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The Curtius rearrangement (or Curtius reaction or Curtius degradation), as first defined by Theodor Curtius
Theodor Curtius

Geheimrat Professor Dr. Julius Wilhelm Theodor Curtius was professor of Chemistry at Heidelberg University and elsewhere. He published the Curtius rearrangement in 1890/1894 and also discovered diazoacetic acid, hydrazine and hydrazoic acid....
, is a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 that involves the rearrangement of an acyl azide to an isocyanate
Isocyanate

Isocyanate is the functional group of atoms ?N=C=O , not to be confused with the cyanate functional group which is arranged as ?O?C=N....
. Several reviews have been published.

The isocyanate can be trapped by a variety of nucleophile
Nucleophile

In chemistry, a nucleophile is a reagent that forms a chemical bond to its reaction partner by donating both bonding electrons. Because nucleophiles donate electrons, they are by definition Lewis bases ....
s.






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The Curtius rearrangement (or Curtius reaction or Curtius degradation), as first defined by Theodor Curtius
Theodor Curtius

Geheimrat Professor Dr. Julius Wilhelm Theodor Curtius was professor of Chemistry at Heidelberg University and elsewhere. He published the Curtius rearrangement in 1890/1894 and also discovered diazoacetic acid, hydrazine and hydrazoic acid....
, is a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 that involves the rearrangement of an acyl azide to an isocyanate
Isocyanate

Isocyanate is the functional group of atoms ?N=C=O , not to be confused with the cyanate functional group which is arranged as ?O?C=N....
. Several reviews have been published.

Curtius Rearrangement Scheme
The isocyanate can be trapped by a variety of nucleophile
Nucleophile

In chemistry, a nucleophile is a reagent that forms a chemical bond to its reaction partner by donating both bonding electrons. Because nucleophiles donate electrons, they are by definition Lewis bases ....
s. Often water is added to hydrolyze the isocyanate to an amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
. When done in the presence of tert-butanol
Tert-Butanol

tert-Butanol, or 2-methyl-2-propanol , is the simplest Alcohol#Systematic_names. It is one of the four isomers of butanol. tert-Butanol is a clear liquid with a camphor-like odor....
, the reaction generates Boc-protected
Protecting group

A protecting group or protective group is introduced into a molecule by chemical modification of a functional group in order to obtain chemoselectivity in a subsequent chemical reaction....
 amines, useful intermediates in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
.

Carboxylic acid
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
s 1 can be easily converted to acyl azides 3 using diphenylphosphoryl azide
Diphenylphosphoryl azide

Diphenylphosphoryl azide is an organic compound. It is widely used in synthesis of other organic compounds. Diphenylphosphoryl azide has been obtained by reaction of the phosphorochloridate with sodium azide....
 2.

Dppa Acid To Boc Amine Scheme
Likewise, when the Curtius reaction is performed in the presence of benzyl alcohol
Benzyl alcohol

Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH....
, Cbz-protected amines are formed.

Reaction mechanism

The first step of the Curtius rearrangement is the loss of nitrogen
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
 gas forming an acyl nitrene (2). Once formed, acyl nitrenes very quickly rearrange by migration of R-group forming the desired isocyanate
Isocyanate

Isocyanate is the functional group of atoms ?N=C=O , not to be confused with the cyanate functional group which is arranged as ?O?C=N....
 (3).

Curtius Rearrangement Mechanism

Scope

In one variation called the Darapasky degradation (A. Darapsky, 1936) a Curtius rearrangement takes place as one of the steps from an a-cyanoester to an amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 .

See also

  • Beckmann rearrangement
    Beckmann rearrangement

    The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann , is an acid catalysis rearrangement reaction of an oxime to an amide....
  • Hofmann rearrangement
    Hofmann rearrangement

    The Hofmann rearrangement is the organic chemistry reaction of a primary amide to a primary amine with one fewer carbon atom.The reaction of bromine with sodium hydroxide forms sodium hypobromite in situ, which transforms the primary amide into an intermediate isocyanate....
  • Lossen rearrangement
    Lossen rearrangement

    The Lossen rearrangement is the chemical reaction of a hydroxamic acid 1 with a dehydration agent to form the O-derivative 2, which spontaneously rearranges to form an isocyanate 3....
  • Schmidt reaction
    Schmidt reaction

    The Schmidt reaction is an organic reaction involving alkyl migration over the carbon to nitrogen chemical bond in an azide with expulsion of nitrogen....
  • Tiemann rearrangement
  • Wolff rearrangement
    Wolff rearrangement

    The Wolff rearrangement is a rearrangement reaction converting a a-diazo-ketone into a ketene. This reaction was first reported by Ludwig Wolff in 1912....