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

Benjamin R. Taft; Elizabeth C. Swift; Bruce H. Lipshutz

doi:10.1055/s-0028-1083274

PSP

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: Lipshutz@chem.ucsb.edu;

Abstract

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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.

Keywords

Mitsunobu reaction - azo compounds - alcohols - esters - DCAD

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Referenzen

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.