5-Acetoxy-1-hydroxy-4-nitro

Amino-4-ethynylpheno1. A mixture of 4-hydroxy-3-nitro-acetophenone(6) (50.Og, 0.28 mole) and acetic anhydride (100.Og, 0.98 mole) was stirred at reflux for 45 minutes to form a clear, light yellow solution. The excess acetic anhydride was stripped off under reduced pressure to give an oil which gradually solidified. Recrystallization from 500 ml of isopropanol (charcoal) yielded 43.Og (63%) of light yellow crystals of 4-acetoxy-3-nitro-acetophenone, mp 62-63°C. 

Acetoxy-5-hydroxy- 549 4-Acetoxymercuro- 628 4-(a-Acetoxy-2-nitro-benzyl)-l-acetyl-3,5-dimethyl- 539... 

The first in this series to be reported was 4-oxoisoxazoline-3,5-dicarboxylic acid diethyl ester, which was formed by the reaction of nitrous acid on diethyl acetonedicarboxylate in 1891. Quilico described a number of syntheses in his 1962 review and the most general include the reaction of hydroxylamine and a-hydroxy-(or acetoxy)- 3-diketones and the conversion of 4-isoxazolediazonium salts to the hydroxy moiety (62HC(17)1, p. 3). Additional syntheses reported were the oxygenation of a 4-boric acid derivative (67JOM(9)l9) and peroxide oxidation of a 4-nitro-2-isoxazoline (Scheme 151) (79ZOR2436). 

Wahrend 5a-Chlor-6/3-nitro-3/3-acetoxy-cholestan mit waBr. Chrom(II)-chlorid eben-falls das 5a-Hydroxy-3 >-acetoxy-6-hydroximino-cholestan liefert3,... 

The reactions of the homocyclic ring of benzofuroxans, which are described in detail in Section 4.22.3.3, provide access to numerous derivatives. Nucleophilic displacement of halides is facile when activating nitro groups are present, allowing alkoxy, aryloxy, thio and amino groups to be introduced. Electrophilic substitutions, e.g. nitration, are also valuable. Further transformations may also be performed on benzo-ring substituents. Such modifications include acetoxy to hydroxy acetamido to amino and acyl halides to esters and amides. Some reactions of the substituents of monocyclic furoxans allow hetero-substituted analogues of benzofuroxans to be prepared. For example, pyridazinofuroxans are formed by condensation of diacylfuroxans with hydrazine. 

Ethan 2-Acetamino-2-hydroxy-l-oxo-1-phenyl- E14a/2, 68 (R-CHO/R-CO-NH2), 215 (R-CHO/Amin) Furo 2,3-b[pyridin 3-Acetoxy-3-methyl-2,3-dihydro- E6b/1, 117 (OH -+ O-CO-CH3) Hydroxylamln N-[4-(rra s-2-Methoxycarbonyl-ethenyl)-phenyl]- E16a, 58 (Nitro-Red.) Malonsanre Methyl- -anilid E5. 

Hydroxy-9-(l-acetoxy-athoxy)- 967 10-Hydroxy-9-benzyl- 966 10-Hydroxy-9-(4-tert.-butyl-benzyl)- 966 10-IIydroxv-9-(l,4-dioxanyl)- 967 10-Hydroxy-9-(4-methoxy-benzyl - 966 10-Hydroxy-9-(4-methyl-benzyl)- 966 10-Hydroxy-9-(4-nitro-benzyl)- 966 10-IIydroxy-9-(phenoxy-methoxy - 967 10-Hydroxy-9-(l-propanoyloxy-athoxy)- 967 10-Hydroxy-9-[tetrahydrofuryl-(2)-oxy]- 967... 

Dioxo-4-methyl- 1148 3/3-IIydroxy-6/3-nitro- 1331 3/3-Hydroxy-6-oxo- 1331 6/3-Nitro-3/ -acetoxy- 1330 3-Oxo- 1470,1478 6-Oxo-3-hydroximino- 1331... 

Figure 6 Rf values of 2- ubstituted benzoic acids in different solvents. The solvent composition organic componentAvater (40 60 v/v) with addition of 0.1 M tetramethyl ammonium bromide (pK value in parentheses) O, tenzoic acid (4,19) , 2-hydroxy (2,97) , 2-acetoxy (3.5) , 2-carboxy (2.91/5.59) , 2-nitro (2.16) , 2-methyl (3.91) A, 2-amino (6.97) T, 2-chloro (2.92). (From Ref. 162, by permission of Friedr. Viewig and Sohn.)...

The nitro group in quaternary salts of 4-nitropyridine is easily replaced. Recrystallization of the methiodide from undried acetone gives l-methyl-4-pyridone . Reaction of 4-nitropyridine with benzyl chloride yields 1-benzyl-4-pyridone, and with benzyl bromide, l-benzyl-3,5-dibromo-4-pyridone (nuclear bromination is thought to result from the oxidation of hydrobromic acid by nitrous acid) the experimental description suggests that in these reactions nucleophilic replacement of nitro by halide may occur initially . The consequences of the autoquaternization of 4-nitropyridine have already been mentioned. The formation of 4-hydroxypyridine from 4-nitropyridine and acetic anhydride a presumably involves the acetyl-pyridinium salt. 4-Nitropyridine 1-oxides give with acetic anhydride mainly 4-hydroxy-or 4-acetoxy-3-nitropyridine l-oxides sic but the presence... 

The solvent effect on the aromatization of the cis- and /rans-isomers of 4-nitro-3,4,5-trimethylcyclohexa-2,5-dienyl acetate (43) (prepared from acetyl nitrate and 1,2,3-trimethylbenzene) has been reported and two major pathways of solvolytic aromatization have been identified. In 50% H2SO4, loss of acetate yields the ipso-ion (44), which is then partitioned along two paths, one leading to oxidation (to 5-hydroxy-l,2,3-trimethylbenzene), the other to migration of the NO2 group, eventually giving 4-nitro-l,2,3-trimethylbenzene. Aromatization in weakly acidic systems leads to loss of nitrite ion, formation of ion (45), and subsequent proton loss to yield 5-acetoxy-l,2,3-trimethylbenzene. ° ... 

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