple in refluxing tetrahydrofuran and butyllithium at low temperature, fail to convert 15 into the hoped-for bis(phenylazo)barbaralane 1 but instead give rise to the formation of the isomer 17, either by cyclisation of the intermediate anion 16 or by rearrangement of 1.
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