Reductive Cleavage of Propargylic Ethers with Alkali Metal: Application to the Synthesis of Allenylboronates

Treatment of propargylic ethers with sodium dispersion in the presence of lithium iodide results in the generation of the corresponding carbanion species via cleavage of the propargylic C–O bond. The anionic species react with trimethoxyborane to yield the allenylboronates including highly substituted ones that are difficult to synthesize.