O-Nitrocinnamic acid

This procedure has been used by the submitters and others to prepare the following cinnamic acids from substituted benzal-dehydes o-nitrocinnamic acid (70%),2 -nitrocinnamic acid (77%),2 w-cyanocinnamic acid (71%),3 o-chlorocinnamic acid (82%),4 m-chlorocinnamic acid (53%),4 -chlorocinnamic acid (73%),4 2,4-dichlorocinnamic acid (70%),4 3,4-dichlorocinnamic acid (81%),4 w-bromocinnamic acid (31%),4 -methoxycinnamic acid (60%),4 and 3,4-dimethoxycinnamic acid (77%).4... 

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. 

Formula 491) (222) and o-nitrocinnamic acid (Formula 492) gives Formula 493 (223). 

Another synthetic route proposed by von Baeyer began with o-nitrocinnamic acid (7) and led to o-nitrophenylpropiolic acid (8), which could be converted to indigo directly on the textile fiber with mild reducing agents under alkaline con-... 

Scheme 9.11 Hydrogenation of o-nitrocinnamic acid and ester over Raney Ni.

From or via o-substituted cinnamoyl derivatives. or/ -Substituted benzenes of type 93 (Z = 0, S, NH) can undergo ring closure (Scheme 61). Amines of type 93 (Z = NH), which usually cyclize spontaneously, are often prepared in situ by reduction of nitro compounds, e.g., o-nitrocinnamic acid with (NH4)2S gives 2-quinolone. 

Degradative oxidation of unsaturated carboxylic acids leads either to aldehydes or to dicarboxylic acids. In the presence of sodium carbonate and benzene, o-nitrocinnamic acid is oxidized with potassium permanganate at 10 °C to o-nitrobenzaldehyde in 64% isolated yield [842]. 

Condensation catalyst. Triethylamine serves as basic catalyst for the Perkin condensation of o-nitrobenzaldehyde with phenylacetic acid and acetic anhydride to give a-phenyl-trans-o-nitrocinnamic acid. A student experiment on the condensation of benzaldehyde with the same reactants includes a simple procedure for the separation of the cis- and /rans-isomers. ... 

N-Phenyl-/y-naphthylamine, 336, 846 trans Phenyl-o-nitrocinnamic acid, 1200 Phenylnitromethane, 691, 822 vPh iylnonanoic acid, 707-708 Phenylnorcarane, endo- and exo-, 1250-1251 Phenylosazones, 694,1099 5-Phenyl-1,4-pentadienaI, 669 8-Phenyl-2,4-pentadienic anhydride, 794... 

The reduction is effected by adding to the substance to be reduced, in tire presence of an alkali (potassium-, sodium-, or barium-hydroxide), a weighed quantity of ferrous sulphate. By this reaction, o-nitro-benzaldehyde is reduced to o-amidobenzaldehyde o-nitrocinnamic acid to o-amidocinnainic acid. 

A solution of 90 g of F62S04-7H20 (0.324 mol), 150 g of Ba(0H>2-H20 (0.79 mol) and 10 g of o-nitrocinnamic acid (0.052 mol) in 2 L of water in an Erlenmeyer flask was heated while stirring for 1 h. A red-brown precipitate of Fe(III) hydroxide formed and was filtered out. A stream of carbon dioxide was passed through the solution. The precipitate of BaC03 was filtered, the solution evaporated under vacuum, the residue treated with excess cone. aq. HCl and refluxed for 10 h. On cooling and neutralizing with cone. aq. ammonia carbostyril precipitated out as almost colorless crystals, mp 193 - 195 °C (4.5 g, 58% yield). 

Baeyer synthesised indole by reduction of o-nitrocinnamic acid with iron and potassium hydroxide (Baeyer-Emmerling indole synthesis). 

Baeyer and A. Emmerling suggested that indole would result if in benzene a two-membered carbon chain and an atom of nitrogen are introduced, and the two linked together . By fusing o-nitrocinnamic acid with caustic potash and some iron turnings they synthesised indole they formulated the reaction ... 

Synthesis of indigo was a particular challenge for dyestuff chemists in the second half on the 19 th century. Adolf von Baeyer first successfully synthesized indigo in 1869, starting from o-nitrocinnamic acid. 

Similarly to o-nitroarylacetic acids (vide supra Scheme 3), o-nitrocinnamic acids also underwent the reductive cyclization when subjected to the treatment with ammonium formate and zinc dust in supercritical CO2 [19]. In this case, concomitant hydrogenation resulted in the formation of 3,4-dihydroquinolones 30 ( heme 18). 

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