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Comparison of Carbon−Silicon Hyperconjugation at the 2- and 4-Positions of the N-Methylpyridinium Cation

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posted on 2005-03-18, 00:00 authored by Kathryn Hassall, Sofia Lobachevsky, Jonathan M. White
N-Methyl-2-trialkylsilylmethylpyridinium cations 6ac and 4-trialkylsilylmethylpyridinium cations 5ac were prepared and investigated using 29Si and 13C NMR and single-crystal X-ray crystallography. Systematic differences in the 29Si chemical shifts and 29Si−13C one-bond coupling constants for these cations suggested that the Si−CH2 bond interacts more strongly at the 2-position of the electron-deficient pyridinium ring than at the 4-position. This result is supported by the X-ray structures of the pyridinium cations 5b and 6b.

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