2.3- Dicyano-p-benzoquinone

Marchand and coworkers102 reported a difference in site selectivity between the thermodynamically and kinetically controlled Diels-Alder reactions of cyclopentadiene with 2,3-dicyano-p-benzoquinone (126) (equation 37). Under kinetic conditions, the more reactive double bond of 126 reacted with cyclopentadiene affording 127, whereas the less substituted double bond reacted under thermodynamic conditions affording 128. Both reactions proceeded with complete endo selectivity. These findings were in agreement with ab initio HF/3-21G calculations. 

The asymmetric Diels-Alder cycloadditions of enantiopure (5)-5-(/ -tolylsulfinyl)-1,4-benzoquinones with Dane s diene under thermal and Lewis acid conditions produce tetracyclic quinones after spontaneous elimination of the sulfinyl group.The Diels-Alder reaction of barrelene with o-benzoquinone produces tetracyclo[6.2.2.2 .0 ]tetradeca-9,ll,13-triene-4,5-dione. Under kinetic control, the Diels-Alder cycloaddition of 2,3-dicyano-p-benzoquinone (98) with cyclopentadiene in MeOH produces the single cycloadduct (99) (Scheme 38). ... 

Scheme 2.12 Synthesis of (+)-EBC-23 by using one SAE as the chirality source (DiPT, diisopropyl tartrate PMB, p-methoxybenzyl DMSO, dimethylsulfoxide Si, supersilyl group (see text) LiHMDS, lithium hexamethyidisilazide and DDQ, 5,6-dichloro-2,3-dicyano-p-benzoquinone).

Issa et al. [34] used 2,3-dichloro-5,6-dicyano-p-benzoquinone for the spectropho-tometric determination of primaquine and other antimalarials. The drugs were determined in tablets by a spectrophotometric method based on the reaction with 2.3-d ich loro-5.6-dicyano-p-benzoquinone and measurement of the absorbance at 460 nm. The reaction occurred fastest in methanol and acetonitrile to yield a radical anion, which was detected by electron spin resonance. The color attained its maximum intensity after 5 min and remained stable for at least 1 h. The absorbance versus concentration curve obeyed Beer s law in the concentration range 1-4 mg per 100 mL. The recovery was 99.9-102.6%. 

The 1H—NMR spectrum of 5,6,17,18-tetrahydro[2.2](2,7)phenan-threnopane (48) is compatible with the dihydrophenanthrene units being in an anti position. Dehydrogenation of 48 with 2,3-dichloro-5,6-dicyano-p-benzoquinone in benzene gave [2.2](2,7)phenanthrenophane which, owing to the similarity of its 1H—NMR spectrum to that of 2,7-dimethyl-phenanthrene, is assumed to have its phenanthrene units in the anti position 71>. 

Other dehydrogenation agents include sulfur, selenium dioxide, palladium on charcoal, and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). Some reactions proceed spontaneously. Dehydrogenation also occurred... 

Tetraphenylporphin (H2TPP) was prepared from pyrrole and benzaldehyde (25). The tetraphenylchlorin contamination was oxidized by use of 2,3-dichloro-5,6-dicyano-p-benzoquinone (26). Octaethylporphin (H2-OEP)was prepared by the method of Paine et al.(27) from 3,4-diethyl-2-ethoxy-carbony1-5-methyl-pyrrole (28). Zinc(II)-tetraphenylporphin (ZnTPP) was prepared by refluxing H2TPP and zinc acetate in dimethyl-formamide (29). ZnTPP was dissolved at a concentration of 10 -10 ... 

Hydroxy-l,2,3,4-tetrahydroquinolines 304 were obtained by cyclization of oxime 2,4-dinitrophenyl ethers 303 in the presence of system NaBH3CN/NaH/l,4-dioxane (equation 131) . If the reductive cyclization was followed by oxidation with DDQ (2,3-dichloro-4,5-dicyano-p-benzoquinone) the corresponding 8-hydroxyquinolines 305 were obtained . ... 

Under suitable conditions, further oxidation of the coupled products produces isolable dimer cation radicals. Thus treatment of 9-alkylcarbazoles with lead tetracetate in acetic acid-perchloric acid, or with 2,3-dichloro-5,6-dicyano-p-benzoquinone in acetic acid-perchloric acid, or with tris-(p-bromophenyl)ammoniumyl perchlorate in methylene chloride, or with nitrosonium borofluoride in acetonitrile all gave isolable cation radical perchlorates such as 17. These were reducible with aqueous sodium dithi-onite to the corresponding bicarbazoles the dimer cation radicals could be produced again by reoxidation of the dimer using 2,3-dichloro-5,6-dicyano-p-benzoquinone in acid solution. ... 

The resin-bound 1,3-oxazinium salt 116, obtained by oxidation of 4//-l,3-oxazines 115 with 2,3-dicyano-5,6-dichloro-p-benzoquinone (DDQ), behaved as /3-diketone equivalents and formed pyrazoles 117 through a functionalizing release process on treatment with hydrazines (Scheme 18). When the hydrazines were substituted (R = Me, Ph), the oxazinium salts reacted selectively to afford one regioisomer 117 <2004JC0846>. 

The use of a Lewis acid (e.g., friethylfluoroborate, zinc chloride, stannous chloride, titanium chloride, iron(m)chloride) and other reagents (e.g., iodine, trimethylsilane, trifluoiomethane-sulfonylsilane) have also been recommended. Exhaustive lists of catalysts and conditions can be found in reviews devoted to carbohydrates [5-7], or to general organic chemistry [27,28], However, one can add the new catalyst, which has been introduced for the smooth formation of p-methoxybenzylidene acetals and p-methaxy-phenylmethyl methyl ether [29], namely 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), and has been applied very recently [30] to the synthesis of isopropylidene mixed acetals. 

O. Kjplberg and K. Neumann, Synthesis of acyclic carbohydrate isopropylidene mixed acetals using 2,3-dichioro-5,6-dicyano-p-benzoquinone as a catalyst, Acta Chem. Scand 48 80(1994)... 

A nonconcerted pathway by which A-arylimines react with alkenes to give quinolines has been described (equation 192)690. The reaction takes place at room temperature, in acetonitrile, and is catalyzed by 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) final processing involves bubbling ammonia into the reaction mixture. Yields are low (10-65%) but in many cases only a single product is formed, and purification from starting materials is a relatively simple matter. 

Issa et al. used 2,3-dichloro-5,6-dicyano-p-benzoquinone for the spectro-photometric determination of dipyridamole and other cardiovascular drugs [31]. Aqueous sample solutions are extracted with chloroform, portions of the organic solution are evaporated, and the residues dissolved in 2 mL of acetonitrile. After that, 2 mL of the cited reagent (0.2% solution in acetonitrile) was added, and the solutions diluted to 5 mL with acetonitrile. After 15 min, the absorbance was measured at 430 nm. Calibration graphs are linear in the range 10-50 pg/mL of dipyridamole (molar absorptivity equal to 10,300). The results obtained using this method compared well with those obtained by the official methods. 

AD-mix-P 9-BBN Bn Boc Bz BOM CDI m-CPBA CSA Cy DBU DDQ DEAD DIAD DIBAL-H DIPT DME DMF DMAP DMSO EDC HMPA HOBT KHMDS LDA MEM MOM MoOPH NaHMDS NBS NMM NMO Piv PMB Reagent for Sharpless asymmetric dihydroxylation 9-Borabicyclo[3.3.1 ]nonyl Benzyl t-Butoxy carbonyl Benzoyl B enzyloxy methyl Carbonyldiimidazole m-Chloroperoxybenzoic acid Camphorsulfonic acid Cyclohexyl 1,8 -Diazabicy clo[5.4.0] undec-7-ene 2,3 -Dichloro-5,6-dicyano-p-benzoquinone Diethyl azodicarboxylate Diisopropyl azodicarboxylate Diisobutylaluminum hydride Diisopropyl tartrate Dimethoxyethane A,N-Dimethylformamide 4-Dimethylaminopyridine Dimethyl sulfoxide N-(3-Dimethylaminopropyl)-A -ethylcarbodiimide Hexamethylphosphoramide 1 -Hydroxybenzotriazole Potassium hexamethyldisilazane Lithium diisopropylamide Methoxyethoxymethyl Methoxymethyl Oxidodiperoxymolybdenum(pyridine)(hexamethylphophoramide) Sodium hexamethyldisilazane N - Bromosuccinimide A-Methylmorpholine A-Methylmorpholine A-oxide Pivaloyl /j-Methoxybenzyl... 

Cationic-oxidative polymerization reactions have been developed to synthesize PPS under less severe conditions. For example, PPS has been obtained by a cationic-oxidative polymerization of thiophenol or diphenyl disulfide at room temperature. However, the resulting PPS has a low molecular weight due to premature precipitation. The cationic-oxidative polymerization reaction has been performed electrolytically [109] [Eq. (24)], with Lewis acids [110] [Eq. (25)], with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) [111] [Eq. (26)], and with O2 in the presence of a catalytic amount of VO(acac)2 [112] [Eq. (27)]. 

As phenothiazine is a good electron donor, there are many papers on the interaction of this compound with various acceptors (see Sections III,A,1, and IV,H,1). In most cases, authentical charge-transfer complexes are obtained however, with very strong acceptors, e.g., 2,3-dichloro-5,6-dicyano-p-benzoquinone, (DDQ), there is total transfer of one electron, leading to It is possible that the same... 

When testosterone acetate is refluxed with 2,3-dichloro-5,6-dicyano-p-benzoquinone andp-toluenesulfonic acid in benzene for 5 h, a 60% yield of 6-dehydrotestosterone acetate is obtained [966]. The treatment of an-drost-4-ene-3,17-dione in dioxane with the same quinone and gaseous hydrogen chloride gives a 72% yield of androsta-4,6-diene-3,17-dione [966] (equation 30). 

Some aromatizations are accomplished with agents other than those previously mentioned. Thus tetralin is converted quantitatively into naphthalene by refluxing with 2,3-dix hloro-5,6-dicyano-p-benzoquinone [970], and 1,2,3,4-tetrahydrocarbazoles are transformed into carbazoles in 50-95% yields by refluxing with chloranil in xylene [969], Anhydrous aluminum chloride in refluxing carbon disulfide is used in the preparation of coronene [408]. 

Very selective oxidizing agents suitable for the conversion of primary alcohols into aldehydes are high-potential quinones such as tetrachloro-o-benzoquinone, tetrachloro-p-benzoqninone, and 2,3-dichloro-5,6-dicyano-p-benzoquinone [973]. Such dehydrogenations are carried out in chloroform, carbon tetrachloride, or ethanol, usually under very mild conditions at room temperature or in refluxing ether, and give fair to good yields (equation 216) [973]. 

A general rule is that allylic alcohols are more readily oxidized than saturated secondary alcohols [975], and these, in turn, are more readily oxidized than saturated primary alcohols [681, 741, 1041, 1152], Ceric sulfate [741], ceric ammonium nitrate [741], chlorine [681], sodium hypochlorite [1152], and 2,3-dichloro-5,6-dicyano-p-benzoquinone [975] are successfully used for this purpose (equations 287-289). 

A solution of 0.65 g (0.005 mol) of tetralin and 1.14 g (0.005 mol) of 2,3-dichloro-5,6-dicyano-p-benzoquinone in 5 mL of benzene is refluxed for 45 min, during which period the initidly red solution becomes colorless. A solution of an additional 1.14 g (0.005 mol) of the quinone in 2 mL of benzene is added, and the refluxing is continued for an additional 75 min. After dilution with light petroleum, the solution is filtered, passed through a column of alumina, and evaporated to give 0.42 g (70%) of naphthalene, mp 79-80 °C. The petroleum-insoluble residue yields 0.7 g (61%) of colorless 2,3-dichloro-5,6-dicyanohydroquinone, mp 263 °C (dec), after crystallization from aqueous ethanol. 

---