Synthesis 2009(2): 332-334  
DOI: 10.1055/s-0028-1083274
PSP
© Georg Thieme Verlag Stuttgart ˙ New York

A Convenient Preparation of Di-p-chlorobenzyl Azodicarboxylate (DCAD) for Mitsunobu Couplings

Benjamin R. Taft, Elizabeth C. Swift, Bruce H. Lipshutz*
Department of Chemistry & Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
Fax: +1(805)8938265; e-Mail: [email protected];
Further Information

Publication History

Received 27 August 2008
Publication Date:
12 December 2008 (online)

Abstract

Gram-scale synthesis of pure, bench-stable solid di-p-chlorobenzyl azodicarboxylate (DCAD) is performed in two steps without resorting to chromatography. This novel reagent effects Mitsunobu couplings with yields comparable to DEAD or DIAD, while addressing several of the drawbacks frequently associated with these common reagents.

    References

  • 1 Toy PH. But TYS. Chem. Asian J.  2007,  2:  1340 
  • 2 Dembinski R. Eur. J. Org. Chem.  2004,  2763 
  • 3a Lipshutz BH. Chung DW. Rich B. Corral R. Org. Lett.  2006,  8:  5069 
  • 3b

    Our originally reported R f for the hydrazine dicarboxylate 4 is misleading, as the material was impure due to the presence of residual imidazole.

4

Optimum results were achieved using CDI and CBA obtained from Alfa Aesar.

5

Imidazole is water soluble while 4 is not. Use of 1:1 hexanes-Et2O leads to substantial loss of product 4. Exposure time of the product to solvent can be minimized by using vacuum filtration.