Hydrogen Migration and Lithium Iodide α-Elimination in 1-Iodo-1-lithioethene. Concerted vs Stepwise Mechanism

Abstract

1-Iodo-1-lithioethene is prepared from 1-iodoethene and LDA in THF. The lithiated derivative can be trapped by electrophiles, but it readily decomposes to acetylene; the decomposition process cannot be analyzed by experimental techniques. Ab initio calculations indicate that 1-iodo-1-lithioethene should be a monomer in a THF solution. Furthermore, hydrogen migration and lithium iodide α-elimination procedures should occur through a concerted mechanism. The activation barrier for the cis and trans hydrogen migration should be almost identical.