Intramolecular Cyclization of N -Propargylic Amides without Transition-Metal Catalysis for Synthesis of Fluoroalkylated Oxazoles: Using Carboxylic Acid Anhydrides as the Fluoroalkyl Source

Abstract

Synthesis of 2-fluoroalkylated oxazoles was developed by transition-metal-free intramolecular cyclization of N-propargylic amides, which are prepared from propargylic amines employing a small excess of commercially available fluorocarboxylic acid anhydrides as fluoroalkyl sources, under basic conditions. Oxazoles bearing trifluoromethyl, pentafluoroethyl, or heptafluoropropyl group at the C-2 position and the functional groups on the C-4 and/or C-5 positions are provided in moderate to high yields by controlling the reaction conditions.