Bildung siliciumorganischer Verbindungen. 90. Synthese C-verbrückter Carbosilane

Formation of Organosilicon Compounds. 90. Synthesis of C-linked Carbosilanes n-buLi metallates 1 to give 2 , which with phme₂SiCl (ph = C₆H_5, me = CH₃) forms 3 . This compound yields 4 with Br₂. Lithiation of 3 yields 5 which for sterical reasons cannot be substituted with phme₂SiCl. The spiro compounds 10 and 11 are available by treating 2 with (Brme₂Si)₂CH₂ or (Brme₂SiCH₂)₂-Sime₂, resp. By means of n-buLi the CBr group in 4 can be metallated. On warming to 20°C the lithiated compound eliminates LiBr via an highly reactive intermediate to form 12 , 12 shows an extraordinary stability of the Si? C fourmembered ring against HBr or Br₂