Diphenylphosphoryl azide
[CAS 26386-88-9]

Identification

• Classification: Chemical reagent >> Organic reagent >> Phosphine ligand
• Name: Diphenylphosphoryl azide
• Synonyms: Phosphoric acid diphenyl ester azide; DPPA
• Molecular Formula: C₁₂H₁₀N₃O₃P
• Molecular Weight: 275.20
• CAS Registry Number: 26386-88-9
• EC Number: 247-644-0
• SMILES: C1=CC=C(C=C1)OP(=O)(N=[N+]=[N-])OC2=CC=CC=C2

Properties

• Density: 1.277 g/mL (Expl.)
• Boiling point: 157 °C (0.2 mmHg) (Expl.)
• Flash point: 112 °C (Expl.)
• Solubility: water: insoluble (Expl.)
• Refraction index: 1.552 (Expl.)

Safety Data

• Hazard Symbols: GHS06;GHS07 Danger
• Risk Statements: H301-H310-H311-H315-H319-H330-H331-H335
• Safety Statements: P260-P261-P262-P264-P264+P265-P270-P271-P280-P284-P301+P316-P302+P352-P304+P340-P305+P351+P338-P316-P319-P320-P321-P330-P332+P317-P337+P317-P361+P364-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	3	H301
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	3	H331
Acute toxicity	Acute Tox.	2	H330
Acute toxicity	Acute Tox.	2	H310
Eye irritation	Eye Irrit.	2A	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute toxicity	Acute Tox.	2	H300
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400

• Transport Information: UN 3278

chemBlink Chemical Story

Diphenylphosphoryl azide, CAS 26386-88-9, universally abbreviated DPPA, is one of the best-known multifunctional reagents in modern organic synthesis. It was introduced by Takayuki Shioiri, Koichi Ninomiya and Shun-ichi Yamada in 1972 as a convenient reagent for a modified Curtius reaction and for peptide synthesis. The molecule combines a diphenyl phosphate framework with an azide group attached to phosphorus.

Its classic role is the Curtius rearrangement. A carboxylic acid can be activated by DPPA to generate an acyl azide, which on heating rearranges to an isocyanate with loss of nitrogen. The isocyanate can then react with water, alcohols or amines to furnish amines, carbamates or ureas. This sequence effectively converts the carbonyl carbon of a carboxylic acid into a nitrogen-containing product and is widely used because the reaction can often be carried out under relatively mild conditions.

DPPA also functions as a peptide-coupling or condensing reagent. In peptide synthesis, activation of a carboxyl group allows an amine to form the new amide bond. The original 1972 report specifically emphasized both modified Curtius chemistry and peptide synthesis, and later literature expanded DPPA use into azidation and many complex natural-product syntheses.

The reagent's versatility comes from controlled transfer of azide and activation at phosphorus, but azide chemistry requires respect. Organic azides can be energetic, and DPPA is toxic and reactive. Its reputation as a convenient liquid reagent does not remove the need for appropriate scale, temperature control and safety procedures.

DPPA is a particularly good example of a reagent becoming more important than the single reaction for which it was first introduced. Its name is now encountered in rearrangement, amide formation, azidation and complex synthesis. A phosphorus reagent carrying an azide group became a bridge between carboxylic-acid chemistry and nitrogen chemistry.

References:
1. Shioiri T, Ninomiya K, Yamada S. Diphenylphosphoryl azide. New convenient reagent for a modified Curtius reaction and for peptide synthesis. J Am Chem Soc. 1972;94:6203-6205.
2. TCI America, Diphenylphosphoryl Azide, CAS 26386-88-9.
3. Scriven EFV, Turnbull K. Azides: their preparation and synthetic uses. Chem Rev. 1988;88:297-368.

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