Acyl azide explained

Acyl azides are carboxylic acid derivatives with the general formula RCON₃. These compounds, which are a subclass of organic azides, are generally colorless.^[1]

Preparation

Typically acyl azides are generated under conditions where they rearrange to the isocyanate.^[1]

Alkyl or aryl acyl chlorides react with sodium azide to give acyl azides.

The second major route to azides is from the acyl hydrazides with nitrous acid.^[1]

Acyl azides have also been synthesized from various carboxylic acids and sodium azide in presence of triphenylphosphine and trichloroacetonitrile catalysts in excellent yields at mild conditions.^[2] Another route starts with aliphatic and aromatic aldehydes reacting with iodine azide which is formed from sodium azide and iodine monochloride in acetonitrile.^[3]

Uses

On Curtius rearrangement, acyl azides yield isocyanates.^{[4] [5]}

Acyl azides are also formed in Darapsky degradation,^{[6] [7] [8]}

Historical references

• Ueber Stickstoffwasserstoffsäure (Azoimid) N₃H . Curtius . Th. . Theodor Curtius . . 1890 . 23 . 2 . 3023–3033 . German . 10.1002/cber.189002302232.
• 10.1002/prac.18940500125 . 20. Hydrazide und Azide organischer Säuren I. Abhandlung . 1894 . Curtius . Th. . Theodor Curtius . . 50 . 1 . 275–294 . German.
• August . Darapsky . . 146 . 250–267 . 1936 . 10.1002/prac.19361460806 . Darstellung von α-Aminosäuren aus Alkyl-cyanessigsäuren . German . 8–12.
• August . Darapsky . Dietrich . Hillers . . 92 . 1 . 297–341 . 1915 . 10.1002/prac.19150920117 . Über das Hydrazid der Cyanessigsäure, Isonitrosocyanessigsäure und Nitrocyanessigsäure . German.

Notes and References

1. Book: Saul Patai. 10.1002/9780470771266.ch9. Acyl azides. The Azido Group. 1971. Lwowski. Walter . 849–907. 9780470771679. PATAI'S Chemistry of Functional Groups.
2. 10.1055/s-2008-1077979 . Direct Synthesis of Acyl Azides from Carboxylic Acids by the Combination of Trichloroacetonitrile, Triphenylphosphine and Sodium Azide . 2008 . Jang . Doo . Kim . Joong-Gon . . 2008 . 13 . 2072–2074.
3. 10.1021/jo035163v . Radical Azidonation of Aldehydes . 2003 . Marinescu . Lavinia . Thinggaard . Jacob . Thomsen . Ib B. . Bols . Mikael . . 68 . 24 . 9453–9455 . 14629171 .
4. The Curtius reaction . Smith . Peter A. S. . . 1946 . 3 . 337–449 . 10.1002/0471264180.or003.09. 0471264180 .
5. 10.1021/cr00084a001 . Azides: Their preparation and synthetic uses . 1988 . Scriven . Eric F. V. . Turnbull . Kenneth . . 88 . 2 . 297–368.
6. Paul E. . Gagnon . Paul A. . Boivin . Hugh M. . Craig . . 29 . 1 . 70–75 . 1951 . 10.1139/v51-009 . Synthesis of Amino Acids from Substituted Cyanoacetic Esters. free .
7. Book: E. H. Rodd . Chemistry of Carbon Compounds . 2nd . 1157 . New York . 1965.
8. . 30 . 592–597 . 1952 . 10.1139/v52-071 . Synthesis of α-Amino Acids from Ethyl Cyanoacetate . Gagnon . Paul E. . Nadeau . Guy . Côté . Raymond . 8. free .