Catechol 4-nitro

A 4-nitro-l, 2-methylenedioxybenzene has been cleaved to a catechol with 2 N NaOH, 90°, 30 min a similar compound substituted with a 4-nitro or 4-formyl group has been cleaved by NaOCH3/DMSO, 150°, 2.5 min (13-74% catechol, 6-60% recovered starting material). ... 

Irradiation of an aqueous solution at 296 nm and pH values from 8 to 13 yielded different products. Photolysis at a pH nearly equal to the dissociation constant (undissociated form) yielded pyrocatechol. At an elevated pH, 2-chlorophenol is almost completely ionized photolysis yielded cyclopentadienic acid (Boule et al., 1982). Irradiation of an aqueous solution at 296 nm containing hydrogen peroxide converted 2-chlorophenol to catechol and 2-chlorohydroquinone (Moza et al, 1988). In the dark, nitric oxide (10 vol %) reacted with 2-chlorophenol forming 4-nitro-2-chlorophenol and 6-nitro-2-chlorophenol at yields of 36 and 30%, respectively (Kanno and Nojima, 1979). 

Some biologically important o-quinones can react with the superoxide ion giving catechol derivatives, which may play a role in many diseases. For example, compounds bearing a nitro-catechol moiety have been claimed to be efficient catechol-0-methyl transferase inhibitors (Suzuki et al. 1992, Perez et al. 1992). The transferase is the first enzyme in the metabolism of catecholamine a hyperactivity of this enzyme leads to Parkinson s disease. Therefore, prediction of biological activity and antioxidant properties of quinones is an important challenge for researchers. 

The pH values of efficient extraction correspond to the pH range where the molecular form of the respective phenol dominates. The recovery of 4-nitro-phenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 4-chlorophenol, 1-naphthol, and 2-naphthol is above 90% (the ratio of aqueous organic phase volume is 3 1). The extraction of naphthol and 4-chlorophenol is significant even at pH > pffa, more than 40 and 24% at pH > 10, respectively. Recovery of picric acid (2,4,6-trinitrophenol) is about 90% at pH 1.5-12.0, where the anionic form of picric acid dominates. Obviously, the high extraction is caused by high hydrophobicity of picrate anions. Recovery of the phenol itself and diatomic phenols, catechol and resorcinol is rather moderate (79,58, and 20%, respectively pH 1-7), which could be explained by relatively high hydrophi-licity of these compounds. 

The above process is applicable to almost all hydroxyalde-hydes in which the hydroxyl and carbonyl groups occupy ortho or para positions relatively to each other 1 in the latter case derivatives of hydroquinone are produced. When the hydroxyl and carbonyl groups occupy the meta position with respect to each other, no reaction takes place, as is also the case with certain ortho and para compounds containing nitro groups and iodine atoms. o-Hydroxyacctophenone and -hydroxyaceto-phenone are also capable of yielding catechol and hydroquinone respectively under the above conditions. 

N 21-54% orn-colored ndls + % H2O (from dil ale), mp - explodes violently at 169-72° readily sol in glacial acet ac, chlf 8c ethyl acet sol in warm alkalies, giving a blue-red soln si sol in acet 8c benz was prepd by diazotizing either 5-nitro-3-amino be nzopyro-catechol-l-methyl ether or 2-bromo-5-nitro-3-aminoanisole (Refs 1, 2 Sc 3)... 

Groups of 10-20 male Fischer 344 rats, seven weeks of age, received catechol (> 99.8% pure) in the diet at concentrations of 0 or 1.5% for four weeks followed by 0.8% for 47 weeks either with no other exposure or one week after exposure to A-mcthyl-A"-nitro-A -nitrosoguanidinc to initiate stomach carcinogenesis. With catechol alone, the incidence of forestomach papillomas was 1/15 compared with 0/10 in untreated controls. Glandular stomach adenocarcinomas were found in 3/15 rats compared with 0/10 in controls. Catechol increased the incidence of squamous-cell carcinomas of the forestomach induced by the initiator from 5/19 to 19/19 (p < 0.001). In the glandular stomach, the incidence of adenocarcinomas in the pyloric region was 18/19 (p < 0.001) compared with none in rats given only the initiator (Hirose et al., 1987). 

Apart from nitrophenols, 4-nitrocatechol and nitrobenzoquinone have also been detected as nitro derivatives [54,79,100]. They are secondary photoproducts and are thought to originate from the nitration of catechol and hydroquinone, in the latter case followed by the oxidation of nitrohy-droquinone [54,100]. 4-Nitrocatechol might in principle derive from catechol nitration or from 4-nitrophenol hydroxylation. However, the conversion of 4-nitrophenol into 4-nitrocatechol upon nitrate photolysis is rather limited [109] and cannot account for the observed time evolution starting from phenol [54]. 

Absence of nitro derivatives was also observed upon irradiation of nitro-phenols and nitrate. Also in this case, the electron-withdrawing character of the nitro group can account for the inhibition of nitration [109]. The difficulty to nitrate nitrophenols to dinitrophenols is widely recognised [125] and also constitutes a problem in environmental chemistry, since field data seem, in contrast, to indicate that the nitration of 2-nitrophenol to 2,4-dinitrophenol in the atmospheric aqueous phase (e.g. cloud water) is an important process [126]. In fact, aqueous-phase nitration might be a relevant sink for 2-nitrophenol and possibly the main source of the dinitro compound, which is a powerful phytotoxic agent [127,128]. In the presence of nitrate under irradiation the main transformation intermediates of nitrophenols are the hydroxyl derivatives, while other compounds may derive from the direct photolysis of the substrates (catechol and 2-nitrosophenol from 2-nitrophenol hydroquinone, benzoquinone, hydroxybenzoquinone and 4-nitrosophenol from 4-nitrophenol) [109]. 

Catechols and hydroquinones can be converted (91-98%) into quinones by cerium(IV) salts coated onto silica as free-flowing yellow powder from impregnation with cerium(IV) ammonium nitrate. This reaction is usually performed in the presence of magnesium sulfate. The same (NH4)2Ce(N03)6 SiQ2 reagent in the dry state effects oxidative nitrations of arenes. For example a-mq>hthol is converted to the Orth) (42%) and the para (38%) nitro compounds, while its metiiyl or ethyl ethers give exclusively the para nitration product (equation 4). In solution, the products are cmtaminated with the products of dinitration and of oxidation into quinones. ... 

Fig. S. A and B. Visible spectra of (A) 4-nitrocatechol at pH 8.S and the pyrocatechase-4-nitro-catechol complex (50 mM Tris-acetate pH 8) (B) 4-nitrocatechol at pH 13 and the protocatechuate 3,4-dioxygenase-4-nitrocatechol complex (50 mM Tris-acetate pH 8)...

The reaction of peroxynitrite (ONOO ) was also investigated with a series of para-substituted phenols in phosphate buffer solutions . The corresponding 2-nitro derivative and the 4-substituted catechol were the major products. The reaction exhibits good correlation with Hammett ap+ and half-wave reduction potentials, suggesting a... 

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