Dichlorodicyanobenzoquinone

In comparison with manganese dioxide, the DDQ reagent has several advantages for the oxidation of allylic alcohols. The quinone method is more reproducible only one equivalent of oxidant need be added and generally fewer side reactions are observed. On the other hand, the workup of DDQ reactions often requires chromatography and in the simpler cases lower isolated yields may be realized. 

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This order was chosen so that DDQ (dichlorodicyanobenzoquinone) treatment would not oxidize a dep otected allylic alcohol at C.73, and so that the C.47 hemiketal would still be protected (as the ketal) during basic hydrolysis (step 3). 

The first successful transformation of protoberberines to benzo[c]-phenanthridines was reported by Onda et al. (122,123). Irradiation of the enamines 200 and 195, the Hofmann degradation products of the corresponding protoberberines, in benzene afforded the initial photoproducts 201, which immediately rearranged to the tetrahydrobenzo[c]phenanthridines 202 in 70% yield (Scheme 37). Dehydrogenation of 202 afforded dihydro-chelerythrine (203) and dihydrosanguinarine (204), which were further oxidized with dichlorodicyanobenzoquinone (DDQ) to yield chelerythrine (205) and sanguinarine (206), respectively. 

Donor/acceptor association and the electron-transfer paradigm form the unifying theme for the C—C bond cleavage of various benzpinacols and diary-lethane-like donors in the presence of different electron acceptors (such as chloranil (CA), dichlorodicyanobenzoquinone (DDQ), tetracyanobenzene (TCNB), triphenylpyrylium (TPP+), methyl viologen, nitrosonium cation, etc.). Scheme 13 reminds us how this is achieved by either CT photolysis of the D/A pair or via diffusional quenching of the excited electron acceptor A by the electron donor D. 

Condensation of DAMN with orthoformates (Section IV,B) under mild conditions yields the intermediate alkoxyimines 16 (50USP2534331 74JOC2341). Oxidation of 16 with dichlorodicyanobenzoquinone or N-hro-mosuccinimide gives the corresponding 2-alkoxy-4,5-dicyanoimidazole (17) (Scheme 8) (73USP3778446 74JOC2341). 

Compound 352 was also obtained by dehydrogenation of an appropriate dihydro derivative with dichlorodicyanobenzoquinone.335... 

XI. Selective Oxidation of Allylic Alcohols / 244 Manganese dioxide / 244 Dichlorodicyanobenzoquinone / 247 Nickel peroxide / 248... 

Direct oxidation of chromans to chromenes can be achieved using a high potential quinone chloranil and dichlorodicyanobenzoquinone are suitable. Much attention has been devoted to the latter reagent. 

In contrast to the efficient copolymerization reaction described above, reactions of la with strongly electron-deficient olefins and acetylenes (dicyanoacetylene, dimethyl acetylenedicarboxylate, tetracyanoethylene and dichlorodicyanobenzoquinone) produce... 

A benzolog of 1 //-naphtho[o/]azepine-2-one 506 is obtained by cy-clization of l-(2 -amino)phenyl-8-methoxycarbony [naphthalene 505 (71AJC835). The reduction of azepinone 506 to azepine 507, followed by dehydrogenation with dichlorodicyanobenzoquinone (DDBQ) leads to benzo[/]naphtho[crf]azepine 508. The latter compound easily adds water, alcohol, or amines to a C=N bond, resulting in adducts 509, whereas treatment with perchloric acid gives rise to perchlorate 510 (71AJC835). 

Alkali chlorites, NaCl20, in the presence of cuprous salts, can also be used for this oxidation. Oxidation of thioureas with dichlorodicyanobenzoquinone in the presence of sodium hydroxide also affords carbodiimides. Reaction of dialkylthioureas with sodium amide in refluxing toluene affords carbodiimides 25. The use of sodium hydride instead of sodium amide gives higher yields. 

In earlier literature there are reports of the formation of perhalides on treatment of phenothiazine with bromine and iodine these are now considered to be charge-transfer complexes. The phenothiazine component normally acts as a donor and the electronegative halogens as acceptors, but here total transfer of electrons occurs and the phenothiazine is oxidized. Phenothiazine and 3,7-dimethylpheno-thiazine behave similarly in the presence of strong organic acceptors, like dicyanobenzoquinone and dichlorodicyanobenzoquinone. ... 

Benzo-fused azoniaazulenes were also reported. o-Benzylphenyl azide 260 (92%) was obtained by diazotization of 259 followed by treatment with sodium azide. Decomposition of the azide 260 at 190°C gave azepinoindole 261, which was hydrolyzed to afford dihydroazepinoindolone 262 (90%). Dehydrogenation of262 with dichlorodicyanobenzoquinone yielded azepi-... 

New applications of dichlorodicyanobenzoquinone (DDQ) for the dehydrogenation of ketones include the conversion of a 4,7-dien-3-one into the 4,6,8(14)-trienone, which is further dehydrogenated to the l,4,6,8(14)-tetraenone with acidic catalysis.The dehydrogenation of a 4-en-6-one with DDQ affords the 2,4-dien-6-one. Selective 1,2-dehydrogenation of 5a-cholestan-3-one has been achieved with palladium acetylacetonate and oxygen.Possible alternative mechanisms are discussed. 

Sammes and co-workers (314) have also shown that some piperazine-2,5-diones (89) react with an excess of triethyloxonium iluoroborate to give a mixture of cis-and rra/is-2,5-diethoxy-3,6-dihydropyrazines (90) which can be oxidized with dichlorodicyanobenzoquinone (DDQ) to 2,5-diethoxypyrazines (91) in high yield. Many similar oxidations of dihydropyrazines have recently been described (314a). 

Naphtho[l,2-6]tellurophene was obtained by dehydrogenation of 4,5-dihydronaphtho-[1,2-/)]tellurophene (see tellurophene, p. 733) with dichlorodicyanobenzoquinone". ... 

From the reaction with dimethyl fumarate, the 1 1 cycloadduct 471 was also isolated. On oxidation with 2,3,5,6-dichlorodicyanobenzoquinone in boiling dioxane, dihydropyrrolo[l,2-fl]quinazoline-l-carboxylate (473) afforded the pyrrolo(l,2-a]quinazoline-l-carboxylate 474. The latter product also resulted when the acid 475 was treated with an excess of ethyl propiolate and acetic anhydride in boiling xylene. The reaction of the thiazo[3,2-c]quinazoline 469 with dimethyl acetylenedicarboxylate in boiling toluene led to the pyrimido[l,2-a]quinazolinone 472. 

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