Aluminum nitro groups

Phthalic anhydride condenses with the aniline derivative in the presence of zinc or aluminum chlorides to yield the intermediate benzoyl-benzoic acid, which subsequently reacts with l,3-bis-V,V-dimethylaniline in acetic anhydride to yield the phthalide. The above compound gives a violet-gray image when applied to a clay developer. Clearly this synthesis is also very flexible and variations in shades of color formers have been obtained by varying the aniline components and also by using phthalic anhydrides substituted, for example, by nitro groups or chlorine atoms. Such products have excellent properties as color formers and have been used commercially. Furthermore, this synthetic route is of great importance for the preparation of heterocyclic substituted phthalides, as will be seen later. 

Aliphatic nitro compounds with the nitro group on a tertiary carbon were reduced to amines with aluminum amalgam [146 or iron [559]. 2-Nitro-2-methylpropane afforded ferf-butylamine in 65-75% yield [146. Even some secondary nitroalkanes were hydrogenated to amines. fra s-l,4-Dinitrocy-clohexane was converted to frans-l,4-diaminocyclohexane with retention of configuration. This may be considered as an evidence that the intermediate nitroso compound is reduced directly and not after tautomerization to the isonitroso compound [560] (see Scheme 54). 

Cleavage of a benzyloxy bond was also accomplished by treatment with sodium in liquid ammonia [640] or by refluxing with sodium and butyl alcohol [641]. On the other hand, aluminum amalgams reduced a nitro group but did not cleave benzyl ether bond in dibenzylether of 2-nitrohydroquinone [642]. 

In nitro aldehydes both the nitro group and the aldehyde group are readily reduced by catalytic hydrogenation. It may be difficult, if not impossible to hydrogenate either function separately. More dependable methods are reduction by alane [787] or by isopropyl alcohol and aluminum isopropoxide Meerwein-Ponndorf) [788] to nitro alcohols, and by stannous chloride [789, 790], titanium trichloride [590] or ferrous sulfate [218] to amino aldehydes Procedure 38, p. 214). 

The reduction of a dinitro ketone to an azo ketone is best achieved with glucose. 2,2 -Dinitrobenzophenone treated with glucose in methanolic sodium hydroxide at 60° afforded 82% of dibenzo[c,f [i 2]diazepin-l 1-one whereas lithium aluminum hydride yielded 24% of bis(o-nitrophenyl)methanol [575], Conversion of aromatic nitro ketones with a nitro group in the ring into amino ketones has been achieved by means of stannous chloride, which reduced 4-chloro-3-nitroacetophenone to 3-amino-4-chloroacetophenone in 91% yield [178]. A more dependable reagent for this purpose proved to be iron which, in acidic medium, reduced m-nitroacetophenone to m-aminoacetophenone in 80% yield and o-nitrobenzophenone to o-aminobenzophenone in 89% yield (stannous chloride was unsuccessful in the latter case) [903]. Iron has also been used for the reduction of o-nitrochalcone, 3-(o-nitrophenyl)-l-phenyl-2-propen-l-one, to 3-(o-aminophenyl)-l-phenyl-2-propen-l-one in 80% yield [555]. 

Amides containing nitro groups are reduced to diamino compounds with alane. A, A -Dimethyl-p-nitrobenzamide, on reduction with lithium aluminum hydride in the presence of sulfuric acid in tetrahydrofuran, gave 98% yield of dimethyl-p-aminobenzylamine [1117]. 

In organic chemistry this stabilizing effect is well known the stability of carbanions is known to be enhanced by nitro groups. The stability of the cyclopentadienide anion is increased by complexing with a typical Lewis acid so that it becomes less reactive. For example, ferrocene is not ionized in nitromethane solution. Addition of a Lewis acid such as aluminum chloride facilitates the occurrence of intramolecular race-mization (75) a process which is believed to involve ionic intermediates [16). This belief is supported by kinetic evidence and the failure of the reaction to occur in nearly inert solvents like methylene chloride and in those of high donidty. Whereas the former do not support the solvation of the cation formed in the process of ionization, the latter will react preferentially with the Lewis acid, which is then no longer available for the stabilization of the carbanion. 

Nitration of hydroxypropiophenone (7-1) followed by conversion of the phenol to its methyl ether by means of methyl iodide provides the intermediate (7-2) the nitro group is then reduced to the corresponding amine (7-3) by catalytic reduction. The newly introduced amine is then replaced by a nitrile group by successive conversion to the diazonium salt by means of nitrous acid followed by treatment with cuprous cyanide (7-4). Reaction with aluminum chloride removes the methyl ether to afford the ortho acylphenol (7-5). This is converted to the chromone (7-6) as above by reaction with benzoyl chloride and sodium benzoate. The nitrile is next hydrolyzed to the carboxylic acid (7-7) by means of sulfuric acid. The acid is then converted to its acid chloride by means of thionyl chloride and that treated with 2-(A -piperidyl)ethanol (7-8). There is thus obtained flavoxate (7-9) [8], a muscle relaxant whose name reflects its flavone nucleus. 

Aluminum chloride-catalyzed acylation may be accompanied by formation of ct complexes (i.e., thiophenes protonated by the very strong acid co-product HA1C14) (75JOU412). This will be more serious under any of the following conditions (1) the thiophenes contain electron-supplying groups, as they will then be better bases (2) solvents that do not contain nitro groups are used, because aluminum chloride is then not coordinated... 

Na2S-5H20 and sulfur (1 atom equiv.) in DMSO until the initial blue-green color turns to yellow. A tertiary nitro group is reduced by the reagent to the corresponding thiol and a polysulfide the latter compound is reduced to the thiol by aluminum... 

The structure and the stereochemistry of the 1,2- and 1,4-nitroacetamides were assigned on the basis of spectroscopic analysis and conversion of the 1,2-nitroacetamides to dihydroimidazoles. Variable syn or anti addition was observed depending on the structure of the alkene. Reduction of the nitro group to an amino function by aluminum amalgam allows stereoselective synthesis of vicinal monoacetylated diamines. 

This reaction has found little application to mercaptan syntheses since the mercaptans are usually as readily available (by other methods) as the disulfides. The S-S linkage is reduced by zinc in acetic or sulfuric " acid, lithium aluminum hydride, or metallic sodium. y-Hydroxy-propyl disulfide is reduced electrolytically in 70% yield. Reduction by sodium disulfide does not reduce the nitro group in the preparation of p-nitrothiophenol (65%), whereas zinc and acetic acid converts o-nitro-phenyl disulfide to o-aminothiophenol (90%). Disulfides made by the action of ammonium hydrogen sulfide on aldehydes are sources for difficultly available aromatic and heterocyclic mercaptans. The disulfides are reduced by aluminum amalgam and water. ... 

Sodium borohydride is a mild and selective reducing reagent. In ethanol solution it reduces aldehydes and ketones rapidly at 25°C, esters very slowly, and is inert toward functional groups that are readily reduced by lithium aluminum hydride carboxylic acids, epoxides, lactones, nitro groups, nitriles, azides, amides, and acid chlorides. 

For the synthesis of 13-hydroxysparteine the starting material was a-picoline iV-oxide (CXVIII) which was nitrated and the nitro group then replaced by benzyloxy. The action of acetic anhydride induced the Boekelheide rearrangement to the acetoxymethyl derivative CXIX. The latter, via the alcohol, the chloride, the cyanide, and the ester, was condensed with ethyl hydroxymethylenepyridylacetate to the quinol-izone CXX, hydrogenation and reduction of which with lithium aluminum hydride gave a separable mixture of hydroxysparteines. The... 

Other reductions. A mixed hydride of ratio 1 1 is superior to lithium aluminum hydride alone for the reduction of nitriles to amines. Unlike lithium aluminum hydride, the mixed reagent does not reduce nitro groups. Thus p-nitrobenzaldehyde is reduced by mixed hydride to p-nitrobenzyl alcohol in 75% yield. Whereas lithium aluminum hydride tends to remove halogen atoms, this reduction is retarded or prevented by the presence of aluminum chloride. Thus (8-bromopropionyl chloride is reduced by a 1 1 mixed hydride to 3-bromo-1-propanol in 77% yield in the absence of AlClj the yield is 44%. ... 

The commercial dinitrophenol mixture is produced by heating phenol with dilute sulfuric acid, cooling the product, and then nitrating while keeping the temperature below 50 °C, or by nitrating with a mixed acid under careful temperature control (Sax and Lewis 1987). 2,3-, 2,5-, and 3,4-DNP are prepared by nitration of m-nitrophenol. 3,5-DNP is prepared by the replacement of one nitro group by methoxyl in 1,3,5-trinitrobenzene and demethylation of the dinitroanisole by anhydrous aluminum chloride. 2,6-DNP is prepared by sulfonation and nitration of o-nitrophenol (Harvey 1959). 2,6-DNP is also produced as a byproduct in the synthesis of 2,4-DNP by way of 2,4-dinitrochlorobenzene. 

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