Surf Wiki
Save to docs
general/halogenation-reactions

From Surf Wiki (app.surf) — the open knowledge base

Balz–Schiemann reaction

Chemical reaction

Chemical reaction

Günther Schiemann The Balz–Schiemann reaction (also called the Schiemann reaction) is a chemical reaction in which a primary aromatic amine is transformed to an aryl fluoride via a diazonium tetrafluoroborate intermediate. This reaction is a traditional route to fluorobenzene and some related derivatives, including 4-fluorobenzoic acid.

:[[File:Balz-Schiemann Reaction.png|500px|Balz–Schiemann reaction]]

The reaction is conceptually similar to the Sandmeyer reaction, which converts diazonium salts to other aryl halides (ArCl, ArBr). However, while the Sandmeyer reaction involves a copper reagent/catalyst and radical intermediates, the thermal decomposition of the diazonium tetrafluoroborate proceeds without a promoter and is believed to generate highly unstable aryl cations (Ar+), which abstract F− from BF4− to give the fluoroarene (ArF), along with boron trifluoride and nitrogen as the byproducts.

Innovations

The traditional Balz–Schiemann reaction employs HBF4 and involves isolation of the diazonium salt. Both aspects can be profitably modified. Other counterions have been used in place of tetrafluoroborates, such as hexafluorophosphates (PF6−) and hexafluoroantimonates (SbF6−) with improved yields for some substrates. The diazotization reaction can be effected with nitrosonium salts such as [NO]SbF6 without isolation of the diazonium intermediate.

As a practical matter, the traditional Balz–Schiemann reaction consumes relatively expensive BF4− as a source of fluoride. An alternative methodology produces the fluoride salt of the diazonium compound. In this implementation, the diazotization is conducted with a solution of sodium nitrite in liquid hydrogen fluoride: : :

History

The reaction is named after the German chemists and Günther Balz.

Examples

4-Fluorotoluene is made in ~89% yield by Balz–Schiemann reaction on p-toluidine. This is then used as a precursor for 4-fluorobenzaldehyde,

Balz–Schiemann reaction is used in the synthesis of DOF & 2C-F. The starting material for the first step in the synthesis is called 2,5-dimethoxyaniline [102-56-7].

The Balz–Schiemann reaction is used in the synthesis of Fipamezole from Atipamezole.

Additional literature

References

References

  1. (1927). "Über aromatische Fluorverbindungen, I.: Ein neues Verfahren zu ihrer Darstellung". [[Chemische Berichte]].
  2. (2007). "Advanced Organic Chemistry: Part B: Reactions and Synthesis". Springer.
  3. Flood, D. T.. (1943). "Fluorobenzene".
  4. (1943). "''p''-Fluorobenzoic Acid".
  5. (1975). "Mechanism of formation of aryl fluorides from arenediazonium fluoborates". [[J. Am. Chem. Soc.]].
  6. (2007). "Advanced Organic Chemistry: Part B: Reactions and Synthesis". Springer.
  7. (1961). "The Use of Hexafluorophosphoric Acid in the Schiemann Reaction". [[The Journal of Organic Chemistry]].
  8. (1968). "The use of arenediazonium hexafluoro-antimonates and -arsenates in the preparation of aryl fluorides". Journal of the Chemical Society C: Organic.
  9. (2010). "C–F Bond Formation for the Synthesis of Aryl Fluorides". Synthesis.
  10. (2000). "Ullmann's Encyclopedia of Industrial Chemistry".
  11. (March 2013). "Continuous flow reactor for Balz–Schiemann reaction: a new procedure for the preparation of aromatic fluorides". Tetrahedron Letters.
  12. (2001). "Benzylic oxidation of aromatics with cerium(IV) triflate; synthetic scope and mechanistic insight". Journal of the Chemical Society, Perkin Transactions 1.
  13. Arto Johannes Karjalainen, et al. WO1993013074 (to Orion Oyj).
Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

halogenation-reactions substitution-reactions name-reactions
Want to explore this topic further?

Ask Mako anything about Balz–Schiemann reaction — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report