Reduction aminobenzaldehyde

For the reduction of nitro-compounds containing a group which may be attacked by nascent hydrogen, as, for example, an aldehyde group, an unsaturated side chain, and so on, special methods must he applied. In such cases ferrous hydroxide or iron powder (cf. Chap. VII. 5, arsanilic acid) are often used. The reduction is carried out thus a weighed amount of ferrous sulphate is caused to act, in the presence of alkali (potassium or sodium hydroxide, baryta), on the substance to he reduced. In this way it is possible to reduce, for example, o-nitro-benzaldehyde to aminobenzaldehyde, and o-nitrocinnamic acid to amino-cinnamic acid. 

Amide reduction with lithium aluminum hydride, 39, 19 Amine oxide formation, 39, 40 Amine oxide pyrolysis, 39, 41, 42 -Aminoacetanilide, 39, 1 Amino adds, synthesis of, 30, 7 2-Amino-4-anilino-6-(chloro-METHYl) -S-TRIAZINE, 38, 1 -Aminobenzaldehyde, 31, 6 hydrazone, 31, 7 oxime, 31, 7 phenylhydrazone, 31, 7 > -Aminobenzoic add, 36, 95 2-Aminobenzophenone, 32, 8 c-Aminocaproic acid, 32, 13 6-Aminocaproic acid hydrochloride,... 

This reaction is particularly useful in the Fricdlander quinoline synthesis, the use of which has been limited hy the inaccessibility of o-aminobenzaldehydes. Thus a one-pot synthesis of quinolines is now possible by reduction of an o-nitrobenz-aldehyde with the reagent in the presence of an a-mcthylene ketone. 

Much more spectacular were the selectivity variations in the case of 3-nitro-benzaldehyde reduction (Table 3). Depending on the hydrogen donor used 3-nitro-benzyl alcohol (methanol, 450°C) or 3-aminobenzaldehyde (i-propanol, 450°C) were the main reaction products. 

Tetrabromo-4,4-Dinitramir>o Benzafa-zine (Azine). [02N2H.C6H2Br2.CH N -2 mw 643.88 N 13.06% OB toC02 -69.58% colorl ndles (from ethanol) mp, explds when heated. Prepn is by diazotization and reduction of 3,5-dibromo-4-aminobenzaldehyde (Ref 2) followed by nitration (Ref 3)... 

Other functional groups may be present during reduction. Aromatic amino ethers are prepared by the same general procedures described above, e.g., 772-aminoanisole (80%) and 2-aminodiphenyl ether (94%). The reduction of o-nitrobenzaldehyde to the sensitive o-aminobenzaldehyde is successfully accomplished by the action of ferrous sulfate and ammonia (75%). m-Dimethylaminobenzaldehyde is formed by reduction of the nitro acetal in aqueous solution with sodium sulfide followed by methyla-tion (74% over-all) or by catalytic reduction of m-nitrobenzaldehyde in... 

An alternative method of studying the reaction is by dinitrophenylation of the acid hydrazides (see above). The DNP derivatives are red in alkali and can be determined colorimetrically. Gallop et al. (1959) first used hydrazine to demonstrate ester links, but gave few details except that the fall of molecular weight was similar to that produced by hydroxylamine. The bound hydrazides were demonstrated by the reaction with p-dimethyl-aminobenzaldehyde, by dinitrophenylation, and by reduction of copper salts. 

A peculiar oxido-reductive reaction takes place when p-aminotoluene is heated with sodium polysulfide the product is p-aminobenzaldehyde [505]. 

Reductive oxidation of />-nitrotoluene to -aminobenzaldehyde, 31, 6 Reformatsky reaction, 37, 38 Reissert s compound, 38, 58 Reissert reaction, 38, 58 Replacement, benzenesulfonate groups by bromine atoms, 31, 82 bromine, by a thiol group, 30, 35 by fluorine, 36, 40 chlorine, by an amino group, 31,45 by a thiol group, 32, 101 by iodine, 30, 11 by methoxyl, 32, 79 by nitrile, 36, 50 in an imido-chloride group by an anilino group, 31, 48 chlorine and nitro by ethoxyl radicals, 32,68... 

Use of ferrous sulfate in an alkaline medium for the reduction of an aromatic nitro group ortho to a carbonyl function was introduced by Claisen and extended by Bamberger." A modern version is a procedure for the reduction of o-nitrobenzalde-hyde to o-aminobenzaldehyde. ... 

The 1,3-dihydro derivatives were prepared from benzisoxazolium cations by NaBiHU reduction (Scheme 188). Subsequent heating produced an aminobenzaldehyde (75USP3911132, 70JOC2440). Hydrogenation of quinoid, 3,5-dihydro-2,l-benzisoxazole, produced the 1,3-dihydro analog (Scheme 188) (73JCS(Pl)4372>. 

N-r-Butylbenzisoxazolines (170 R1 = t-Bu, R2 = H, R3 = Ar), prepared by sodium borohydride reduction of the anthranilium salts (see Section III,D), on heating at 150- 160°C isomerize to o-t-butylaminoacylbenzenes.233 The reaction has merit as a preparative route to o-aminobenzaldehydes, especially as only neutral conditions are employed. 

Cyclohex-2-en-l-one was converted initially to cyclohexanone but this was subsequently reduced at a rate comparable to the rate of appearance of the cyclohexanol e.g. after 30 min there was 40% reduction of the enone to equal amoimts of the saturated ketone and alcohol, while after 48 h there was 73% conversion of enone to essentially just cyclohexanol - no cyclohexen-l-ol was detected (10). Nitrobenzene was reduced selectively to aniline, but the conversion was only 20% after 48 h, while 4-nitrobenzaldehyde gave a mixture of mainly nitrobenzyl alcohol and smaller amounts of aminobenzyl alcohol and the aminobenzaldehyde. Heptan-l-al was also reduced to heptan-l-ol, while benzaldehyde under such basic conditions imderwent the Cannizzaro reaction to give the alcohol and benzoate. The findings summarized in this paragraph are all reproducible, while a notable transfer hydrogenation of oct-l-ene to octane noted in the earlier commimication has not been duplicated this will be commented on later. 

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