ISSN:
0009-2940
Keywords:
Homoaromaticity in carbanions
;
Bicyclo[3.2.1]oct-3-en-2-yl anions, phenyl-substituted
;
Tricyclo[3.3.1.02,4]non-7-en-6-ylpotassium, 6-phenyl
;
Exchange of Li+ for NMe4+
;
7Li-NMR spectra
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Inductive Effect, Negative Hyperconjugation, and Gegenion do not Cause the Unusual Properties of the Bicyclo[3.2.1]octa-3,6-dien-2-yl Anion. An NMR Study with Phenyl-Substituted ModelsThe 13C-NMR spectra of the phenyl-substituted bicyclo[3.2.1]oct-3-en-2-yl anions of 41-K and 61-Li show that in the corresponding dienyl anions of 31-K and 51-Li not only C-6,7 have unusual chemical shifts but also C-2,3,4. The values of the phenyl groups prove the larger negative charge in the allyl system of 41-K and 61-Li as compared to that of 31-K and 51-Li, respectively. Thus, the C6-C7 π bond in 31-K and 51-Li causes the reduction of the negative charge in the allyl subunit. Different from the effect of the C6-C7 π bond in 31-K, the anellated three-membered ring in the tricyclo[3.3.1.02,4]1-nonenyl anion of 71-K has no influence on the chemical shifts of the phenyl-substituted allyl anion moiety. Experiments aimed at the exchange of the metal cations of 31-K, 51-Li, and 61-Li for a tetramethylammonium ion were successful only with 51-Li. The NMR data of 51-Li and 51-NMe4 are virtually identical. In the case of 31-Li and 61-Li, the treatment with tetramethyl-ammonium chloride caused an SN2 process with formation of the methylbicyclooctadienes 8a and 10, respectively. Also, 51-Li underwent this reaction, however so slow that significant concentrations of 51-NMe4 could be observed in solution. 7Li-NMR spectra were taken from 51-Li, 61-Li, and the solution containing 51-NMe4.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260233
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