2.6- Dichloro-3-methyl-1,4-benzoquinone

METHYL KETONES AUyltrimethyl-silane, Bis(acetonitrilo)chloronitro-palladium (11). Dicarb ony lbis( triphenyl-phosphine)nickel. Dichloro-dicyano-benzoquinone. Hydrogen peroxide-Palladium acetate. Meldrum s acid. Palladium r-butyl peroxide trilluoro-acctate. Palladium tl) chloride. 

Figure 3. pH dependence of for the electron transfer from cw-[Et2Co(bpy)2] to p-benzoqui-none derivatives in H20-EtOH (5 1 v/v) at 298 K 2,6-dichloro-p-benzoquinone (O) 2,5-dichloro-p-benzoquinone ( ) chloro-p-benzoquinone (A) p-benzoquinone (A) methyl-p-benzoquinone ( ) and 2,6-dimethyl-p-benzoquinone ( ). 

On spraying with 2,6-dichloro-p-benzoquinone-4-chloroimine, ceric sulfate reagent (Seher, 1960, 1961) and especially with antimony penta-chloride (BoUiger, 1962), the tocopherols give different colors which vary also with the adsorbant, as shown in Table IX and Figs. 7 and 8. The reaction with antimony pentachloride (20% in chloroform) depends on the number and position of the methyl gi-oup on the benzene ring and on the nature of the side chain. These color complexes are not stable, however. 

Dissolve 0 5 g of lotion containing 0 2 per cent of chlorocresol in sufficient 72 per cent ethanol (prepared from industrial methylated spirit that has been refluxed for four hours over potassium hydroxide and distilled) to make exactly 50 ml. Shake well, chill in ice-water and filter. Pipette 10 ml of the filtrate into a 20-ml graduated flask and dilute to 12 ml with the 72 per cent ethanol. Add 2 ml of a 0 012 per cent solution of 2,6-dichloro-p-benzoquinone-4-chloroimine in 95 per cent ethanol (refluxed and distilled as above) and 2 ml of a 1 5 per cent aqueous borax solution, mixing after each addition. Allow to stand in the dark for one hour and then dilute to volume with the 72 per cent ethanol. Mix and measure the extinction at 650 m/U in a 2-cm cell subtract the value of a reagent blank and read off the amount of chlorocresol from a calibration curve. 

The current-potential curves of the catalytic oxidation current mediated by the mixed-in mediators depend on the electrode reaction properties of the mediator used, as theory has predicted those which gave reversible cyclic voltammograms, such as, 1,2-naphthoquinone and 2,6-dichloro-p-benzoquinone produced reversible catalytic current-potential curves, as shown in Figure 7, whereas those which gave quasi-reversible or irreversible cyclic voltammograms, such as BQ and 2-methyl-p-benzoquinone, gave quasi- or irreversible drawn-out waves, as seen in Figure 1. The half-wave potential of the catalytic current nearly coincided with the mid-potential for the former "reversible compounds, whereas it was shifted to more positive potential than the mid-potential for the latter. In the same way, the enzyme kinetics should also influence the dependence of the catalytic current on the electrode potential. 

Dichloro- 2,6-Dichloro-3-methyl- 2,3,6-Trichloro- 2,6-Dibromo-1,4-benzoquinone, 4-benzoquinone 1,4-benzoquinone 1,4-benzoquinone... 

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 ... 

Treatment of veratrole (191) with excess of 2,5-dichloro- (192) or 2,6-dichloro-1,4-benzoquinone in 70% sulfuric acid yields dibenzofurans and other products. Thus 2,5-dichloro-1,4-benzoquinone (192, Scheme 49) affords the dibenzofuran 193, the diarylquinone 194 and the triphenylene 195. The quinol formed by acid-catalyzed addition of veratrole (191) to the quinone 192 is presumably oxidized to the arylquinone 196, which can form the dibenzofuran 193 or undergo further arylation. The quinone 196 is also available by arylation of 2,5-dichloro-1,4-benzoquinone (192) with 3,4-di-methoxybenzenediazonium chloride in buffered solution. On treatment with 70% sulfuric acid, the arylquinone 196 affords the dibenzofuran 193 (88%). The cyclization can also be effected photochemically. The aryl-quinones available by treatment of 2,5- and 2,6-dichloro-1,4-benzoquinones with buffered solutions of diazotized 4-methoxy-3-methyl- and 3-methoxy-4-methylaniline have been cyclized to 2-dibenzofuranols by the agency of aluminum chloride in hot benzene. ... 

Since the publication of CHEC-II(1996), there have been very few examples related to the reactivity of substituents attached to ring carbon atoms. One case involves the reaction of 3-benzylidene-2,3-dihydro-2-methyl-l,2-benzothiazin-4-one 1,1-dioxide 163 with the alkylidenephosphorane derived from salt 164 forming the tricyclic-fused ring compound 165 (Scheme 20) <1996J(P1)2541>. This material 165 was oxidized with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) affording the biphenyl 166. Ring-opened product 167 was produced from 165 upon exposure to />-toluene-sulfonic acid and heat. 

Hurd-Mori reaction on hydrazone 147 produced methyl thieno[3,4-r/ -l,2,3-thiadiazole-6-carboxylate 148 along with methyl thieno[3,2-r7 -l,2,3-thiadiazole-5-carboxylate 135 and methyl 5,6-dihydrothieno[3,2-r7 -l,2,3-thiadiazole-5-carboxylate 149 in a ratio of 1 2.6 0.5 (72% combined yield). Conversion of compound 149 to the fully aromatized 135 is accomplished by treatment with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) in refluxing benzene for 10 days (Scheme 15). A modified reaction mechanism for the Hurd-Mori reaction is also presented here <1998H(48)259>. 

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. 

AT-Formylnor-reticuline, on treatment with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone in methanol, is oxidized to the 4-methoxy-compound (35), which can be cyclized to N-norbisnorargemonine (36) (converted by N- and O-methylation into argemonine) by mineral acid or to the isopavine N-formyl-northalidine (37) by treatment with methanesulphonic acid in acetonitrile. The N-formyl compounds can be reduced to AT-methyl by borane or converted into the secondary bases by hydrazinolysis.69... 

Dichloro-5,6-dicyano-l,4-benzoquinone Trimethylchlorosilane Methyl magnesium bromide Hydrochloric acid... 

In parallel studies to the ruthenium-based work, Ward and co-workers have also shown that PIFA (Scheme 44) [122, 128] and 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) (Scheme 45) [122, 129, 130] are effective reagents for coupling the phenolic precursors 185a,b. Yields are generally lower than in the fully methylated case (spirodienone products 188 can be formed when a hydroxyl group is present at the para position of the 2-benzyl group of 185a) and unbiased mixtures of atropisomers 186/187 and 189/190 are obtained. 

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... 

Ac, acetyl AIBN, azobis(isobutanonitrile) All, allyl AR, aryl Bn, benzyl f-BOC, ferf-butoxycarbonyl Bu, Butyl Bz, benzoyl CAN, ceric ammonium nitrate Cbz, benzyloxycarbonyl m-CPBA, m-chloroperoxybenzoic acid DAST, diethylaminosulfur trifluoride DBU, l,8-diazabicyclo[5.4.0]undec-7-ene DCC, /V. /V - d i eye I oh e x y I c ar bo -diimide DCM, dichloromethyl DCMME, dichloromethyl methyl ether DDQ, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone DEAD, diethyl azodicarboxylate l-(+)-DET, L-(+)-diethyl tartrate l-DIPT, L-diisopropyl tartrate d-DIPT, D-diisopropyl tartrate DMAP, 4-dimethylaminopyridine DME, 1,2-dimethoxyethane DMF, /V./V-dimethylformamide DMP, 2,2-dimethoxypropane Et, ethyl Im, imidazole KHMDS, potassium hexamethyldisilazane Me, methyl Me2SO, dimethyl sulfoxide MOM, methoxymethyl MOMC1, methoxymethyl chloride Ms, methylsulfonyl MS, molecular sieves NBS, N-bromosuccinimide NIS, /V-iodosuccinimide NMO, /V-methylmorpho-line N-oxide PCC, pyridinium chlorochromate Ph, phenyl PMB, / -methoxvbenzyl PPTs, pyridiniump-toluenesulfonate i-Pr, isopropyl Py, pyridine rt, room temperature TBAF, tetrabutylammonium fluoride TBS, ferf-butyl dimethylsilyl TBDMSC1, f-butylchlorodimethylsilane Tf, trifhioromethylsulfonyl Tf20, trifluoromethylsulfonic anhydride TFA, trifluoroacetic acid THF, tetrahydrofuran TMS, trimethylsilyl TPAP, tetra-n-propylammonium perruthenate / -TsOH. / -toluenesulfonic acid... 

Two additional Step 2 derivatives, methyl 2-benzylthio-6-phenylcyclohex-2-ene carboxylate and methyl 2-benzylthio-6-phenylcyclohex-l-ene carboxylate were also prepared by the author and aromatized using 2,3-dichloro-5,6-dicyano-benzoquinone and chlorine gas and are described. 

Abbreviations Ac acetyl Bn benzyl BSP 1-benzenesulfinyl piperidine BTIB bis(trifluoroacetoxy)iodobenzene DAST (diethylamino)sulfur trifluoride DDQ 2,3-dichloro-5,6-dicyano-/)-benzoquinone DMDO dimethyldioxirane DMTSF dimethyl(methylthio)sulfonium tetrafluoroborate DMTST dimethyl(methylthio)sulfonium triflate DTBMP 2,6-Ai-tert-butyl-4-methylpyridine DTBP 2,6-di-tert-butylpyridine DTBPl 2,6-di-tert-butylpyridinium iodide FDCPT l-fluoro-2,6-dichloropyridinium triflate FTMPT l-fluoro-2,4,6-trimethylpyridinium triflate IDCP iodonium dicollidine perchlorate IDCT idonium dicollidine triflate LPTS 2,6-lutidinium p-toluenesulfonate LTMP lithium tetramethylpiperidide Me methyl MPBT S-(4-methoxyphenyl) benzenethiosulflnate NBS A-bromosuccinimide NIS A-iodosuccinimide NlSac A-iodosaccharin PPTS pyridinium p-toluenesulfonate TBPA tris(4-bromophenyl)ammoniumyl hexachloroantimonate Tf trifluoromethanesulfonyl TMTSB methyl-bis(methylthio)sulfonium hexachloroantimonate TMU tetramethylurea Tr trityl TTBP 2,4,6-tri-tert-butylpyrimidine. 

Abbreviations Ac acetyl AIBN azobisisobutyronitrile All allyl Bn benzyl Bz benzoyl ClAc chloroacetyl DAST diethylaminosulfur trifluoride DBU l,8-diazabicyclo[5.4.0]-undec-7-ene DDQ 2,3-dichloro-5,6-dicyano-/)-benzoquinone DMDO dimethyldioxirane DMTST dimethyl(methylthio)sulfonium trifluoromethanesulfonate Fmoc 9-fluorenyl-methoxycarbonyl HDTC hydrazine dithiocarboxylate IDCP iodonium di-collidine perchlorate Lev levulinoyl MBz 4-methylbenzoyl Me methyl MEK methyl ethyl ketone MP 4-methoxyphenyl NBS iV-bromosuccinimide NIS A-iodosuccinimide Pent n-pentenyl Pfp pentafluorophenyl Ph phenyl Phth phthaloyl Piv pivaloyl PMB 4-methoxybenzyl TBAF tetrabutylammonium fluoride TBDMS tcrt-butyldimethylsilyl TBDPS tert-butyldiphenylsilyl TCA trichloroacetyl TES triethylsilyl Tf trifluoromethanesulfonyl TMS trimethylsilyl Tol 4-methylphenyl Tr trityl Troc 2,2,2-trichloroethoxycarbonyl Ts tosyl. 

Aromatization (see also Dehydrogenation) 2,3-Dichloro-S,6 1icyano-l,4-benzoquinone. Aryl bromide ArOH Methyl borate. 

Electron-transfer Initiation. Highly electron-rich monomers like A-vinylcarbazole can be polymerized readily by powerful electron acceptors such as chloranil, tetracyanoethylene, and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). Recently the killing of polymerizations at low conversion by addition of methanol has shown that the ion radicals initially formed combine to give a zwitterion in the case of DDQ with methyl vinyl ether (Scheme 6), although to what extent this structure is maintained throughout polymerization is not certain. 

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