Bucherer–Bergs reaction

Source: Wikipedia, the free encyclopedia.
Bucherer–Bergs reaction
Named after Hans Theodor Bucherer
Hermann Bergs
Reaction type Ring forming reaction
Identifiers
Organic Chemistry Portal bucherer-bergs-reaction

The Bucherer–Bergs reaction is the

ketones) or cyanohydrins with ammonium carbonate and potassium cyanide to give hydantoins.[1][2][3][4] The reaction is named after Hans Theodor Bucherer
.

The Bucherer-Bergs reaction
The Bucherer-Bergs reaction

Reaction mechanism

Reaction mechanism for the Bucherer–Bergs reaction

Following condensation of the carbonyl with the ammonium, the formed imine is attacked by the isocyanide to form the aminonitrile. Nucleophilic addition of aminonitrile to CO2 leads to cyano-carbamic acid, which undergoes an intramolecular ring closing to 5-imino-oxazolidin-2-one. The 5-imino-oxazolidin-2-one rearranges to form the hydantoin product via an isocyanate intermediate. [citation needed]

History

Reactions similar to the Bucherer–Bergs reaction were first seen in 1905 and 1914 by Ciamician and Silber, who obtained 5,5-dimethylhydantoin from a mixture of

ketones gave excellent yields. In 1934 Bucherer and Steiner proposed a mechanism for the reaction. While there were some issues with the mechanism, it was mostly accurate.[5]

Limitations

One limitation of the Bucherer–Bergs reactions is that it only has one point of diversity. Only changes in the structure of the starting ketone or aldehyde will lead to variations in the final hydantoin.

One way to increase the number of points of diversity is by combining a reaction with 2-Methyleneaziridine with the Bucherer–Bergs reaction in a

ketimine 2. The ketimine is then subjected to the Bucherer-Bergs reagents, resulting in a 5,5'- disubstituted hydantoin 3. This reaction has three points of chemical diversity as the structure of the aziridine starting compound, the organometallic reagent, and the electrophile can all be varied to synthesize a different hydantoin.[6]

Improvements

One improvement on the Bucherer–Bergs reaction has been the use of ultrasonication. More recently, many organic reactions have been accelerated by ultrasonic irradiation. In the past, the Bucherer–Bergs reaction has had problems with polymerization, long reaction time, and difficult work-up. 5,5-disubstituted hydantoins can be prepared using the Bucherer–Bergs reaction under ultrasonication. Compared with reports in the literature, this makes so the reaction can be carried out at a lower temperature, have a shorter reaction time, a higher yield, and a more simple work-up.[7]

Variations

One variation of the Bucherer–Bergs reaction is the treatment of carbonyl compound with carbon disulfide and ammonium cyanide in methanol solution to form 2,4-dithiohydantoins.[8] In addition, the reaction of ketones with ammonium monothiocarbamate and sodium cyanide will yield 5,5-disubstituted 4-thiohydantoins.[9]

Stereospecificity

In some cases, the carbonyl starting material can be sufficiently sterically biased so a single

Strecker synthesis has also been included.[10]

Applications

The hydantoins formed by the Bucherer–Bergs reaction have many useful applications. They:

See also

References

  1. J. Prakt. Chem.
    1934, 140, 69.
  2. J. Prakt. Chem.
    1934, 140, 291.
  3. ^ Bergs, H. Ger. pat. 566,094 (1929).
  4. doi:10.1021/cr60145a001
  5. doi:10.1021/cr60145a001
  6. Tetrahedron Lett.
    2006, 47, 9207-9209.
  7. ^ Li, J.; Li, L.; Li, T.; Li, H.; Liu, J. Ultrasonics Sonochemistry 1996, 3, S141-S143.
  8. J. Chem. Soc.
    1947, 681.
  9. J. Chem. Soc.
    1959, 396.
  10. ^ Li, J.J. Name Reactions: Heterocyclic Chemistry, Hoboken, New Jersey: John Wiley & Sons, Inc., 2005.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Bucherer–Bergs_reaction&oldid=1213819827"