Diethyl azodicarboxylate
Diethyl azodicarboxylate, often abbreviated DEAD, is the organic compound CH3CH2O2CN=NCO2CH2CH3. As indicated with this formula, the molecule consists of a central azo functional group, RN=NR, flanked by two ethyl ester groups. This red orange liquid is a valuable reagent but also quite dangerous.
Preparation
Although widely available, diethyl azodicarboxylate can be prepared in the laboratory. A two-step synthesis starts from hydrazine, first by alkylation with ethyl chloroformate. followed by treating the resulting ethyl hydrazodicarboxylate with chlorine.[1]
- 2 CH3CH2O2CCl + N2H4 → CH3CH2O2CN(H)N(H)CO2CH2CH3 + 2 HCl
- CH3CH2O2CN(H)N(H)CO2CH2CH3 + Cl2 → CH3CH2O2CN=NCO2CH2CH3 + 2 HCl
Red fuming nitric acid can also be used in the second step.[2]
Applications
DEAD is an efficient component in Diels-Alder reactions and in click chemistry, for example the synthesis of Bicyclo[2.1.0]pentane, which originates from Otto Diels.[3]
DEAD is an important reagent in the Mitsunobu reaction where it forms an adduct with phosphines. In one study [4] the compound together with triphenylphosphine and a chalcone formed a pyrazoline:
Safety
DEAD is toxic, shock sensitive, and thermally unstable. It is handled as a solution, rarely as the pure compound.
References
- ↑ Rabjohn, N. “Diethyl azodicarboxylate” Organic Syntheses 28:58; Coll. Vol. 3:375.
- ↑ “Diethyl azodicarboxylate]” Kauer, J. C. Organic Syntheses, Collective Volume 4, page 411.
- ↑ Gassman, P. G.;Mansfield, K. T. “Bicyclo(2.1.0)pentane“. Org. Synth. 49:1; Coll. Vol. 5:96
- ↑ A Novel Reaction of the “Huisgen Zwitterion” with Chalcones and Dienones: An Efficient Strategy for the Synthesis of Pyrazoline and Pyrazolopyridazine Derivatives Vijay Nair, Smitha C. Mathew, Akkattu T. Biju, and Eringathodi Suresh Angew. Chem. Int. Ed. 2007, 46, 2070 –2073 doi:10.1002/anie.200604025
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