Synthesis of Trisubstituted Oxazoles via Aryne Induced [2,3] Sigmatropic Rearrangement–Annulation Cascade

Abstract

A transition-metal-free, 2,3 sigmatropic rearrangement-annulation cascade of 2-substituted thio/amino acetonitriles with arynes allowing the synthesis of 2,4,5-trisubstituted oxazoles under mild conditions has been demonstrated. The key sulfur/nitrogen ylides were generated by the initial S/N arylation followed by proton transfer, which was followed by the selective 2,3 sigmatropic rearrangement involving the -CN moiety and a subsequent annulation to afford the desired products in reasonable yields.