Stereochemical aspect of the electroreduction of activated cyclens— III. Study of 2,3-dicarboxy (and dicarbethoxy) indens' reduction mechanism; stereochemistry, kinetic study of the double bond migration
✍ Scribed by R. Hazard; J. Sarrazin; A. Tallec
- Publisher
- Elsevier Science
- Year
- 1980
- Tongue
- English
- Weight
- 557 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0013-4686
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✦ Synopsis
The two-electron reduction mechanism of the title compounds has been established by means of polarographic measurements showing, on the other hand, an equilibrium between 2,3-and 1,2-disubstituted forms. Kinetic study of this equilibrium allows the knowledge of the first acidity constants of the two diacidic isomers.
Electrolysis results confirm that, for this series of compounds, the stereochemistry of the obtained dihydrogcnated cyclane depends fundamentally on the nature of the diffusing species:
(i) when rhe latter is a monocarboxylate (case of the diacid, pK, < pH < pK,), a very small amount (5 per cent) of cis cyclan is obtained. (ii) in the case of a dicarboxylate ion (diacid, pH > pK,), the yield of the cis isomer is about 15 per cent.
(iii) if a molecule diffuses, the yield of cis cyclan is maximum but the protonation of the final carbanion interferes kinetically.