2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ ) is the chemical reagent with formula C 6 Cl 2 (CN) 2 O 2 . This oxidant is useful for the dehydrogenation of alcohols, phenols, and steroid ketones. DDQ decomposes in water, but is stable in aqueous mineral acid .
6-401: 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. The reagent removes pairs of H atoms from organic molecules. The stoichiometry of its action
12-445: A cyanide source. Catalytic cycles are believed to proceed through a standard Pd (0/II) pathway with reductive elimination forging the key C-C bond. Deactivation of Pd(II) with excess cyanide is a common problem. Palladium catalysis conditions for aryl iodides, bromides, and even chlorides have been developed: Nickel-catalyzed cyanations avoid the use of precious metals, and can take advantage of benzyl cyanide or acetonitrile as
18-414: Is illustrated by the conversion of tetralin to naphthalene : 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. DDQ reacts with water to release highly toxic hydrogen cyanide (HCN). Cyanation In organic synthesis , cyanation
24-449: Is the attachment or substitution of a cyanide group on various substrates . Such transformations are high-value because they generate C-C bonds. Furthermore nitriles are versatile functional groups. Typically, alkyl nitriles are formed via S N 1 or S N 2-type cyanation with alkyl electrophiles. Illustrative is the synthesis of benzyl cyanide by the reaction of benzyl chloride and sodium cyanide. In some cases cuprous cyanide
30-408: Is used instead of sodium cyanide. Cyanation of ketones or aldehydes yields the corresponding cyanohydrins , which can be done directly with the cyanide ion (the cyanohydrin reaction ) or by using bisulfite, followed by displacement of sulfite: A related reaction is hydrocyanation , which installs the elements of H-CN. Cyanation of arenes offers access to benzoic acid derivatives, as well as
36-621: The utility of aryl nitriles themselves in as fine chemicals: A variety of mechanistically distinct pathways are known to cyanate arenes: While the classical Rosenmund Von-Braun reaction utilizes stoichiometric copper(I) cyanide as a cyanation source, newer variants have been developed that are catalytic in copper : In addition, palladium-catalyzed cyanations of aryl halides have been extensively explored. Generally, KCN or its less toxic surrogate Zn(CN) 2 are used as nucleophilic cyanide sources. To further diminish toxicity concerns, potassium ferricyanide has also been used as
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