Acyl cyanide explained

In organic chemistry, an acyl cyanide is a functional group with the formula and structure . It consists of an acyl group attached to cyanide . Examples include acetyl cyanide, formyl cyanide, and oxalyl dicyanide. Acyl cyanides are reagents in organic synthesis.^{[1] [2]}

Synthesis

Classically acyl cyanides are produced by the salt metathesis reaction of acyl chlorides with sodium cyanide:

$\backslash ce\; +\; \backslash ce\; \backslash longrightarrow\; +\; \backslash ce$Alternatively, they can be produced by dehydration of acyl aldoximes:

$\backslash ce\backslash ce\; \backslash longrightarrow\; +\; \backslash ce$Acetyl cyanide is also prepared by hydrocyanation of ketene:

$\backslash ce\; +\; \backslash ce\; \backslash longrightarrow\; \backslash ce$

Reactions

They are mild acylating agents.^[2] With aqueous base, acyl cyanides break down to cyanide and the carboxylate:^[3]

$+\; \backslash ce\; \backslash longrightarrow\; \backslash ce\; +\; \backslash ce\; +\; \backslash ce$

With azides, acyl cyanides undergo the click reaction to give acyl tetrazoles.^[4]

References

1. 10.1021/acs.orglett.8b01180. Stereoselective Synthesis of Fully-Substituted Acrylonitriles via Formal Acylcyanation of Electron-Rich Alkynes. 2018. Liu. Bing. Wang. Yong. Chen. Ying. Wu. Qian. Zhao. Jing. Sun. Jianwei. Organic Letters. 20. 12. 3465–3468. 29873500. 46942109.
2. Book: 10.1002/047084289X.ra026. Acetyl Cyanide. Encyclopedia of Reagents for Organic Synthesis. 2001. Morris. Joel. 0471936235.
3. 10.1002/anie.198200361. The Chemistry of Acyl Cyanides. 1982. Hünig. Siegfried. Schaller. Rainer. Angewandte Chemie International Edition in English. 21. 36–49.
4. 10.1002/1521-3773(20020617)41:12<2113::AID-ANIE2113>3.0.CO;2-Q. A Click Chemistry Approach to Tetrazoles by Huisgen 1,3-Dipolar Cycloaddition: Synthesis of 5-Acyltetrazoles from Azides and Acyl Cyanides. 2002. Demko. Zachary P.. Sharpless. K. Barry. Angewandte Chemie International Edition. 41. 12. 2113–2116. 19746613.