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 1H NMR spectroscopy, where a consecutive reaction was revealed.