Synthesis and Cycloaddition Reactions of 1-Azido-1,1,2,2-tetrafluoroethane

Abstract

A new fluorinated azidoethane1-azido-1,1,2,2-tetrafluoroethanewas prepared in quantitative yield by the addition of an azide anion to tetrafluoroethylene in a protic medium. The title azide was shown to be thermally stable and insensitive to impact. Copper­(I)-catalyzed [3 + 2] cycloaddition with alkynes afforded 4-substituted N-tetrafluoroethyl-1,2,3-triazoles which underwent rhodium­(II)-catalyzed transannulation with nitriles to novel N-tetrafluoroethylimidazoles or the reaction with triflic acid to enamido triflates. [3 + 2] Cycloaddition of the title azide with primary amines afforded novel 5-difluoromethyl tetrazoles.

Access to N-Difluoromethyl Amides, (Thio)Carbamates, Ureas, and Formamides

“…Indeed, the single reported synthesis to acyclic N -difluoromethyl amides relies on the unselective functionalization of low-functionality N -aromatic amides with difluorocarbene under highly basic conditions (in ≤30% yield in a mixture with O-difluoromethylation). 18 The current synthetic repertoire to N -CF 2 H compounds only provides efficient access to selected N -difluoromethylated heterocycles, 19 such as triazoles, 20 indoles, 21 2-pyridones 22a or (benz)imidazoles, 22b tosyl-protected N -CF 2 H amines, 23 tosyl-protected hydrazones, 24 or ammonium salts. 25 Any attempt to remove the tosyl group in Ts-protected N -CF 2 H amines to the corresponding free N -difluoromethyl amines [i.e., H- N (CF 2 H)R] has so far remained unsuccessful, however, owing to their instability.…”