Synthesis of polyfluoroalkyl cyclobutenes from 3-aza-1,5-enynes via an aza-Claisen rearrangement/cyclization cascade.

A facile synthetic route to access polyfluoroalkyl functionalized cyclobutenes bearing an exo cyclic double bond from 3-aza-1,5-enynes is reported. The reaction proceeds via a thermal aza-Claisen rearrangement to give an allene-imine intermediate; subsequent cyclization affords the cyclobutene core. The kinetics of the transformation of starting material and the intermediate was studied by (1)H NMR spectroscopy, where a consecutive reaction was revealed.