DDQ, dichlorodicyanoquinone

In order to prepare a radical cation in solution, an electron must in some way be abstracted from a normal neutral molecule. There are three main ways in which this can be achieved. In the first, the electron is transferred to a powerful electron acceptor such as a metal in a high valence state (e.g., Mn", Co ") or a high-energy quinone (e.g., DDQ, dichlorodicyanoquinone). In the second, the electron is transferred to the positive electrode (anode) in... 

Oxazoles are prepared from tryptophan loaded Wang resin 53 (Scheme 9.7) The deprotected N-terminal was condensed with carboxylic acids 54 or carboxylic acid anhydrides 55 to give Af-acetyltryptophans 56. The key step involved oxidation of 56 with 2 equiv of DDQ (dichlorodicyanoquinone) in THF H20 (9 1) at room temperature for 15 min, producing the key intermediate 57. Compound 57 underwent cyclocondensation in the presence of triethylamine, CCLj, and triphenylphosphine in acetonitrile at room temperature for 2h to afford the oxazole 58. After cleavage from the resin with 20% TFA in DCM, esterification was carried out using TMS diazomethane to give the final product 59. 

Several methoxy-substituted benzyl ethers have been prepared and used as protective groups. Their utility lies in the fact that they are more readily cleaved oxidatively than the unsubStituted benzyl ethers. The table below gives the relative rates of cleavage with dichlorodicyanoquinone (DDQ). ... 

Dichlorodicyanoquinone (DDQ), CH2CI2, H2O, 40 min, it, 84-93% yield.This method does not cleave simple benzyl ethers. This method was found effective in the presence of a boronate. The following groups are stable to these conditions ketones, epoxides, alkenes, acetonides, to-sylates, MOM ethers, THP ethers, acetates, benzyloxymethyl (BOM) ethers, and TBDMS ethers. 

Benzyl groups having 4-methoxy (PMB) or 3,5-dimethoxy (DMB) substituents can be removed oxidatively by dichlorodicyanoquinone (DDQ).181 These reactions presumably proceed through a benzylic cation and the methoxy substituent is necessary to facilitate the oxidation. 

N-Methyl- and N-phenyl-2-vinylpyrroles 20a,b react with DMAD at reflux temperature in chloroform to give, in moderate yields, the dihydroindoles 22 via a 1,3-H shift from the Diels-Alder intermediate 21 (55-75%) (80JOC4515). These adducts were readily converted into the corresponding indoles 23 with Dichlorodicyanoquinone (DDQ). 2-Vinyl-pyrrole failed to give [4 + 2]-cycloadducts with acetylenic esters (80JOC4515). Spectroscopic analysis of the product mixtures indicated the presence of polymeric compounds resulting from Michael addition reactions. 

The mechanism of dehydrogenation of aromatic compounds with dichlorodicyanoquinone (DDQ) is shown in Scheme 7,32. 

Schiff bases (14), which are formed by reaction between DAMN and appropriate carbonyl reagents, are oxidatively cyclized to give a variety of 2-substituted 4,5-dicyanoimidazoles (15) (Scheme 2.1.5). Although dichlorodicyanoquinone (DDQ) or diaminosuccinonitrilc (DISN) have been used frequently to achieve the oxidative cyclization, long reaction times (17 h to 4 days under reflux) are a disadvantage, and N-chlorosuccinimide (NCS) under basic conditions is more convenient in many cases. The Schiff bases are best formed from aromatic aldehydes, but aliphatic aldehydes and ketones, ketoesters, orthoesters, amides, imidates and cyanogen chloride have all been used [15, 41-49J. 

Polyvinylferrocene, 14, polyferrocenylene, 15, and polyethynylferro-cene, 16, were each oxidized by dichlorodicyanoquinone (DDQ), iodine, and TCNQ to give a polymer series e.g. Equations 1, 2, and 3) with a range of Fe(II)/Fe(III) ratios. The amount of oxidation was controlled by the reactant stoichiometry, and Fe(II)/Fe(III) ratios were firmly established by both elemental analyses and by Mossbauer spectroscopy (21). In each case, the isomer shifts and quadrupole splittings were about 0.78 and 0.0-0.2 for ferricenium units. Each DDQ molecule incorporated into the polysalts was reduced to DDQ" as was indicated by the absence of the 1680 cm" vco of DDQ and the presence of the 1590 cm" vco of DDQ" (21). The Fe(II)/Fe(III) ratios from elemental analyses agreed within 5% with those determined by Mossbauer spectroscopy. All mixed valence polymers were blue-black or black because of the ferricenium 620 nm 2 / transition. Polysalts of 15... 

The cycloaddition of l,3,4-oxadiazin-6-ones 97 (R =Ph, Pr R = Ar, C02Me) to cyclopentadiene in the presence of TFA leads to the formation of regioisomeric dihydro-a-pyrones 106 and 107 <1998CC2387>. The dehydrogenation of 106 and 107 with dichlorodicyanoquinone (DDQ) affords the a-pyrones 108 and 109. The latter are converted to cyclopenta[f]pyrans 110 with diisobutylaluminium hydride (DIBAL-H) (Scheme 13). 

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