2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

Preparation

Synthesis of DDQ involves cyanation of chloranil. J. Thiele and F. Günther first reported a 6-step preparation in 1906. The substance did not receive interest until its potential as a dehydrogenation agent was discovered. A single-step chlorination from 2,3-dicyanohydroquinone was reported in 1965.

Reactions

The reagent removes pairs of H atoms from organic molecules. The stoichiometry of its action is illustrated by the conversion of tetralin to naphthalene: :2 C6Cl2(CN)2O2 + C10H12 → 2 C6Cl2(CN)2(OH)2 + C10H8

The resulting hydroquinone is poorly soluble in typical reaction solvents (dioxane, benzene, alkanes), which facilitates workup.

Solutions of DDQ in benzene are red, due to the formation of a charge-transfer complex.

Dehydrogenation

:[[File:DDQ dehydrogenation.svg|400px]]

Aromatization

:[[File:DDQ aromatization rearrangement.png|400px]]

Cross-Dehydrogenative Coupling

:[[File:DDQ-oxi-coupling1.png|400px]] :

Safety

DDQ reacts with water to release highly toxic hydrogen cyanide (HCN).

References

References

1. [https://www.sigmaaldrich.com/US/en/product/aldrich/d60400 2,3-Dichloro-5,6-dicyano-''p''-benzoquinone] at [[Sigma-Aldrich]]
2. (2014). "Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book)". [[Royal Society of Chemistry.
3. (1956). "593. Hydrogen Transfer. Part IX The Selective Dehydrogenation of Unsaturated Alcohols by High-potential Quinones". [[Journal of the Chemical Society (Resumed)]].
4. Becker, H. D.. (1965). "Quinone Dehydrogenation. I. Oxidation of Monohydric Phenols". [[Journal of Organic Chemistry]].
5. (1967). "Applications of High-potential Quinones. Part I. The Mechanism of Dehydrogenation of Steroidal Ketones by 2,3-Dichloro-5,6-Dicyanobenzoquinone". [[Journal of the Chemical Society C: Organic]].
6. (2005). "2,3-Dichloro-5,6-dicyano-1,4-benzoquinone".
7. (1906). "Ueber Abkömmlinge des Dicyanhydrochinons". [[Justus Liebig's Annalen der Chemie]].
8. (1965). "2,3-Dichloro-5,6-Dicyanobenzoquinone (DDQ). A New Preparation". The Journal of Organic Chemistry.
9. (2000). "Donor/acceptor organizations and the electron-transfer paradigm for organic reactivity". Elsevier.
10. (1971). "Application of High-potential Quinones. 7. Synthesis of Steroidal Phenanthrenes by Double Methyl Migration". [[Journal of the Chemical Society C: Organic]].
11. (2006). "DDQ-Mediated Direct Cross-Dehydrogenative-Coupling (CDC) between Benzyl Ethers and Simple Ketones". [[Journal of the American Chemical Society]].