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Preparation of 1‑Azido-2-Bromo-1,1,2,2-Tetrafluoroethane and Its Use in the Synthesis of N‑Fluoroalkylated Nitrogen Heterocycles

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journal contribution
posted on 19.08.2020, 17:04 by David Tichý, Vojtěch Košt́ál, Vladimir Motornov, Iveta Klimánková, Petr Beier
A straightforward synthesis of 1-azido-2-bromo-1,1,2,2-tetrafluoroethane on a multigram scale from 1,2-dibromotetrafluoroethane and sodium azide in a novel process initiated by organomagnesium compounds (i-PrMgCl·LiCl, turbo Grignard) is reported. Synthetic utility of the title azide in the preparation of N-tetrafluoroethylated and N-difluoromethylated five-membered nitrogen heterocycles was demonstrated with azide-alkyne cycloaddition to N-bromotetrafluoroethyl 1,2,3-triazoles, subsequent reduction to N-tetrafluoroethyl triazoles, rhodium-catalyzed transannulation with nitriles to N-tetrafluoroethylated imidazoles and rhodium-catalyzed ring-opening, and cyclization to N-difluoromethylated oxazoles and thiazoles.