The Si-Si σ bond directly attached an aromatic ring can be conjugated by the σ-π interaction. The conjugation effectively elongates fluorescence and absorbance wavelength, and therefore, attention has been focused on the σ-π conjugation to use if for the development of specific organic electro devices, the electronic properties were mainly evaluated. On the other hand, the effect of σ-π conjugation derived from Si-Si bond in the transition state in reactions has not been detected exactly. Tris(trimethylsilyl)silyl aromatic analogue often easily decompose during the reactions, and the reaction pathway is rather difficult to estimate. In this study, we prepared a new pyridine analog, which is substituted by a tris(trimethylsilyl)silyl group at the C4 position. To estimate its nucleophilicity comparing with other 4-substituted pyridine analogues, we analyzed their SN2 reaction (Menschutkin reaction) with methyl iodide as an electrophile by measuring NMR spectra. The reaction rate of the silylated pyridine was similar to that of 4-picoline, and significantly slower than that of 4-dimethylaminopyridine. These results suggested that, although the Si-Si σ-π conjugation generally shifts the electrostatic state of the aromatic ring, it is ineffectual to the nucleophilicity of pyridines. Spectroscopic properties of compounds are also presented.

Effect of σ-π conjugation between Si-Si bond and pyridine ring in tris(trimethylsilyl)silylpyridine on its spectroscopic property and SN2 reaction with methyl iodide

251st National Meeting (2016)

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