O-Chloranil

Tricarbonyl[t/M-(ethoxycarbonyl)-l//-azepine]iron(0) (30) with the 2-oxyallyl cation derived from 2,4-dibromo-2,4-dimethylpentan-3-one and nonacarbonyldiiron(O) yields a mixture of adducts which, after oxidative decomplexation with tetrachloro-l,2-benzoquinone (o-chloranil), affords the tetrahydrofuro[2,3-A)azcpine derivative 33 and the 3-substituted 1H-azepine-l-carboxylate 34.227... 

Cycloaddition-cyclorevcrsion reaction of 9-oxabicyclo[6.1.0]nona-2,4,6-triene (6) with 3,6-diphenyl-1,2,4,5-tetrazine followed by dehydrogenation with tetrachloro-1,2-benzoquinone (o-chloranil) yields the annulated oxonin 7.8... 

Note It is reported that the use of chlorobenzene as solvent is essential when the reagent is to be used to detect aromatic amines [1]. In the case of steroids, penicillins, diuretics and alkaloids the reaction should be accelerated and intensified by spraying afterwards with dimethylsulfoxide (DMSO) or dimethylformamide (DMF), indeed this step makes it possible to detect some substances when this would not otherwise be possible [5,9-11] this latter treatment can, like heating, cause color changes [5,9]. Penicillins and diuretics only exhibit weak reactions if not treated afterwards with DMF [10, 11]. Steroids alone also yield colored derivatives with DMSO [9]. Tlreatment afterwards with diluted sulfuric acid (c = 2 mol/L) also leads to an improvement in detection sensitivity in the case of a range of alkaloids. In the case of pyrrolizidine alkaloids it is possible to use o-chloranil as an alternative detection reagent however, in this case it is recommended that the plate be treated afterwards with a solution of 2 g 4-(dimethyl-amino)-benzaldehyde and 2 ml boron trifluoride etherate in 100 ml anhydrous ethanol because otherwise the colors initially produced with o-chloranil rapidly fade [12]. 

Pd2(dba)3/l,4-bis(diphenylphosphino)butane (DPPB) in the presence of 2-mercaptobenzoic acid <95TL1267>. The Af-allylindolines can be easily oxidized to the corresponding indoles at room temperature with o-chloranil. Additionally, Al-allylanilines were also found to undergo aromatic 3-aza-Cope rearrangements in the presence of Zeolite catalysts to give indoline derivatives as the major product <96TL5281>. 

Following a similar protocol, novel hexacoordinated phosphate anions 19 to 22 bearing two different dioxo ligands could be simply prepared as their di-methylammonium salts from the reaction of tetrachlorocatechol derived phos-phoramidite 23 with a variety of symmetrical diones other than o-chloranil (a-diketones or orf/zo-quinones) and subsequent addition of tetrachlorocatechol to the corresponding phosphorane 24 (Scheme 3) [42]. 

Studying the reactivity of lo, 2a -diphosphete 56 with o-chloranil, Bertrand and coworkers reported the synthesis of zwitterionic 57 in which the two phosphorus atoms are directly linked by a a bond (Scheme 13). Structural details of 57 were further obtained through a X-ray crystallographic analysis [70]. 

The structure of the o-chloranil O-adduct 91 was determined by single crystal X-ray (Figure 3.12). 

Figure 3.12 Single crystal X-ray structure of O-adduct with o-chloranil.

Phosphorus heterocycles 246 derived from hydroxyphenyl benzimidazole and aminophenyl benzimidazole undergo oxidative cycloaddition with 3,5-di-/fV/-butyl-l, 2-bcnzoquinonc to give a mixture of 247 and 248 (Equation 60) <2004HAC307, 2004HAC321>. Oxidative addition of ort o-chloranil to bis- and tetrakis-cyclodiphos-phazene compounds gives bis- and tetrakis-spirophosphoranes, for example, 41 (Equation 61). 

Figure 5. Synthesis of 1,2- and 3,4-dibenzoyloxy-l,2,3,4-tetra hydrobenz(a)anthracene from BA by Method II (22.). Reagents (i) Li,NH (ii) NaOMe, DMSO (iii) AgOBz, I2 (iv) o-chloranil.

An alternative new synthetic approach to chrysene 1,2-dihydro-diol based on Method IV has recently been developed (60). This method (Figure 12) entails synthesis of 2-chrysenol via alkylation of 1-1ithio-2,5-dimethoxy-1,4-cyclohexadiene with 2-(1-naphthyl) e-thyl bromide followed by mild acid treatment to ge nerate the diketone 12. Acid-catalyzed cyclization of 12 gave the unsaturated tetracyclic ketone 13 which was transformed to 2-chrysenol via dehydrogenation of its enol acetate with o-chloranil followed by hydrolysis. Oxidation of 2-chrysenol with Fremy s salt gave chrysene... 

Ether cleavage of 4-heptyl-3-methylveratrole 121 using boron tribromide affords 4-heptyl-3-methylcatechol 122 (Scheme 38). Oxidation of the catechol 122 with o-chloranil to 4-heptyl-3-methyl-l,2-benzoquinone 123 and subsequent immediate addition of aniline leads to 5-anilino-4-heptyl-3-methyl-l,2-benzo-quinone 124. Unlike the very labile disubstituted ort/zo-quinone 123, compound 124 is stable and can be isolated. Palladium(II)-mediated oxidative cyclization of the anilino-l,2-benzoquinone 124 provides carbazoquinocin C 51. 

Fig. 6. Relation between dark conductivity and concentration of doping compounds log Od = / (log nacceptor/ndye). (I) phthalocyanine-(-o-chloranil (2) poly-N-vinylcarbazole + o-chloranil...

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