Regioselective Synthesis of Allyltrimethylsilanes from Allylic Halides and Allylic Sulfonates. Application to the Synthesis of 2,3-Bis(trimethylsilyl)alk-1-enes

Article abstract of DOI:10.1021/jo00196a002

The preparation of allyltrimethylsilanes by regioselective pathways is described.Treatment of (E)-1-chloro-2-alkenes with a reagent prepared from 1 equiv each of trimethylsilyllithium and copper(I) iodide in hexamethylphosphoramide to presumably form a (trimethylsilyl)copper reagent affords 3-(trimethylsilyl)-1-alkenes in good to excellent yields with a high regioselectivity.Treatment of these same 1-chloro-2-alkenes with (trimethylsilyl)lithium alone without added copper(I) iodide yields only (E)-1-(trimethylsilyl)-2-alkenes.A single allylic halide thus yields two regioisomeric allyltrimethylsilanes by proper choice of reaction conditions.The reaction of a variety of allylic sulfonates with (trimethylsilyl)copper has also been investigated.The mesylates of 2 deg and 3 deg allylic alcohols yield mixtures of isomeric allyltrimethylsilanes in which the 1-(trimethylsilyl)-2-alkenes predominate.With geraniol, the mesylate was prepared in situ and allowed to react with (trimethylsilyl)copper to afford two isomeric allyltrimethylsilanes in which the 3-(trimethylsilyl)-1-alkene predominates.Finally, these reactions have also been used to prepare a variety of 2,3-bis(trimethylsilyl)alk-1-enes, a class of unsaturated organosilanes which has received little attention in the literature.