Phosphine Induced Dimerization of Propargyl Alcohols Leading to Allyl Propargyl Ethers.

A facile method for synthesizing allyl propargyl ethers (APEs) was developed based on the dimerization of propargyl alcohols. The reaction proceeded via an oxaphosphetane intermediate, which was generated without the use of a strong base, thus making this process a pseudo-Wittig reaction under mild reaction conditions. A wide variety of functional groups, including formyl and pyridyl groups were tolerated, thus yielding the corresponding functionalized APEs, which are otherwise not readily prepared via conventional methods. Moreover, a cross-reaction was found to occur when the reaction was conducted in the presence of alcohols that were more acidic than propargyl alcohol, which suggests that the proton transfer from the intermediately formed betaine to the second alcohol is crucial for undergoing the dimerization.