Chloranil hydrolysis

A recent example is the hydrolysis of chloranil with aqueous sodium hydroxide, which is a multistep process leading to the chloranilate dianion, Fig. 5.21 [26]. In a two-phase reaction system consisting of solid chloranil and aqueous sodium hydroxide, the rate-limiting step is the initial attack of hydroxide ion on chloranil. Hydrolysis rates at the 010, 100 and 001 cleavage planes of chloranil were separately measured [27], and different reactivities were found this was rationalised by considering the exposure of the initially reactive functionality (assumed to be the carbonyl group) at the surface, as shown in Fig. 5.22. Hydrolysis at the 010 and 100 planes was shown to be a surface reaction driven by the hydroxide concentration adjacent to the interface the 001 plane was shown to react more slowly by prior dissolution of chloranil before reaction. 

A simple synthesis of tetrahydroxyben2oquinone by methoxylation—hydrolysis of chloranil has been reported (265). Similarly, tetraar5ioxyben2oquinones have been prepared from chloranil and alkali salts of phenols (266). 

Tile same methodology as mentioned for the preparation of (9) was applied for the synthesis of 8-nitro-l,6-naphthyridines. Heating diethyl N- 3-nitropyridin-4-yl)aminomethylenemalonate (12) in diphenyl ether yields ethyl 8-nitro-l,6-naphthyridin-4(lH)-one 3-carboxylate (13) (63JCS4237, 30%) and acid treatment of 4-( y, y-diethoxypropylamino)-5-nitro-2-(/3,/3 -trifluoroethoxy)-pyridine (14) gives in a similar way 8-nitro-5-(/3, /3-triflu-oroethoxy)-l,2-dihydro-l,6-naphthyridine (15, 76%). Subsequent oxidation with chloranil, acid hydrolysis, and methylation with methyl iodide gives 8-nitro-6-methyl-l,6-naphthyridin-5(6H)-one (16,63%) (81JHC941). 

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... 

NMR spectrum showing the presence of a 3-substituted pyridine with four nonequivalent methylene units in the substituent, and by its conversion to 2,3-bi-pyridyl with chloranil (26). Its synthesis was made by condensation of A -ben-zoylpiperidone (258) with ethyl nicotinate (259) followed by heating with concentrated hydrochloric acid, resulting in hydrolysis, decarboxylation, and ring closure (Scheme 18) 401). Application of the Mundy A-acyllactam rearrangement to A-nicotinoylpiperidone (261) has also led to a synthesis of anaba-seine (8) (Scheme 18) 402). 

Another very instructive case concerns the alleged initiation of a cationic polymerisation by a charge-transfer complex formed by the compound chloranil (2,3,5,6-tetrachloroquinone) with the monomer N-vinyl-carb-azole. It was shown (Natsuume et al., 1969 1970) that this compound is not an initiator, but that the polymerisations were caused by a hydrolysis product, 2-hydroxy-3,5,6-trichloroquinone, which is a strong acid. One has learnt from this finding to be extremely suspicious of any claims for charge-transfer catalysis and to test one s suspicions by appropriate experiments involving progressive purification of the putative catalyst. 

Pentachlorophenol produces a wide variety of transformation products including chloranilic acid (2,5-dichloro-3,6-dihydroxy-benzo-l,4-quinone) by hydrolysis and oxidation, a dichlorocyclo-pentanedione by ring contraction, and dichloromaleic acid by cleavage of the aromatic ring (Figure 4.4) (Wong and Crosby 1981). 

To cite another of the many possible examples, tetrachloro-p-quinone (chloranil) is transformed under similar conditions to give the hexachloro-p-diketone derivative (III). Hydrolysis of this para derivative with caustic soda caused the ring to break with formation of dichlormaleic acid, trichloroethylene, and sodium chloride as follows ... 

The base-catalyzed cyclization of ethyl 3-[alkyl(4-cyanopyridazin-3-yl)amino]propanoates gives ethyl 8-alkyl-5-amino-7,8-dihydropyridazine-6-carboxylates 1, which by acidic hydrolysis were converted to the corresponding ends 2. Due to their air sensitivity, ends 2 are partly converted into ethyl 8-alkyl-5-oxo-5,8-dihydiopyiido[2,3-c]pyridazine-6-carboxylates 3. To avoid mixtures, the oxidation is completed by treatment with tetrachloro-l,2-benzoquinone (o-chloranil).20... 

Chloranil (42), 2,3,5,6-tetrachloro-l,4-benzoquinone, is prepared either by the oxidative chlorination of 2,4,6-trichlorophenol or by the oxidative hydrolysis of pentachlorophenol. 

It is used mainly for seed treatment against smut and diseases of vegetable seeds (Schoene et al., 1949). Its use as a foliage fungicide is limited because it decomposes partly by hydrolysis and partly photochemically (Burchfield and McNew, 1950), and sublimates in hot weather. Neither can it be used efficiently as a soil fungicide, because it also rapidly decomposes in the soil (Domsch, 1958). One of its degradation products is chloroanilic acid (21), 2,5-dichloro-3,6-dihydroxy-l,4-benzoquinone, which is also biologically inactive. The acute oral lDj chloranil for rats is 4000 mg/kg. 

As shown in Scheme 1, the synthesis of fert-butyl phenalenyl radical 10 started from 2,7-di-ferf-butylnaphthalene in ten steps. Bromination of 2,1-di-tert-butylnaphthalene gave 6 in high yield, which was converted into aldehyde by lithiation followed by reaction with DMF. Successive Reformatsky reaction afforded ester 7, which upon reduction, hydrolysis, and Friedel-Crafts acylation reaction gave the phenalanone 8. The key intermediate 9 was then obtained as pale yellow crystals by reduction of 8 and subsequent dehydration. Oxidation of 9 with p-chloranil in degassed toluene led to a blue neutral radical solution while similar treatment in hexane gave deep blue needles. This crystal showed high stability in the absence of air, while changing into phenalanone derivatives and other byproducts in 1 week in air. 

The proof of structure was obtained by the hydrolysis of 64 to the diacid 65 followed by simultaneous oxidation and decarboxylation of the latter with chloranil to 1,2,5-triphenylpyrrole 66. 

The bis-HCl salt is easily oxidized also, but can be handled. The tetrafunctional monomer for PBO is prepared from resorcinol diacetate by nitration and hydrogenation. Care must be taken in view of explosive side products. A detailed description appeared recently. A probably more economical synthesis of 4,6-diaminoresorcinol has become available by nitration of 1,2,3-trichlorobenzene followed by alkaline hydrolysis and hydrogenation. The status of the work aimed at a commercial process for cis-PBO was reviewed recently.Diaminohydroquinone, the precursor for trans-PBO, can be prepared from chloranil by ammonolysis followed by hydrogenation ... 

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