[764-05-6] · CN4 · Cyanogen Azide · (MW 68.04)
(1,3-dipolar reagent that undergoes cycloaddition and insertion reactions with alkenes2)
Preparative Methods: by the addition of cyanogen chloride or Cyanogen Bromide to an acetonitrile solution of Sodium Azide in the temperature range of 10-25 °C. The reagent is used in solution after filtration or decantation of the inorganic salts.1,3
Handling, Storage, and Precautions: should be used in solution. In acetonitrile a 27% by weight solution of cyanogen azide has a half-life of 15 days at 25 °C. The pure material is highly explosive and detonates violently when exposed to mild thermal, mechanical, or electrical shock.1,3 This reagent should be handled in a fume hood.
Cycloaddition of cyanogen azide to alkenes affords both aziridines and alkylidenecyanamides. The ratio of the two products depends on the structure of the starting alkene. Isobutene, for example, yields a 1.4:1 mixture of 2-butylidenecyanamide and N-cyano-2,2-dimethylaziridine (eq 1).3,4 The alkylidenecyanamide is formed by a Demjanoff-like rearrangement of a dipolar intermediate resulting from cleavage of the initially formed triazoline.
In contrast to the acyclic case, with cyclopentene the only product is the cyanamide, hydrolysis of which affords cyclopentanone in high yield (eq 2). Strained bicyclic alkenes, however, lead to the opposite result. Norbornene upon treatment with cyanogen azide affords a mixture of aziridine and cyanamide in a ratio of 4:1 (eq 3).4
Ring contraction is also observed for cycloalkenes with trisubstituted double bonds (eq 4).4
In the presence of Lithium Perchlorate, methylenecyclohexanes and -cyclohexenes undergo ring enlargement to yield cyclic ketones when treated first with cyanogen azide and then with methanolic HCl (eqs 5 and 6).5,6
Ring enlargement is also observed in the absence of the perchlorate salt (eq 7).7
Dihydro-8-10 and tetrahydropyridines11,12 afford cyanoaziridines when treated with cyanogen azide (eqs 8 and 9).
Thermal decomposition of cyanogen azide leads to a nitrene intermediate which may insert into C-H bonds (eq 10); a nitrene is also proposed for the reaction of cyanogen azide with benzene to give cyanoazepine (eq 11).
Emory University, Atlanta, GA, USA