5-Nitroindole

Indole can be nitrated with benzoyl nitrate at low temperatures to give 3-nitroindole. More vigorous conditions can be used for the nitration of 2-methylindole because of its resistance to acid-catalyzed polymerization. In nitric acid alone it is converted into the 3-nitro derivative, but in a mixture of concentrated nitric and sulfuric acids 2-methyl-5-nitroindole (47) is formed. In sulfuric acid, 2-methylindole is completely protonated. Thus it is probable that it is the conjugate acid which is undergoing nitration. 3,3-Dialkyl-3H-indolium salts similarly nitrate at the 5-position. The para directing ability of the immonium group in a benzenoid context is illustrated by the para nitration of the conjugate acid of benzylideneaniline (48). 

Nitroindole [6146-52-7] M 162,1, m 141-142 , pK -7,4 (aq H2SO4). Decolorised (charcoal) and recrystd twice from aqueous EtOH. 

Nitroindole (ARf 40—45), 5-chloroindole (jiRf 60 — 65) and indole QiRf 70—75) yielded orange-yellow chromatogram zones on a pale yellow background. If the chromatogram was exposed to ammonia vapor for 15 s the color was intensified. The detection limits were 10 ng substance per chromatogram zone. 

Fig. 1 Reflectance scan of a chromatogram track with 80 ng substance per chromatogram zone 5-nitroindole (1), 5-chloroindole (2) and indole (3).

The values of the 1-hydroxy moiety of (5)-(- -)-iVb-acetyl- 1-hydroxytrypto-phan methyl ester (32), methyl l-hydroxyindole-3-butylate (33), iVb-methoxy-carbonyl-l-hydroxytryptamine (34), 1-hydroxymelatonm (19), l-hydroxy-6-nitroindole (35), and l-hydroxy-5-nitroindole (36) are determined to be 9.8, 8.4, 8.2, 8.1, 6.9, and 6.8, respectively (Fig. 2) (2000H1881). Thus, 1-hydroxyindoles are weak acids, stronger than phenol and weaker than succinimide. Therefore,... 

In the presence of DCC, 140 is allowed to react with both l-hydroxy-5-nitroindole (36) and 1-hydroxy-1,2,3-benzotriazole (141). Interestingly, their corresponding active esters, 142 and 143, are obtained in excellent yields as stable crystalline compounds. Both compounds are found to react with variety of nucleophiles, such as alcohols and amines, to produce 144 and 145 in good to excellent yields, as can be seen from the typical examples shown in Scheme 22 (2001H2361). As aresult, it becomes possible to produce various kinds of derivatives of wasabi phytoalexin utilizing 142 and 143. 

CfjHftNjOj 6146-52-7) see Zafirlukast 5-nitroindole-2-carboxyllc acid (C9HftN204 16730-20-4) see Delavirdine mesilate nitromethane... 

Nitroindole 418 Nitrophenyl isocyanate reagent 77 1-Nitropyrene 61 N-Nitrosamines 107... 

Deprotonation of benzimidazole can be studied onlyiin dilute NaOH, but deprotonation of 5-nitroindole and 5-nitroindole-2-carboxylate ion can be followed in 0.01-0.1 M NaOH in both CTABr and CTAOH. For CTAOH the concentration of micellar bound OH- was estimated from (19), and values of K] were similar in both CTABr and CTAOH micelles (Cipiciani et al., 1983b, 1985). 

In Figure 4.70, in the overall process, 5-nitroindole is reduced to amino-indole the chloride ion is present in the form of HG1 and the 5-nitroindole is protonated under these acid conditions. 

Substitution for PABA in a FA analogue by an indole ring has been accomplished by a Russian group Scheme 3.159) [290], Thus, acylation of dimethyl glutamate with 5-nitroindole-2-carbonyl chloride followed by catalytic hydrogenation furnished (701) which was condensed with (11) to yield imine (702). This was reduced with sodium borohydride to give (703) uneventfully. 

The nitration of indole (14a) in acetic anhydride occurs in both the pyrrole and the benzene rings to produce 3,6-dinitroindole (15), whereas in sulfuric acid, in which the conjugate acid is the reactant, nitration occurs to yield 5-nitroindole (16) (63JOC2262 64TL803). 

Noteworthy, imine 77 is slightly cyclized into 2-phenyl-5-nitroindole 79 in the presence of a base (Scheme 23) (04T247). This is probably due to the reduced electro-philicity of the benzene ring in intermediate anion 78. No cyclization of 78 at the position para to the nitro group has been observed. 

Nitroindole-2-carboxylic acid (0.86 g), l-[3-(N-isopropyl)amino-2-pyridinyl]piperazine (0.43 g), l-(ethyl)-3-(dimethylaminopropyl)carbodiimide (0.45 g) and THF (4 ml), were stirred at 20-25°C for 3 hr then the reaction mixture was dissolved in chloroform (50 ml) and extracted with saturated aqueous sodium bicarbonate, saline, dried over anhydrous sodium sulfate and concentrated under reduced pressure. Purification by flash column chromatography (200 g silica) eluting with ethyl acetate/hexane (50/50), the appropriate fractions were pooled and concentrated to give l-[5-nitroindolyl-2-carbonyl]-4-[3-(l-methylethylamino)-2-pyridinyl]piperazine, mp 153°-154°C. 

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