4-(Dimethylamino)Pyridinium Azide in Protic Ionic Liquid Media as a Stable Equivalent of Hydrazoic Acid

We report a procedure for the multigram synthesis of 4-(dimethylamino)pyridinium azide, a stable, non-explosive, low-hygroscopic source of azide ion soluble in both protic and aprotic organic solvents. In protic ionic liquid media this reagent was shown to serve as a safer equivalent of toxic and unstable hydrazoic acid. The synthetic utility of this system was demonstrated using donor-acceptor cyclopropane ring opening as a model process. General procedures furnishing a variety of dialkyl (2-azido-2-arylethyl)malonates or 4-azido-4-arylbutyrates, depending on the protic ionic liquid applied, were elaborated. The conversion times for studied donor-acceptor cyclopropanes were established providing the relative reactivity sequence. The application of 4-(dimethylamino)pyridinium azide for a conventional nucleophilic substitution, oxirane ring opening, (3+2)-cycloaddition to (thio)cyano group as well as their combinations realized as telescopic synthesis was also demonstrated. © 2022 Wiley-VCH GmbH.