Formation of organosilicon compounds 117: C-brominated 1,3,5-trisilacyclohexanes and their reactions with BuLi

Article abstract of DOI:10.1139/v00-035

The photobromination of 1,1,3,3,5,5-hexamethyl-1,3,5-trisilacyclohexane (1) almost exclusively attacks CH₂ groups and results in 2,2-dibromo-trisilacyclohexane (2) as well as 2,2,4,4-tetrabromo-trisilacyclohexane (3) in high yields. Starting from a mixture of C-brominated trisilacyclohexanes the isomeric 2,2,9-tribromo-1,3,3,5,5,8,8,10,10,13,13-undecamethyl-1,3,5,8,10,13- hexasilabicyclo[7.2.2]tridec-6-yne (6) had been obtained in very low yield in an attempt to establish a preparative route to adamantanes with a C₄Si₆ skeleton, i.e., with C bridgeheads and SiR₂ bridges. By ICl-cleavage of a Si - methyl bond in 2 and subsequent substitution with Br₃CLi, the trisilacyclohexane 4 with functional groups in opposite positions of the ring can be obtained. Linking the step-by-step synthesized Cl-Me₂Si-C≡C-SiMe₂-CH₂-SiMe ₂-Ph to the CBr₃ group of 4 results after HBr-cleavage of the Si - Ph bond in (ω-bromo-octynyl)-trisilacyclohexane (12). A ring closure of 12 would result in an isomeric hexasilabicyclo[7.2.2]tridec-6-yne. The compounds were characterized by ¹H, ¹³C, and ²⁹Si NMR spectra. Additionally, the molecular structures of 4 and 6 were confirmed by X-ray single crystal investigations.