Bucherer-Bergs Hydantoin Synthesis. 17 May, / by SK / in Reactions. Overall Score4. Generality. Reagent Availability. Experimental User Friendliness . The Bucherer-Bergs reaction is the chemical reaction of carbonyl compounds (or cyanohydrins) with ammonium carbonate and potassium cyanide to give. The Formation of Hydantoin from Carbonyl Compound with Potassium Cyanide and Ammonium Carbonate is Referred to as the Bucherer-bergs Reaction.

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The Bucherer—Bergs reaction is the chemical reaction of carbonyl compounds aldehydes or ketones or cyanohydrins with ammonium carbonate and potassium cyanide to give hydantoins. The addition of KCN to the carbonyl compound gives rise to the cyanohydrin.

This is followed by an S N 2 reaction with NH 3 to form aminonitrile. Nucleophilic addition of aminonitrile to CO 2 leads to cyano-carbamic acid, which undergoes an intramolecular ring closing to 5-imino-oxazolidinone. The 5-imino-oxazolidinone rearranges to form the hydantoin reacttion via an isocyanate intermediate. Reactions similar to the Bucherer—Bergs reaction were first bhcherer in and by Ciamician and Silber, who obtained 5,5-dimethylhydantoin from a mixture of acetone and hydrocyanic acid after it had been exposed to sunlight for five to seven months.

InBergs issued a patent that described his own synthesis of a number of 5-substituted hydantoins. Bucherer and Steiner also found that cyanohydrins would react just as well as carbonyl compounds to produce hydantoins. With this solvent, aldehydes reacted well, and ketones gave buchreer yields. In Bucherer and Steiner proposed a mechanism for the reaction. While there were some issues with the mechanism, it was mostly accurate.


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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 reactipn 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 one-pot synthesis see Figure 1.

First, the reaction of 2-Methyleneaziridine 1 with Grignard reagentcatalytic Cu Iand R 2 -X causes the 2-Methyleneaziridine to ring open and form 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.

One improvement on the Bucherer—Bergs reaction has been the use of ultrasonication.

Bucherer-Bergs reaction

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. 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.

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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 see Figure 2. In some cases, the carbonyl starting material can be sufficiently sterically biased so a single stereoisomer is observed.

However, in other cases, there is no selectivity at all, resulting in a 1: An example taken from “Name Reactions: While the end product of the Bucherer—Bergs reaction is a hydantointhe hydantoin can undergo reactiob to form an aminio acid.

This is what is assumed in the example below. For comparison, bbucherer amino acid product for the Strecker synthesis has also been included. The hydantoins formed by the Bucherer—Bergs reaction have many useful applications.

Bucherer—Bergs reaction The Bucherer—Bergs reaction is the chemical reaction of carbonyl compounds aldehydes or ketones or cyanohydrins with ammonium carbonate and potassium cyanide to give hydantoins. Tetrahedron Letters47 Ultrasonics Sonochemistry3SS Heterocyclic ChemistryHoboken, New Jersey: