Diphenylphosphoryl azide
Encyclopedia
Diphenylphosphoryl azide (DPPA; IUPAC name: Diphenyl phosphorazidate) is an organic compound. It is widely used in synthesis of other organic compounds.
. The stability of the azide towards heating was shown by its distillation at 157 °C and by the fact that vigorous evolution of nitrogen was not observed until a temperature of 175 °C had been reached.
replacement of the azido group by treatment with nucleophilic reagents, such as water, butanol, ammonia, and various amines.
This compound is used as a reagent for the synthesis of peptides by virtue of its reactions with carboxylic acids leading to either the urethane or the amide. The formation of the urethane is particularly valuable since it works with carboxylic acids which fail to undergo the Schmidt reaction
, and is believed to involve transfer of the azido group to the carboxylic acid.
It is now suggested that this reaction proceeds through the intermediate mixed anhydride, resulting from attack by the nucleophilic carboxylate anion on the phosphorus atom, with expulsion of the azide ion. The latter then attacks the carbonyl carbon atom, to give the acyl azide and loss of the diphenyl phosphate anion, known to be a good leaving group. Finally, the acyl azide reacts in the normal manner to give the urethane.
The present studies show that diphenylphosphoryl azide reacts with amines giving the corresponding phosphoramidates; it therefore appears that formation of the amide similarly involves the intermediate anhydride, followed by nucleophilic substitution by the amine.
Synthesis
Diphenylphosphoryl azide has been obtained by reaction of the phosphorochloridate with sodium azideSodium azide
Sodium azide is the inorganic compound with the formula NaN3. This colourless azide salt is the gas-forming component in many car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance and is highly soluble in water. It is extremely...
. The stability of the azide towards heating was shown by its distillation at 157 °C and by the fact that vigorous evolution of nitrogen was not observed until a temperature of 175 °C had been reached.
Uses
This compound undergoes pseudohalogenPseudohalogen
Pseudo'halogen molecules are inorganic molecules of the general formsPs–Ps or Ps–X, where Ps is a pseudohalogen group such as cyanide, cyanate, thiocyanate and others, and X is a "true" halogen...
replacement of the azido group by treatment with nucleophilic reagents, such as water, butanol, ammonia, and various amines.
This compound is used as a reagent for the synthesis of peptides by virtue of its reactions with carboxylic acids leading to either the urethane or the amide. The formation of the urethane is particularly valuable since it works with carboxylic acids which fail to undergo the Schmidt reaction
Schmidt reaction
The Schmidt reaction is an organic reaction involving alkyl migration over the carbon-nitrogen chemical bond in an azide with expulsion of nitrogen...
, and is believed to involve transfer of the azido group to the carboxylic acid.
It is now suggested that this reaction proceeds through the intermediate mixed anhydride, resulting from attack by the nucleophilic carboxylate anion on the phosphorus atom, with expulsion of the azide ion. The latter then attacks the carbonyl carbon atom, to give the acyl azide and loss of the diphenyl phosphate anion, known to be a good leaving group. Finally, the acyl azide reacts in the normal manner to give the urethane.
The present studies show that diphenylphosphoryl azide reacts with amines giving the corresponding phosphoramidates; it therefore appears that formation of the amide similarly involves the intermediate anhydride, followed by nucleophilic substitution by the amine.