Bucherer–Bergs reaction

The Bucherer -Bergs synthesis or Bucherer -Bergs reaction is a reaction in organic chemistry. With the help of this reaction carbonyl groups in hydantoins are converted. Act as solvents ethanol and water. It is named after the German chemist Hans Theodor Bucherer (1869-1949) and Hermann Berg named.

Mechanism

In this reaction, an aldehyde or ketone to react with ammonium carbonate and a cyanide hydantoin.

Initially it is the carbonyl compound (1 ) was reacted with ammonium carbonate. It forms an ammonium ion ( 2). This is mixed with cyanide from cyanide or potassium cyanide. The reaction product (3) contains both an amino group and a nitrile group. The amino group is now attacks the carbon dioxide which was released by the reaction of the carbonyl compound (1) with ammonium carbonate. It forms a carbamate ion ( 4 ), which is a proton transfer to carbamate (5). Then an intramolecular attack of an Sauerstoffteilchens on the carbon atom of the nitrile group takes place. This is a heterocyclic Fünfringing (6) is formed, which again undergoes a proton transfer. The result (7). Thereafter, the five-membered ring breaks down again, there is formed ( 8). There is a change in position between the amino group and the carbonyl group instead of (9). This allows the amino group of an intramolecular attack on a carbon atom, which again forms a five-membered ring (10). Through a last proton transfer leads to the hydantoin 11

Applications

For the substances resulting from the Bucherer -Bergs synthesis hydantoins in the laboratory and in industry are numerous practical applications:

• Synthesis of heterocyclic agents, such as the drug 5,5- diphenylhydantoin ( phenytoin)
• Starting materials are prepared for industrial production of amino acids such as methionine which several 100,000 tons per year; World market leader for this is Evonik Industries
• Production of sugar derivatives