2.3- Dichloro-4,5-dicyanobenzoquinone DDQ

Reaction of the 3-substituted l,2,3-triazolo[4,5-d]pyrimidines (183) with one equivalent of a Grignard reagent in THF afforded the dihydro compounds 185 after hydrolysis of the intermediates 184. Aromatization of 185 by oxidation with potassium ferricyanide (79CPB3176) or with 2,3-dichloro-4,5-dicyanobenzoquinone (DDQ) (89CPB1731) gave the 3-substituted 7-alkyltriazolopyrimidines 186. Replacement of the methylsul-... 

Similar reactions occur with toluene (35), which with Cs-K-Na alloy in THF at about -45°C gives 116 which with water yields 46% of 117. Dehydrogenation of 117 with 2,3-dichloro-4,5-dicyanobenzoquinone (DDQ) gives dimethylbiphenyl, which contains more than 99% of 3,3 -dimethylbiphenyl 118. 

Figure 5. Electropotential scale for reagents and guests relative to Li/Li. DDQ is 2,3-dichloro-4,5-dicyanobenzoquinone bzph, benzophenone naph, naphthalene (after ref. 21).

Since hot pepper is important for the food and the pharmaceutical industries, a range of different methods have been developed for the analysis of capsaicinoids in plant material and finished products. The separation of CPS (la) and nonivamide (11) is especially challenging, since these compounds have similar behavior in many chromatographic conditions. Since synthetic nonivamide is the most common adulterant of capsicum oleoresin, various strategies have been suggested to overcome this problem. Capillary GC does not require previous derivatization of capsaicinoids, but its separatory power seems lower than that of HPLC, currently the most popular technique for the quantization of capsaicinoids. GC is, however, the method of choice for the analysis of the acyl moieties of capsaicinoids as methyl esters. These can be directly produced from capsaicinoids by oxidative N-dealkylation with DDQ (2,3-dichloro-5,6-dicyanobenzoquinone), followed by alcoholysis of the resulting amides with methanol in the presence of an acidic resin (Scheme 4.4) [41]. 

Cbz Cp DABCO DBU DDQ (DHQD)2CLB (DHQD)2PYR DMF DME DMPU DMSO Et Fmoc HMPA ia KHMDS LDA LiHMDS Me MEM Ms NaHMDS Ph Piv PMB Pr Py (saltmen)Mn(N) benzyloxy carbonyl p 5 -cyclopentadienyl l,4-diazabicyclo[2.2.2]octane l,8-diazabicyclo[5.4.0]undec-7-ene 2,3 -dichloro-5,6-dicyanobenzoquinone dihydroquinidinyl p-chlorobenzoale (see Chart 1) dihydroquinidinyl pyrimidine (see Chart 1) dimethylformamide dimethoxyethane l,3-dimethyl-3,4,5,6-tetrahydro-2(l//)-pyrimidinone dimethylsulfoxide ethyl 9-fluorenylmethoxy carbonyl hexamethylphosphoric triamide inverse addition potassium hexamethyldisilazide lithium diisopropylamide lithium hexamethyldisilazide methyl (2-methoxy ethoxy )methyl methanesulfonyl sodium hexamethyldisilazide phenyl pivaloyl p -methoxy benzyl propyl pyridine nitrido[A,A/-(l,l,2,2-tetramethyl) bis(salicylideneaminato)]manganese (see Chart 1)... 

Dihydropyrimido[4,5-t/]pyridazines 1 (accessible by the reaction of pyrimido[4,5-z/]-pyridazines with organometallic compounds62 or by the photochemical addition of alcohols 63 see Section 7.4.6.2.) are oxidized to the fully conjugated pyrimido[4,5-<7]pyndazine system 2 by 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) or potassium hexacyanoferrate(III).61... 

A two-step sequence involving thermal [4+2] cycloaddition followed by dehydrogenation using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) has been used for the synthesis of diethyl esters of naphthalene and anthracene dicarboxylates in good yields (Scheme 16.19) [20]. 

The dinitrile precursors for p-tetra- and p-octatrifluoromethylphlhalocyanines [MPcP(CF3)4] and [MPci (CF3)g] (Scheme 24) were obtained [69] starting from the mono(bis)trifluoromethyl substituted acetylenes 88a,b and 2,3-dimetylbutadiene 89 which easily give the Diels-Alder products 90a,b. These adducts were converted quantitatively upon dehydrogenation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to o-xylene derivatives 91a,b. Their oxidation Cr03 in a mixture of acetic and sulfuric acids affords the phthalic acids 91a,b (yield ca. 80 %) which were converted to dinitriles 96a,b and diiminoimides 97a,b in a common way through intermediate anhydrides 93a,b, imides 94a,b, diamides 95a,b. 

Preparation by oxidation of (3,5-di-tert-butyl-4-hydroxyphenyl)phenylcarbinol with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in dioxane at r.t. for 15 min (95%) [153]. 

A metal-free dehydrogenative coupling approach was used by Wan for the generation of a-aminophosphonates using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as the oxidizing agent (Seheme 4.109) [180]. Similar to other studies, tetrahydroisoquinolines were selected by the authors as the representative substrates for the reaction along with several secondary phosphites. The conditions were mild, and moderate to excellent yields... 

V vs. SCE in MeCN (Pt electrode 0.1 M [n-Bu4N][C104]). DDQ = 2,3-dichloro-5,6-dicyanobenzoquinone, TCNQ = 7,7,8,8-tetracyano-p-quinodimethane, TCNQF4 = perfluoro-7,7,8,8-tetracya-no-p-quinodimethane, TCNQ(CN)4 = percyano-7,7, 8,8-tetracyano-p-quinoimethane, TCNE = tetracyanoethene. [Q1 has a... 

This concept-the organocatalyzed a-alkylahon of enoUzable aldehydes with stabiUzed carbocahons-has been extended to the deployment of several other substrates and reachons condihons. Oxidation in these processes was achieved by means of equimolar amounts of DDQ (2,3-dichloro-5,6-dicyanobenzoquinone). Selected results of this inveshgahon are depicted in Scheme 4.14 [44]. For a combinahon of organocatalysis and electrochemistry using these substrates see Reference [45],... 

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