Synthesis of Kinetically Stabilized 1-Silanaphthalenes and Their Properties

The first kinetically stabilized 1-silanaphthalenes bearing a 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) group or a 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) group were synthesized from the corresponding overcrowded bromosilanes by dehydrobromination using LDA (lithium diisopropylamide) in THF at -40 C, respectively. The structures of 1-silanaphthalenes were confirmed by 1 H, 1 3 C, and 2 9 Si NMR, UV-vis, Raman, and high-resolution mass spectroscopic analyses. These results and the NICS calculations indicated high aromaticity of the 1-silanaphthalenes. In spite of such high aromaticity, Tbt-substituted 1-silanaphthalene is thermally unstable and undergoes gradual dimerization in C 6 D 6 solution to give the corresponding [4 + 2] dimer. By contrast, 1-silanaphthalene bearing a Bbt group on the Si atom was thermally stable even on heating in C 6 D 6 at 120 °C. Tbt-substituted 1-silanaphthalene has high reactivity toward addition reactions at both 1,2- and 1,4-positions, giving the corresponding adducts in the reactions with H 2 O, MeOH, mesitonitrile oxide, benzophenone, and elemental chalcogens. Tbt-substituted 1-silanaphthalene underwent 1,4-addition reaction with CCl 4 to give cis- and trans-adducts having a Cl atom on the Si atom and a CCl 3 group at the 4-position.