Iron(III) Azide1

Fe(N3)3

[14215-32-8]  · FeN9  · Iron(III) Azide  · (MW 181.94)

(preparation of azidoalkanes1)

Alternate Name: ferric azide.

Form Supplied in: made in situ.

Preparative Methods: the reagent is prepared and used in situ1 by addition of Sodium Azide (15 mmol) and Iron(III) Sulfate (7.5 mmol) in methanol (20 mL) to the organoborane (5 mmol) stirred at rt for 30 min under nitrogen. The mixture is then cooled to 0 °C and 30% Hydrogen Peroxide added via a syringe pump (0.1 mL min-1). Slow addition of hydrogen peroxide increases yields.

Handling, Storage, and Precautions: is poisonous by ingestion or skin contact. It is an unstable explosive, sensitive to impact. Decomposition yields toxic fumes of NOx and Na2O. Organic azides are sensitized by metal salts or traces of strong acid.8 Fe2(SO4)3 is harmful if swallowed or inhaled. It causes eye and skin irritation. Use in a fume hood.

Azidoalkanes.1

Azidoalkanes are useful intermediates in the synthesis of a variety of nitrogen derivatives, especially amines via reduction with Lithium Aluminum Hydride. Trialkylboranes react with iron azide in the presence of hydrogen peroxide to generate alkyl azides (eq 1) at rt.1 This procedure provides a good overall transformation of alkenes to azides in an anti-Markovnikov fashion, via conversion to the organoborane followed by the one-pot azidation with Fe(N3)3 (eqs 2-4). Secondary amines can be made stereospecifically via thermal conversion of an alkyl azide to a nitrene and reaction with an alkyl dichloroborane.2

Reaction mixtures (5 mmol scale) are worked up with 3 N NaOH (20 mL) and 30% H2O2 to decompose residual organoborane. The products are extracted into ether.1 Alternate procedures for generation of alkyl azides are available: nucleophilic displacement with azide ion3 (high temperatures) and use of lead azide generated in situ from lead(IV) acetate azide4 (toxicity and formation of regioisomers) offer no advantages over the iron azide method. The azidation reaction is related to the use of Iron(III) Chloride, Iron(III) Thiocyanate, and Fe(SeCN)3 to generate alkyl halides,5 thiocyanates,5 and selenocyanates,6 respectively. The Fe(N3)3 reaction mechanism is postulated to be different from the latter salts, being a radical process1 thought to be initiated by H2O2 and trace FeII always present in Fe2(SO4)3.7


1. Suzuki, A.; Ishidoya, M.; Tabata, M. S 1976, 687.
2. Brown, H. C.; Midland, M. M.; Levy, A. B. T 1987, 43, 4079.
3. Biffin, M. E. C.; Miller, J.; Paul, D. B. The Chemistry of the Azido group; Interscience: London, 1971; p. 57.
4. Masuda, Y.; Hoshi, M.; Arase, A. BCJ 1984, 57, 1026.
5. Arase, A.; Masuda, Y.; Suzuki, A. BCJ 1974, 47, 2511.
6. Arase, A.; Masuda, Y. CL 1976, 785.
7. (a) Lieser, K. H. Z. Elektrochem. 1960, 64, 252; 1962, 66, 19; 23. (b) Tamura, H.; Goto, K.; Yotsuyanagi, T.; Nagayama, M. Talanta 1974, 21, 314.
8. Lewis, R. J., Sr Hazardous Chemicals Desk Reference; Van Nostrand Reinhold: New York, 1991; pp 100, 1045.

Andrew D. White

Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA



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