Tetrachloro-p-benzoquinone

One of the primary starting materials for all members of this group is chloranil (tetrachloro-p-benzoquinone). Today, it is customarily prepared by oxidative chlorination of hydroquinone. 

An excess of tetrachloro-p-benzoquinone (chloranil) in o-dichlorobenzene is added to 2 moles of 3-amino-N-ethylcarbazol and dry sodium acetate, which acts as an acid trap. The mixture is stirred for 6 hours at 60°C, then within 5 hours heated to 115°C under vacuum, after which benzenesulfochloride is added at the same temperature. Cyclization is achieved by increasing the temperature to 175-180°C. The reaction mixture is agitated until no more acetic acid appears in the distillation receiver (for 4 to 8 hours). The reaction product is vacuum filtered, residual o-dichlorobenzene removed by steam distillation, the product washed, and dried. A patent which was issued in 1980 claims a much improved yield if the reaction is performed in the presence of only a slight excess of chloranil, provided 0.15 to 1.8 wt% water is added to the reaction mixture [5],... 

Megestrol Megestrol, 17a-hydroxy-6a-methylpregna-4,6-dien-3,20-dione acetate (28.3.9), is a product of dehydrogenation medroxyprogesterone (28.3.7) with chloranil (tetrachloro-p-benzoquinone) in the presence of p-toluenesulfonic acid, which results in the formation of an additional double bond at position Cg-Cy, and subsequent acetylation of the product (28.3.8) leads to the desired megestrol (28.3.9) by acetic anhydride in the presence of p-toluenesulfonic acid [78,79],... 

Triphenyl-X -phosphorin interacts with iodine or other polarizable electron donors, as well as with such electron acceptors as tetrachloro-p-benzoquinone and tetracyanoethylene, to produce deeply colored solutions. Such coloration points to the formation of charge-transfer complexes (see p. 43). In some cases electron transfer occurs with the formation of 2.4.6-triphenyl-X -phosphorin cation radical and tetracyanoethylene anion radical. Weber is currently investigating the details of these reactions (see p. 43). 

Stade observed an interesting oxidation with tetrachloro-p-benzoquinone. In methylene chloride an intense red coloration appears, but no signal in the ESR spectrum. Apparently only a charge-transfer complex 61 is formed, without electron transfer. A similar observation has been made in the reaction of N, N, N, N -tetramethyl-p-phenylenediamine with tetrachloro-p-benzoquinone in non-polar solvents Here, as in our case, electron transfer does not take place until a polar solvent such as acetonitrile is added. The ESR spectrum initially shows the doublet of 55 (23,2 Gauss) overlapping with the sharp sin et of tetrachloro-semi-quinone 62 (which has a somewhat smaller g factor). The semiquinone signal slowly disappears until finally only the doublet of 58 remains. The following scheme summarizes the reaction course ... 

A system has been proposed which involves quinone/hydroquinone interconversions. A number of such couples are insoluble in acid solution and can therefore be used as active solid masses when made conductive by the addition of graphite. A system which has been studied experimentally is based on anthraquinone, Q, and tetrachloro-p-benzoquinone (chloranil), Qr, and their reduced or hydroforms. The overall cell reactions are then... 

Inverted porphyrin or 2-aza-21-carbaporphyrin 88 also known as an NCP (Figure 3) was first isolated as a by-product of normal acid-catalyzed condensation of pyrrole and benzaldehyde (1994ACI779, 1994JA767). Latos-Grazynski and coworkers employed a Rothemund reaction between tolualdehyde and pyrrole in the presence of BF3-Et20 in DCM, followed by oxidation with 2,3,5,6-tetrachloro-p-benzoquinone (chloranil) to obtain NCP (1994ACI779). Simultaneously, Furuta and coworkers also reported... 

Diorgano telluriums form donor-acceptor complexes with 1,4-dinitrobenzene, tetrachloro-p-benzoquinone, and 7,7,8,8-tetracyano-p-quinodimethane. These adducts are formed when the components are refluxed in acetonitrile or acetone. The following adducts were prepared ... 

Another route to Pd(0) complexes reported recently is by reaction of [Pd(CNPh)2] with activated monoolefins 18, 220). With fumaronitrile maleic anhydride and p-quinones, 1 1 adducts are formed, whereas, with tetrachloro-p-benzoquinone, an adduct is formed in which the Pd-to-ligand ratio is 2 1. Another new procedure is the use of bis-(dibenzlideneacetone) palladium(O) which reacts directly with olefins 145). 

The details of the electron-transfer processes involved on irradiation of mixtures of tetrachloro-p-benzoquinone with the cyclopropane derivatives (58) and (59) have been reported. The intermolecular electron-transfer processes lead to the formation of the radical cation of the cyclopropanes. Ring-opening of the cyclopropanes results from these species. ... 

By careful choice of conditions, the simplest dipyrromethane, bis(pyrrol-2-yl)methane, can be obtained directly from pyrrole with aqueous formalin in acetic acid reaction in the presence of potassium carbonate allows 2,5-bis-hydroxymethylpyrrole to be isolated. This diol reacts with pyrrole in dilute acid to give tripyrrane and from this, reaction with 2,5-bis(hydroxymethyl)pyrrole gives porphyrinogen, which can be oxidised with chloranil (2,3,5,6-tetrachloro-p-benzoquinone) to porphine, the simplest porphyrin. 

AI3-03797 1,4-Benzoquinone, 2,3,5,6-tetrachloro- p-Benzoquinone, 2,3,5,6-tetrxhloro- Caswell No. 171 CCRIS 7155 Chloranil p-Chloranil Chloranile Covetsan 2,5-Cyclohexadiene-... 

Very exciting results for the oxyfunctiona-lization of alkanes were also obtained using photoinduced SET reactions as the key step. [23] The principle applied here is that after electron tranfer oxidation of the alkane 18 the aciditiy of the C-H bonds of the resulting radical cation 20 is dramatically increased. Thus, deprotonation to the radical 23 occurs, which then can be trapped by oxygen. For example, if 1 is irradiated in an oxygen saturated acetonitrile solution in the presence of 1,2,4,5-tetracyanobenzene (TCB), 4 is obtained as the main product. Changing from TCB to 2,3,5,6-tetrachloro-p-benzoquinone (Chi) the radical 23 is further oxidized to the cation 26, which in turn can now also be trapped by acetonitrile leading to amidated products 24. 

Mixed donor ligands. The reaction of [Fe(salen)] with a range of quinones yields [(Fe(salen) 2(quin)] (quin = p-benzoquinone, tetramethyl-p-benzoquinone, and tetrachloro-p-benzoquinone) which probably contain quinone ligands. With 9,10-phenanthraquinone and 1,2-naphthaquinone, [Fe(salen)(quin)] is formed. The reactions of Fe(salen) with a variety of organic halides and nitro- and nitroso-compounds have been studied. With PhN02, [Fe (salen)20], and PhN(0)=NPh are formed whereas the PhNO reaction yields the same iron(iii) compound and PhN=NPh. Reaction with RNO (R = 2-biphenyl or... 

Figure 16. EPR spectrum obtained at room temperature of a DEAE-cotton of 2.58% N after its reaction with 2,3,5,6-tetrachloro-p-benzoquinone (o-chloranil) in chloroform. (g-va1ues = 2.0059.)...

The first tetra-TTF calix[4] pyrrole conjugate 170 has been synthesized by the condensation of acetone and the corresponding monopyrrolo-TTF unit. This calix[4]pyrrole in its 1,3-altemate conformation acted as a host for neutral electron-deficient guests such as 1,3,5-trinitrobenzene, tetrafluoro-p-benzoquinone, tetrachloro-p-benzoquinone and p-benzo-quinone. The addition of chloride ions served to effect release of these guests and thus neutral substrate recognition process could be blocked by the addition of chloride anion (2004JA16296). 

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