Marriage of Peroxides and Nitrogen Heterocycles: Selective Three-Component Assembly, Peroxide-Preserving Rearrangement, and Stereoelectronic Source of Unusual Stability of Bridged Azaozonides

Stable bridged azaozonides can be selectively assembled via a catalyst-free three-component condensation of 1,5-diketones, hydrogen peroxide, and an NH-group source such as aqueous ammonia or ammonium salts. This procedure is scalable and can produce gram quantities of bicyclic stereochemically rich heterocycles. The new azaozonides are thermally stable and can be stored at room temperature for several months without decomposition and for at least 1 year at -10 degrees C. The chemical stability of azaozonides was explored for their subsequent selective transformations including the first example of an aminoperoxide rearrangement that preserves the peroxide group. The amino group in aminoperoxides has remarkably low nucleophilicity and does not participate in the usual amine alkylation and acylation reactions. These observations and the 15 pK(a) units decrease in basicity in comparison with a typical dialkyl amine are attributed to the strong hyperconjugative n(N)->sigma*(C-O) interaction with the two antiperiplanar C-O bonds. Due to the weakness of the complementary n(O)->sigma*(C-N) donation from the peroxide oxygens (a consequence of inverse alpha-effect), this interaction depletes electron density from the NH moiety, protects it from oxidation, and makes it similar in properties to an amide.

Automated summary

Stable bridged azaozonides can be selectively assembled through a catalyst-free three-component condensation, showing thermal stability and unique chemical properties. Their chemical stability allows for selective transformations, including novel rearrangement reactions, due to the specific properties of the amino group in aminoperoxides.