A Study of Essentially Free Carbocations Derived via Diazonium and Oxo Diazonium Ions in the Liquid Phase
Nitrogen- and nitrous oxide-separated ion pairs containing 4-substituted benzyl cations and carboxylate or tosylate anions were prepared by thermolysis of N-nitroso- and N-nitroamides, acidification of phenyldiazomethane, and nitrosation of N-benzyl-O-benzoylhydroxylamine. The cations were generated...
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Published in | Journal of organic chemistry Vol. 64; no. 16; pp. 5966 - 5978 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
WASHINGTON
American Chemical Society
06.08.1999
Amer Chemical Soc |
Subjects | |
Online Access | Get full text |
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Summary: | Nitrogen- and nitrous oxide-separated ion pairs containing 4-substituted benzyl cations and carboxylate or tosylate anions were prepared by thermolysis of N-nitroso- and N-nitroamides, acidification of phenyldiazomethane, and nitrosation of N-benzyl-O-benzoylhydroxylamine. The cations were generated in benzene/toluene and benzene/anisole mixtures and were found to partition between the counterion and the solvent and between the aromatic cosolvent and benzene. A familial relationship among the methods was observed. As the cation became more reactive, the yield of solvent-derived products (SDPs) rose and the ratio of rate constants for its reaction with toluene versus benzene, k T/k B, fell. The yield of SDP also rose as the temperature was decreased and as N2 was replaced by N2O; however, k T/k B remained unchanged. Inert diluents had no effect on k T/k B but decreased hydrocarbon yield by 40% on 2-fold dilution. In the presence of reactive diluents that are converted into secondary alkylating agents, both the % hydrocarbon and k T/k B rose. These results are interpreted in terms of the intermediacy of inert-molecule-separated ion pairs (IMSIPs) in deamination. The cation reacted with benzoates and tosylates not only at the oxygens but also at the ipso carbon; subsequent decarboxylation and desulfonylation, respectively, led to diphenylmethanes. The ester/SDP ratio is introduced as a new measure of carbocation reactivity. |
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Bibliography: | ark:/67375/TPS-FG5GV5ZN-S istex:442D1AF7562C2AA215E372BE74C0DE0B0891EC36 |
ISSN: | 0022-3263 1520-6904 |
DOI: | 10.1021/jo990494m |