With o-chloranil

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>. 

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]. 

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

Table 4. AE values of phthalocyanine doped with o-chloranil...

The simple benzoannulated derivatives (38b and c) and the hydrocarbon model (38a) were synthesized from cycloadducts 37 by a two-step sequence entailing thermal extrusion of COa followed by juncture dehydrogenation with o-chloranil.43... 

Some 2-aminopyridine derivatives (107 and 108) were formed, also. Of the Schiff bases, only the benzaldehyde derivative reacted, yielding the 4-hydroxypyrido[l,2-a]pyrimidine (109), which was then oxidized with o-chloranil to the 4-oxo compound. 

In 1956, Braude et al.92 showed that treatment of allylic, benzylic and propargylic alcohols with o-chloranil (tetrachloro-l,2-benzoquinone) (82) provided the corresponding aldehydes and ketones. Under the mild conditions employed, involving room temperature or refluxing ether, saturated alcohols remained unaffected. 

Scheme 22)87 The intramolecular 4 + 2-cycloaddition of ynamides with conjugated enynes produces substituted indolines that can be oxidized to indoles with o-chloranil.88 The double Diels-Alder cycloaddition of the linear conjugated tetraene... 

The oxidation of compound (233) with o-chloranil in CHC13 gave the benzodioxane adduct (234) along with a minor amount of the desired product (235). Extended treatment with o-chloranil or reaction of adduct (234) with o-chloranil gave compound (236) (Scheme 22) (79JOC2518). 

Only a few examples of a Diels-Alder type reaction of the valence tautomeric ketene of mesoionic 1,3-dithiolones are known. Thus the reactions of differently substituted mesoionic compounds (2) with o-chloranil give the unusual adducts (142), derived via [4 + 2] cycloaddition to the non-detectable valence tautomeric ketene (141) which is in equilibrium with (2). The reaction rate depends upon the nature of the substituents, for example substituents with —I and/or —M effects lower the reaction rates (81ZN(B)609). 

Polycyclic phenols. Polycyclic aromatic ketones such as 1 can be converted into phenols by dehydrogenation of the corresponding enol acetates with o-chloranil... 

Doping with o-chloranile (CA) or kxline (J). Index indicates molar ratio CA, J/N -chelate... 

Sessler and coworkers have also developed a 3 -I- 2 approach to meso-diarylsapphyrins. This strategy, which is based on those used by Ogoshi and Smith ° to generate mc50-arylporphyrins, is outlined in Scheme 5.2.5. It involves the acid-catalyzed condensation of the diol 5.48 with the diacid tripyrrane 5.14. After oxidation with o-chloranil and chromatographic workup, diphenylsapphyrin 5.49 was obtained in ca. 3% yield. While less direct than the one-pot approach to 10,15-diarylsapphyrins outlined earlier (Schemes 5.1.6 and 5.1.7), this strategy allows synthetic access to isomeric 5,20-substituted diarylsapphyrins (e.g., 5.49). 

Sulfacetamide in ophthalmic solutions can be determined by its reaction with phenothiazine and N-bromosuccinimide at pH 6 to yield a blue product which absorbs at 605 nm. The recoveries are 96.7-100.7% (62). Sulfacetamide has been determined by its reaction with o-chloranil at pH 9 to yield a purple product with absorption maximum at 525 nm. Beer s law is obeyed over the concentration range 10 to 70 pg/ml of sulfacetamide sodium (63). 

By using 10mol% of benzoylquinidine (BQD, la), a variety of acid chlorides reacted efficiently with o-chloranil at — 78 °C in the presence of nonnucleophilic Hiinig base (iPr2EtN, DIPEA) (Scheme 10.2). The desired lactones 2 were produced in up to 91% yield with excellent enantiopurity. On the other hand, o-bromanil and 9,10-phenanthrene quinone were also successfully applied in this cycloaddition reaction. 

Benz[a]acridine is reduced by lithium in liquid ammonia to the 1,4,7,12-tetrahydro derivative, m.p. 177°C (M, Schaefer Ridder and U. Engelhardt, J. org. Chem.. 1981, 46, 2895). Oxidation with o-chloranil gives 1,4-... 

A [4 + 2] reaction has been postulated as an explanation for the reaction of the mesoionic 1,3-dithiolylium-4-ones (124) via their nondetectable tautomeric ketene (133) with o-chloranil (134) to afford (135) (Scheme 30) <81ZN(B)609>. 

Thiobenzylation. Benzyl sulfides are dehydrogenated to give benzalsulfonium salts on heating with o-chloranil at 80°. These can be used to react with p-keto esters. If a larger excess of o-chloranil is present (3 equiv.) the initial products are converted into the benzyhdene derivatives. ... 

Thietes (thiacyclobutenes) (190) give substituted 2,3-dihydro-1,4-benzodioxins (191), when treated in dichloromethane at reflux with o-chloranil or o-bromanil <87H(26)969>. 

Fig. 10. Intensity dependence of the steady-state photocurrent and photoinduced electron spin resonance in violanthrene treated with o-chloranil.

Fig. 11. Semilog plots of the time dependence of photoconductivity and light induced in ESR in violanthrene treated with o-chloranil.

Thus the band at 7000 A (in Fig. 12a) would be the violanthrene positive ion radicals in the solid matrix. A charge transfer band of violanthrene and any of the added acceptors would not be the same point for each acceptor molecule, and with o-chloranil it would be expected out in the infrared, from all the other indications and it is not there. What there is, then, is a complete transfer, not a charge transfer complex at all, but a complete transfer from the donor to the acceptor... 

Fig. 12. (a) Curve A—solid state absorption spectrum of pure violanthrene Curve B—difference between solid state absorption spectrum of violanthrene treated with BF3 and that of pure violanthrene Curve C—difference between solid state absorption spectrum of violanthrene treated with o-chloranil and that of pure violanthrene Curve D— difference between solid state absorption spectrum of violanthrene treated with iodine and that of pure violanthrene. Part B (b) Absorption spectrum of violanthrene dissolved in concentrated sulfuric acid for one hour. 

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