Catalyzed [2+2]-Cycloaddition Reactions of Hexafluoroisopropyl 4-Chloro-2-oxobut-3-ynoate with Simple Alkenes

It is shown for the first time that the [2+2]-cycloaddition reactions of hexafluoroisopropyl 4-chloro-2-oxobut-3-ynoate with simple alkenes, proceeding sluggishly in an excess of alkenes or in usual solvents, are strongly improved by hexafluoroisopropanol (HFIP). The yields of the target products also increase compared to the conventional methods. A general protocol for performing such transformations has been developed.