(E)- and (Z)-(l-Iodo-l-alkenyl)silanes. Their Preparation and Their Conversion into (E)- and (Z)-(l-Lithio-l-alkenyl)silanes

Abstract

(Z) - (1 -Iodo- 1-alkenyl) trimethylsilanes can be conveniently obtained by isomerization of the readily available E isomers through the intermediacy of (l-lithioalkenyl)silanes formed by addition of catalytic amounts of tert-butyllithium. Reaction of (E)- and (Z)-(l-iodoalkenyl)silanes with 2.1 equiv of tert-butyllithium produces the (E)- and (Z)-(l-lithio-l-alkenyl)silanes. These synthetically important alkenyllithiums have been found to be configurationally stable at -70 °C. However, they isomerize at higher temperatures, reaching an E/Z equilibrium distribution at 0 °C of 86:14 (±5%) irrespective of the size of the β-alkyl substituent. © 1981, American Chemical Society. All rights reserved.