9-Nitro-5,6-dihydro- -3-oxid

Dibenzo[6,/][l,4]selenazocine, N-formyl-6,11-dihydro-synthesis, 6, 34l Dibenzoselenophene, 2-amino-diazotization, 4, 951 Dibenzoselenophene, 2-nitro-reduction, 4, 951 Dibenzoselenophene, 3-nitro-5-oxide... 

Uracil, 5-methoxy-6-methoxymethyl-2-thio-synthesis, 3, 134 Uracil, 1-methyl-aminolysis, 3, 91 synthesis, 3, 110 Uracil, l-methyl-5,6-dihydro-synthesis, 3, 110 Uracil, 6-methyl-3-phenyl-synthesis, 3, 110 Uracil, 3-methyi-2-thio-synthesis, 3, 112 Uracil, 6-methyl-2-thio-oxidation, 3, 94 Uracil, 5-nitro-... 

Nitration of quinindoline gave the expected 9-nitro derivative (261). A single mononitro compound was formed from the 3,4-dihydro-jS-carboline, harmaline this was 6-nitroharmaline, since on oxidation it yielded 3-nitro-4-methoxybenzoic acid. 

Tile same methodology as mentioned for the preparation of (9) was applied for the synthesis of 8-nitro-l,6-naphthyridines. Heating diethyl N- 3-nitropyridin-4-yl)aminomethylenemalonate (12) in diphenyl ether yields ethyl 8-nitro-l,6-naphthyridin-4(lH)-one 3-carboxylate (13) (63JCS4237, 30%) and acid treatment of 4-( y, y-diethoxypropylamino)-5-nitro-2-(/3,/3 -trifluoroethoxy)-pyridine (14) gives in a similar way 8-nitro-5-(/3, /3-triflu-oroethoxy)-l,2-dihydro-l,6-naphthyridine (15, 76%). Subsequent oxidation with chloranil, acid hydrolysis, and methylation with methyl iodide gives 8-nitro-6-methyl-l,6-naphthyridin-5(6H)-one (16,63%) (81JHC941). 

The nitration of l,2,5-selenadiazolo[3,4-/] quinoline 77 with benzoyl nitrate affords the 8-nitro derivative 78, whereas methylation with methyl iodide or methyl sulfate afforded the corresponding 6-pyridinium methiodide 79 or methosulfate 80, respectively (Scheme 29). The pyridinium salt 80 was submitted to oxidation with potassium hexacyanoferrate and provided 7-oxo-6,7-dihydro derivative 81 or, by reaction of pyridinium salt 79 with phenylmagnesium bromide, the 7-phenyl-6,7-dihydro derivative 82. Nucleophilic substitution of the methiodide 79 with potassium cyanide resulted in the formation of 9-cyano-6,9-dihydroderivative 83, which can be oxidized by iodine to 9-cyano-l,2,5-selenadiazolo [3,4-/]quinoline methiodide 84. All the reactions proceeded in moderate yields (81IJC648). 

Methyl 5-methoxy-6,7-dimethyl-3-oxo-3,4-dihydro-2-quinoxalinecarboxylate Methyl 5-methoxy-6,7-dimethyl-3-oxo-3,4-dihydro-2-quinoxalinecarboxylate 1 -oxide Methyl 3-methoxy-2-quinoxalinecarboxylate 2-Methy l-3-( 1 -methylallyl)quinoxaline 2-Methyl-3-(2-methylallyl)quinoxaline 2-Methyl-3-methylaminomethylquinoxaline 5-Methyl-7-methylamino-8-nitro-2-phenylquinoxaline 5-Methyl-7-methylamino-8-nitro-3-phenylquinoxaline... 

A new approach to functionally substituted 4,5-dihydro-l,2,3-oxadiazole 2-oxides 134 has been described (Scheme 9) <2005RJ0120>. The method allows access to new derivatives and better access to the known derivatives that relied on difficult-to-prepare starting materials such as A -nitrosulfamides and A -nitro-2-cyanoethylalkylamines. 

This method is very useful for the construction of 1-substituted 3,4-dihydroisoquinolines, which if necessary can be oxidized to isoquinolines. A P-phenylethylamine (l-amino-2-phenylethane) is the starting material, and this is usually preformed by reacting an aromatic aldehyde with nitromethane in the presence of sodium methoxide, and allowing the adduct to eliminate methanol and give a P-nitrostyrene (l-nitro-2-phenylethene) (Scheme 3.17). This product is then reduced to the p-phenylethylamine, commonly by the action of lithium aluminium hydride. Once prepared, the p-phenylethylamine is reacted with an acyl chloride and a base to give the corresponding amide (R = H) and then this is cyclized to a 3,4-dihydro-isoquinoline by treatment with either phosphorus pentoxide or phosphorus oxychloride (Scheme 3.18). Finally, aromatization is accomplished by heating the 3,4-dihydroisoquinoline over palladium on charcoal. 

This route to the a-nitroso derivatives of the 7r-deficient heterocycles has permitted an exploration of their chemistry. They are extremely reactive and condense readily with 1,3-dienes to give 3,6-dihydro-l,2-oxazines (e.g. 99), and with aromatic amines in the presence of acid to give azo compounds (Scheme 86). This latter reaction is particularly useful in view of the instability of the corresponding 2-pyridinediazonium salts referred to above, which limits conventional access. The a-nitroso heterocycles are oxidized by ozone or sodium hypochlorite to the a-nitro compounds (Scheme 86) (82JOC553). 

In Gegenwart von 2-Amino-1-nitro-1 -alkenen liefern 3,4-Diacyl-furazan-2-oxide bei der Ther-molyseuber 3-Acyl-5-dimethylamino-4-nitro-4,5-dihydro-l,2-oxazole unter Abspal-tung von Dimethylamin 3-Acyl-4-nitro-l,2-oxazole455 ... 

I Kalium-7-methoxy-6-nitro-4,7-dihydro-benzofuruzun-1-oxid-4-nitronat... 

Wird 4-Nitro-benzofurazan-l-oxid mit Diazomethan umgesetzt, kann la-Nitro-la, 6a-dihydro-(cyclopropa[e benzofurazan)-4-oxid zu 20% isoliert werden344 ... 

Aryl-4,5-dihydro-l,2-oxazole aligemeine Arbeitsvorschrift2 0,02 mol (/ )-l-Nitro-l-alken in 20 m/ trockenem Ether werden tropfenweise unter starkem Riihren zu einer Losung von 0,01 mol Benzonitril-oxid in 80 ml trockenem Ether bei 0° gegeben. Nach 12 h Riihren bei 25° wird die Mischung 2 h zum RiickfluB erhitzt, i.Vak. eingeengt und dcr Riickstand i.Vak. destilliert oder umkristallisiert. 

Compound 378 has been made by oxidation of 6 -nitro-3,4-dihydro-papaverine (379) to the A-oxide 380 using hot ethanolic iodine solution... 

Ready addition of 2-nitrosopyridine to 1,3-dienes gives 3,6-dihydro-1,2-oxazines, e.g. (774) — (773), and condensation with aromatic amines gives azo compounds, e.g. (774) — (775). Nitroso compounds are oxidized by ozone or sodium hypochlorite to the corresponding nitro compounds. 5-Nitrosopyrimidines can be reduced to the 5-amino derivatives or condensed with activated methylene groups. 

Catalytic reduction of the 2-nitrophenyIhydrazones (745) and subsequent air oxidation of the tetrahydro-l,2,4-benzotriazines (746) which are formed is used for the synthesis of 3,4-dihydro-1,2,4-benzotriazines (747) (80FES715). In another cyclization of an o-nitro group, which somewhat resembles others (e.g. 736 —> 737) described earlier, treatment of l,l-dialkyl-2-(2-nitrophenyl)hydrazines (748) with acids affords 2-alkyl-1,2,4-benzotriazinium salts (749) (77JCS(P1)478). The 2-nitrophenylbromohydrazone (750) with sodium ethoxide and ethyl cyanoacetate forms 6-bromo-3-phenyl-l,2,4-benzotriazine (751) a mechanism for this interesting transformation, in which the cyanoacetate plays no part, has been proposed (79JHC33). 

An unexpected aromatization that takes place during the A-alkylation reaction performed on several 3-(2-nitrobenzoyl)-4,5-dihydro-l //-pyrazolc-5-carboxylic acid methyl esters, giving rise to a mixture of l-alkyl-3-(2-nitrobenzoyl)-4,5-dihydro-1 II-pyrazole-5-carboxylic acid methyl esters and 1 -al kyl-3-(2-ni trobcnzoyl)-1 //-pyrazole-5-carboxylic acid methyl esters is reported. It is suggested that reaction involves both inter- and intra-molecular oxidation by the nitro group.107... 

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