POLYLITHIUMORGANIC COMPOUNDS, 24 - THE REACTION OF SUBSTITUTED VINYLSILANES WITH LITHIUM METAL

Vinylsilanes are known to react with lithium metal to form either 1,2- dilithioethanes by reduction or 1,4-dilithiobutanes by reductive dimer ization. The reaction of the substituted vinylsilanes 3, (Z)-13b, 17b, c, 42b, c, 44, and 51 with lithium has been investigated. Depending o n the substituents on the vinylsilane and the solvent employed, severa l new reaction pathways are observed, which have been proved by indepe ndent syntheses of the reactive intermediates (E)-14b, 18d, and 25-27. Thus, besides the known elimination of lithium hydride, either a 1,4- proton shift of 25 to 26 or a Grovenstein-Zimmerman rearrangement of 4 5 to 47 can occur as follow-up reactions. Furthermore, two different t ypes of dimerization of the silyl-substituted vinyllithium compounds h ave been identified, Either the vinyllithium compound 18d adds to the starting vinylsilane leading to the monolithiumorganic species 41, or Lithium metal catalyzed dimerization to the 1,4-dilithio-2-butene deri vative 49 takes place, which is without precedence.