Synthesis of 4‑Silacyclohexan-1-ones and (4-Silacyclohexan-1-yl)amines Containing the Silicon Protecting Groups MOP (4-Methoxyphenyl), DMOP (2,4-Dimethoxyphenyl), or TMOP (2,4,6-Trimethoxyphenyl): Versatile Si- and C‑Functional Building Blocks for Synthesis

Abstract

The 4-silacyclohexanones <b>1</b>–<b>6</b> were prepared in convenient multistep syntheses, starting from MeSi­(OMe)₃ and PhSi­(OMe)₃, respectively. Cleavage of the 4-methoxyphenyl (MOP), 2,6-dimethoxyphenyl (DMOP), and 2,4,6-trimethoxyphenyl (TMOP) protecting groups of <b>4</b>–<b>6</b> by treatment with HCl/Et₂O in CH₂Cl₂ at 20 °C gives the 4-chloro-4-silacyclohexanone <b>13</b>. Reductive amination of <b>1</b>–<b>6</b> with NH₃ or <i>i</i>-PrNH₂ yields the respective (4-silacyclohexan-1-yl)­amines <b>7</b>–<b>12</b>. Compounds <b>1</b>–<b>12</b> and all new precursors synthesized were characterized by elemental analyses (C, H, N) or mass spectrometric investigations (ESI-HRMS) and by NMR spectroscopic studies (¹H, ¹³C, ²⁹Si). Compounds <b>1</b>, <b>3</b>, <b>5</b>, and <b>6</b> and the precursors (MeO)₂SiPh­(TMOP) (<b>21</b>) and (CH₂CH)₂SiPh­(TMOP) (<b>27</b>) were additionally characterized by single-crystal X-ray diffraction. Compounds <b>1</b>–<b>12</b> with their Si- and C-functional groups represent versatile building blocks for synthesis