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

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2,3-Dichloro-5,6-dicyano-1,4-benzoquinone[1]
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Abbreviations DDQ
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Template:Longitem Template:Chembox Elements/molecular formula
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Appearance yellow to orange powder
Density 1.7g/cm3
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2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the chemical reagent with formula C6Cl2(CN)2O2. This oxidant is useful for the dehydrogenation of alcohols,[3] phenols,[4] and steroid ketones.[5] DDQ decomposes in water, but is stable in aqueous mineral acid.[6]

Preparation

Synthesis of DDQ involves cyanation of chloranil. J. Thiele and F. Günther first reported a 6-step preparation in 1906.[7] 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.[8]

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.[9]

Dehydrogenation

File:DDQ-dehydrogenation.png

Aromatization

File:DDQ aromatization rearrangement.png[10]

Cross-Dehydrogenative Coupling

File:DDQ-oxi-coupling1.png
[11]

Safety

DDQ reacts with water to release highly toxic hydrogen cyanide (HCN).[6]

References

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  1. ↑ 2,3-Dichloro-5,6-dicyano-p-benzoquinone at Sigma-Aldrich
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External links

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