Synthesis of stable 2-silanaphthalenes and their aromaticity

被引:105
作者
Wakita, K
Tokitoh, N
Okazaki, R
Nagase, S
Schleyer, PV
Jiao, HJ
机构
[1] Univ Tokyo, Grad Sch Sci, Dept Chem, Bunkyo Ku, Tokyo 1130033, Japan
[2] Tokyo Metropolitan Univ, Grad Sch Sci, Dept Chem, Hachioji, Tokyo 1920397, Japan
[3] Univ Georgia, Ctr Computat Quantum Chem, Athens, GA 30602 USA
[4] Univ Erlangen Nurnberg, Inst Organ Chem, Comp Chem Ctr, D-91054 Erlangen, Germany
关键词
D O I
10.1021/ja992024f
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Stable neutral silaaromatic compounds, 2-silanaphthalenes (1a; R = Tbt, 1b; R = Bbt), were synthesized by taking advantage of extremely bulky and efficient steric protection groups, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) and 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methy]phenyl (Bbt). 2-Silanaphthalenes 1a,b were isolated as colorless crystalline compounds, and the structure of Tbt-substituted la was determined by X-ray crystallographic analysis. All H-1, C-13, and Si-29 NMR signals of the silanaphthalene ring of 1 were in good agreement with those calculated; dowmfield-shifted H-1 signals indicating aromatization were observed. Refined NICS (nucleus-independent chemical shift) calculations which separate the sigma and pi contributions revealed the presence of comparably large ring current effects in the two rings of 2-silanaphthalene. The aromatic stabilization energies (ASEs) of 1-, 2-, and 9-silanaphthalenes, computed by a novel isomerization method, are almost the same as naphthalene. UV-vis and Raman spectra, and the computed (B3LYP/6-311 +G(d,p)) structure of 2-silanaphthalene were similar to those of naphthalene, although characteristic changes resulting from the replacement of carbon to silicon were observed. 2-Silanaphthalene la is still highly reactive due to its polarized Si=C moiety, but was relatively stable toward air in the solid stale and showed no complex formation with TNF in solution. Considering all experimental and theoretical results, the 2-silanaphthalenes were concluded to have considerable aromatic character, closely approaching that of naphthalene itself.
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页码:11336 / 11344
页数:9
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