L,2-Dimethoxy-4-nitrobenzene

For the anode process at comparable conditions, the yield of l,2-dimethoxy-2-nitrobenzene depends distinctly on the electrical natnre of a micelle. Namely, the yields are equal to 30, 40, and 70% for the positively, negatively, and nentrally charged micelles, respectively. The observed micellar effect corroborates the mechanism that inclndes 1,4-dimethoxybenzene cation-radical and nitrogen dioxide radical as reacting species. 

V in both methanol and acetonitrile. These values, combined with the doping density and the band gap of 1.12 eV for p-Si places the conduction band edge in methanol and acetonitrile at -0.85V (vs SCE). The supraband edqe redox couples chosen for the two electrolytes were 1,3 dimethoxy-4-nitrobenzene (8,=-l -0V vs SCE)for methanol, and 1 nitronaphthalene (E0=-l. 08), 1, 2 dichloro 4-nitrobenzene (E0= -0.95), and anthraquinone (Eo=-0.95) for acetonitrile. These redox couples lie from 0.IV to 0.24V above the conduction band edge of p-Si, and hence, in the conventional model, could not be photoreduced by p-Si. 

The pH dependence of the regioselectivity for the nucleophilic photosubstitution of 3,4-dimethoxy-l-nitrobenzene by n-butylamine gives21 2-methoxy-5-nitro-Af-butylaniline as the major product at pH = 11 (equation 19). At pH = 12, the ratio of the major product to 2-methoxy-4-nitro-7V-butylaniline increases to 12 1 the increased selectivity is caused by hydroxide ion, which can either promote exciplex formation or act as a base catalyst in deprotonation steps following the cr-complex formation22. 

Hiller and coworkers reported an NMR and LC-MS study on the structure and stability of l-iodosyl-4-methoxybenzene and 1-iodosyl-4-nitrobenzene in methanol solution [195]. Interestingly, LC-MS analyzes provided evidence that unlike the parent iodosylbenzene, which has a polymeric structure (Section 2.1.4), the 4-substituted iodosylarenes exist in the monomeric form. Both iodosylarenes are soluble in methanol and provide acceptable and NMR spectra however, gradual oxidation of the solvent was observed after several hours. Unlike iodosylbenzene, the two compounds did not react with methanol to give the dimethoxy derivative ArI(OMe)2 [195]. 

A suspension of 20.1 g 1,5-dimethoxy-2,4-dinitrobenzene (90.0 mmol) in 117 mL water was stirred under reflux and treated dropwise over 30 min with a solution of sodium polysulfide, prepared by heating 28.6 g Na2S-9H20 (119 mmol) and 6.8 g sulfur (213 mmol) in 120 mL water. The reaction mixture was stirred under reflux for a further 3 h and then cooled and evaporated under reduced pressure at 45°C to give a dark residue. This was extracted several times with warm EtOAc, and the combined extracts were filtered through a short column of silica gel. The eluates were washed with water and evaporated to dryness. The residue was dissolved in 1 N HCl, filtered, and basified with aqueous NaOH to give 11.0 g l-amino-2,4-dimethoxy-5-nitrobenzene, in a yield of 63%, m.p. 126-128°C. 

A mixture of 6.0 g l-amino-2,4-dimethoxy-5-nitrobenzene (30.9 mmol), 20.0 g diphenyliodonium-2-carboxylate (61.4 mmol), and 0.4 g copper(II) acetate (2.2 mmol) in 180 mL dry DMF was stirred at 90°C (bath temperature) for 7 h and then at 20°C for overnight. Most of the DMF was evaporated under reduced pressure, and the residue was taken up into CH2CI2, washed twice with water, and extracted into 0.5 N KOH. The alkaline layer was back extracted with CH2CI2 and filtered, and the filtrate was acidified at 0°C to give 9.7 g 2-r(2,4-dimethoxy-5-nitrophenyl)amino]-benzoic acid, in a yield of 99%, m.p. (CHCls/MeOH) 283-285°C. 

Dihydro-5,8-dihydroxy-6,6 -dimethoxy-4 -methylnaphthaIene-2-spiro-2 -2 /7-benzofuran-l,3, 4-trione in nitrobenzene heated at 200° for 2 h->- 6,ll-dihydroxy-3,8-dimethoxy-l-methylbenzo[Z ]xanthene-7,10,12-trione. Y 74%. F.e.s. C.B. de Koning et al., J. Chem. Soc. Perkin Trans. I 1988, 3209-16. 

An attempt to combine electrochemical and micellar-catalytic methods is interesting from the point of view of the mechanism of anode nitration of 1,4-dimethoxybenzene with sodium nitrite (Laurent et al. 1984). The reaction was performed in a mixture of water with in 2% surface-active compounds of cationic, anionic, or neutral nature. It was established that 2,5-dimethoxy-l-nitrobenzene—the product—was formed only in the region of potentials corresponding to simultaneous electro-oxidation of the substrate to the cation radical and of the nitrite ion to the nitrogen dioxide radical (1.5 V versus saturated calomel electrode). 

A shikimate-chorismate biogenesis can be more confidently predicted for 6-nitro-wo-vanillic acid (243), a constituent of an as yet unidentified Australian toadstool belonging to Cortinarius 280), The compound (243), the only example of a nitroaromatic metabolite from Cortinarius, produces an intensely yellow dianion [UV/vis. (ethanol-h alkali) max(l g ) = 270.5 (4.53), 429 nm (4.76)] which is responsible for the bright yellow colour of the cut flesh of this fungus. A yellow nitro compound, 3,5,6-trichloro-l, 4-dimethoxy-2-nitrobenzene, has been isolated from Phellinus rimosus = Pomes robiniae) 147). 

---