O -nitro

If phenol is treated even with dilute nitric acid at room temperature, nitration readily occurs with the simultaneous formation of the yellow o-nitro-phenol and the white /> nitrophenol. These compounds can be readily... 

Coloured salts loith alkalis. Dissolve a few crystals of o-nitro-phenol in a few ml. of 10% NaOH solution. An orange-coloured solution is produced, and becomes almost colourless on the addition of acids. Alkali restores the orange coloration, and so the solution exhibits the properties of an indicator. 

Nitrations in acetic anhydride, or in solutions containing benzoyl nitrate ( 5.2) or dinitrogen pentoxide ( 4.2.3) have long been associated with the formation from some aromatics of higher proportions of o-nitro-compounds than are formed under other conditions. 

Trifluoromethyl)benzene o Nitro(tnfluoro rn Nitro(tnfluoro p Nitro(tnfluoro... 

Table 19 3 lists the ionization constants of some substituted benzoic acids The largest effects are observed when strongly electron withdrawing substituents are ortho to the carboxyl group An o nitro substituent for example increases the acidity of benzoic acid 100 fold Substituent effects are small at positions meta and para to the carboxyl group In those cases the values are clustered m the range 3 5-4 5... 

Three selective methods to remove protective groups are receiving much attention assisted, electrolytic, and photolytic removal. Four examples illustrate assisted removal of a protective group. A stable allyl group can be converted to a labile vinyl ether group (eq. 4) a /3-haloethoxy (eq. 5) or a /3-silylethoxy (eq. 6) derivative is cleaved by attack at the /3-substituent and a stable o-nitro-phenyl derivative can be reduced to the o-amino compound, which undergoes cleavage by nucleophilic displacement (eq. 7) ° ... 

A nitro group in the artho or para position to fluonne is known to enhance its replacement by hydroxyl [II, 12] Bromine and iodine are much less prone to hydrolysis under similar conditions The effect is much less pronounced with the meta nitro derivative (equation 11) With o-nitro-p-fluoroaniline, it is the amino group ortho to the nitro group, rather than meia fluorine, that is replaced by hydroxyl (equation 12)... 

General Conditions for each step and selectivity of m-substituted anilines As previously mentioned, Hauser and Reynolds reported on factors governing the first step of the Conrad-Limpach reaction but they tvere by no means exhaustive. Other than the conditions reported above for the first step, HClAleOH, CHCI3 or CHCI2 (neat or with acid catalyst), PhMe or PhH with removal of water with or without acid catalyst, or EtOH/AcOH/CaS04 were reported to provide the desired enamino-ester from an aryl amine and 3-keto-ester. Hauser and Reynolds also noted that o-nitroaniline and o-nitro-p-methoxyaniline failed to form the desired enamino-ester under conditions which they reported. 

Radicaloid substitution has not been extensively studied in the thiophene series. Molecular orbital calculations indicate that substitution should occur in the a-position. This has been found to be the case in the Gomberg-Bachmann coupling of diazohydroxides with thiophenes which has been used for the preparation of 2-(o-nitro-phenyl) thiophene, 2-(p-toluyl) thiophene, " " and 2-(p-chloro-phenyl)thiophene. " Coupling in the /8-position has been used for the preparation of 1,3-dimethyl-4,5-benzisothionaphthene (148) from 2-amino-tt-(2,5-dimethyl-3-thienyl)cinnamic acid (149). A recent investigation describes the homolytic phenylation of 2- and 3-phenyl-... 

Perhaps the most reliable method for the reductive cyclization of a nitro ester to a hydroxamic acid is that which involves treatment with sodium horohydride in the presence of palladium on charcoal. Although under these conditions aromatic nitro compounds are reduced to amines, o-nitro esters such as 53, in which the ester group is suitably oriented with respect to the nitro group, give good yields of cyclic hydroxamic acids (54). Coutts and his co-... 

A novel synthesis of 2-aminoquinoxalin-3-one 1-oxide has been effected by the hydrogenation of o-nitro-l-cyanoformanilide in ethanol in the presence of Adam s catalyst.- ... 

Benzaldehyde, o nitro, 46,81 Benzaldehyde, 2,4,6-trimethyl-, 47,1 Benzaldehydes, halogen- and methyl-substituted, preparation from diazomum salts and formal doxime, 46, IS... 

N-(p-Dimetliylaminophenyl)-Qr-(o-nitro-phenyl)nitrone from reaction of o-nitrobenzylpyridinium bromide and -nitrosodimethylaniline, 46, 82... 

Di-o-nitrophenyl disulfide was first prepared by the action of hydriodic acid on o-nitrobenzene sulfochloride.1 It has also been prepared by the reduction of o-nitrobenzene sulfinic acid with hydrogen bromide 2 by the reduction of ethyl-o-nitro-phenylsulfonacetate with ammonium sulfide 3 and by the deamination of 4,4,-diamino-2,2 -dinitrodiphenyldisulfide.4 The procedure given is the method of Blanksma5 as elaborated by Wohlfahrt.6... 

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