Mechanochemical Desymmetrization of Unbiased Bis- and Tris-alkynes to Access 3,5-Isoxazoles-Alkyne Adducts and Unsymmetrical Bis-3,5-isoxazoles

A mechanochemical desymmetrization of symmetrical bis- and tris-alkynes via a controlled 1,3-dipolar cycloaddition reaction with nitrile oxide dipoles has been developed. This convenient, efficient, and simple protocol allows access to 3,5-isoxazole-alkyne adducts from easily prepared or commercially available symmetrical bis- and tris-alkynes in moderate to excellent yield. The synthetic utility of 3,5-isoxazole-alkyne was demonstrated by developing a route to access β-ketoenamine-alkyne derivatives and the synthesis of unsymmetrical bis-3,5-isoxazoles products in good to excellent yields.