Diphenyl Phosphonate1

[4712-55-4]  · C12H11O3P  · Diphenyl Phosphonate  · (MW 234.20)

(mild coupling agent for synthesis of esters and amides)

Alternate Name: diphenyl phosphite.

Physical Data: mp 12 °C (25 °C);1a bp 100 °C/0.008 mmHg, 218-219 °C/26 mmHg; n25D 1.5564-1.5570; d 31P 1.9 (1JPH 756 Hz).

Solubility: misc most organic solvents; hydrolyzes readily to the monoester, d 31P 4.0 (1JPH 719).

Form Supplied in: colorless liquid, widely available, containing up to 15% of phenol.

Purification: distillation.2 Best done in small batches since decomposition frequently occurs. Phenol can be substantially removed by heating at 150 °C at water pump vacuum.

Handling, Storage, and Precautions: no toxicity data have been reported but the invariable presence of phenol and its ready hydrolysis by atmospheric moisture makes the commerical material corrosive.

In the presence of tertiary amines, preferably Pyridine or Imidazole, the ester acts as an efficient coupling agent in the formation of peptides (eq 1).1,3 Ureas and thioureas may be similarly prepared from Carbon Dioxide or Carbon Disulfide (eq 2).4

The diester undergoes easy transesterification in two distinct stages, allowing the preparation of unsymmetrical diesters (eq 3).5

The use of stronger bases than pyridine, e.g. Triethylamine, causes rapid disproportionation to (PhO)3P and PhOPHO2-.2c,5

1. Stelzel, P. MOC 1974, 15/2, 246.
2. (a) Houalla, D.; Wolf, R. CR 1958, 247, 482; (b) Walsh, E. N. JACS 1959, 81, 3023; (c) Yamazaki, N.; Iguchi, T.; Higashi, F. CL 1977, 185.
3. (a) Yamazaki, N.; Higushi, F. TL 1972, 5047; (b) Yamazaki, N.; Higashi, F. TL 1974, 1323.
4. Yamazaki, N.; Higashi, F.; Iguchi, T. TL 1974, 1191.
5. Gallagher, M. J.; Garbutt, R.; Liu Yuan Hua; Gum Hee Lee. PS 1993, 201.

Michael J. Gallagher

University of New South Wales, Kensington, NSW, Australia

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.