Background: Propargylic derivatives are important reagents and building blocks in organic
synthesis. They can be obtained starting with propargylic alcohols or their protected forms. The actual
methods rely on the use of acidic or metal-catalyzed approachs. These efficient methods however need
to use solvents and metals, that are sometimes toxic or expensive. Ways to prepare those derivatives
without metals or solvents can thus be an interesting alternative.
Methods: During our work on propargyl carbonates, we found out that reflux in an alcoholic solvent was
producing in part the corresponding ether. In this paper we present the study of reaction conditions under
microwaves in order to accelerate them. The reaction conditions were optimized using a model substrate
and alcohol in order to find the best ratio, temperature and power mode to obtain propargylic ethers form
their methyl carbonate. The conditions were then applied to different propargylic derivatives to evaluate
the scope of this reaction.
Results: The reaction was applied to different propargyl methyl carbonates and alcohols to evaluate the
scope of the reaction. Propargyl ethers can be synthesized from carbonates bearing an aromatic ring and alcohols
in good yields, by irradiating them together by microwaves. The limitations include hindered alcohols
and propargyl carbonates without aromatic rings as substituents on the carbon atom bearing the carbonate.
Conclusion: During this study, we were able to find out conditions to prepare propargylic ethers from
propargyl carbonate and the alcohol, as a solvent and reagent. The ethers can be easily and readily prepared
in 0.5 h by microwave irradiation. The reaction can be applied to derivatives bearing groups that
can stabilize the carbocationic intermediate proposed in the mechanism. Even if some limitations were
encountered, the reaction gives the opportunity to prepare propargylic ethers from their carbonates
without the use of acidic- or metal-catalyzed conditions, or solvent other than the reagents, in a simple
and straightforward approach.