2- Nitrobenzaldehyde

Checked by John H. Sellstedt, Wayland E. Noland, and William E Parham 

o-Nitrobenzylpyridinium bromide. A 1-1. flask fitted with a reflux condenser is charged with 102 g. (0.744 mole) of o-nitro-toluene, 120 g. (0.675 mole) of N-bromosuccinimide, 1.0 g. of benzoyl peroxide, and 450 ml. of dry carbon tetrachloride. The mixture is heated under reflux until, after the refluxing is temporarily interrupted, all the solid is seen to float on the surface (usually 6-8 hours suffices). 

The hot mixture is filtered with suction into a 1-1. round-bottomed flask through a Buchner-type sintered glass funnel provided with a ground joint (Note 1). The solid on the funnel is washed successively with two 50-ml portions of hot carbon 

The solution is heated at the reflux temperature for 45 minutes and immediately transferred to a wide-mouthed Erlenmeyer flask. Crystallization begins at once, and, after the mixture is cooled, the crystals of nearly pure o-nitrobenzylpyridinium bromide are collected, washed with cold ethanol, and used in the next step (Note 4). 

o-Nitrobenzaldehyde. The wet crude nitrone is placed in a 3-1. beaker. A hot solution of approximately 6N sulfuric acid (Notes 8, 9) is then added, and the mixture is hand-stirred with a spatula or a glass rod. Crushed ice is added after 10 minutes, and the crude solid o-nitrobenzaldehyde is filtered, washed successively with dilute sodium bicarbonate solution and water, and dried over calcium chloride in a desiccator. 

Equip a 1 litre three-necked flask with a mechanical stirrer and a thermometer, and immerse the flask in a bath of ice and salt. Place 306 g. (283 ml.) of acetic anhydride, 300 g. (285 ml.) of glacial acetic acid and 25 g. of p-nitrotoluene in the flask, and add slowly, with stirring, 42-5 ml. of concentrated sulphuric acid. When the temperature has fallen to 5°, introduce 50 g. of A.R. chromic anhydride in small portions at such a rate that the temperature does not rise above 10° continue the stirring for 10 minutes after all the chromium trioxide has been added. Pour the contents of the flask into a 3 litre beaker two-thirds filled with crushed ice and almost fill the beaker with cold water. Filter the solid at the pump and wash it with cold water until the washings are colourless. Suspend the product in 250 ml. of cold 2 per cent, sodium carbonate solution and stir mechanically for 10-15 minutes filter (1), wash with cold water, and finally with 10 ml. of alcohol. Dry in a vacuum desiccator the yield of crude p-nitrobenzal diacetate is 25 g. (2). 

Reflux a mixture of 22-5 g. of crude p-nitrobenzal diacetate, 50 ml. of alcohol, 50 ml. of water and 5 ml. of concentrated sulphuric acid for 30 minutes, filter through a fluted paper, and cool the filtrate in ice. Collect the crystals by suction filtration, wash with cold water, and dry in a vacuum desiccator. The yield of p-nitrobenzaldehyde, m.p. 106° is 12 g. (3). 

Heat a suspension of 22 g. of the diacetate in a mixture of 120 ml. of concentrated hydrochloric acid, 190 ml. of water and 35 ml. of alcohol under reflux for 45 minutes. Cool the mixture to 0°, filter the solid with suction, and wash with water. Purify the crude aldehyde by rapid steam distillation (Fig. II, 41, 3) collect about 1500 ml. of distillate during 15 minutes, cool, filter, and dry in a vacuum desiccator over calcium chloride. The yield of pure o-nitrobenzaldehyde, m.p. 44-45°, is 10 g. The crude solid may also be purified after drying either by distillation under reduced pressure (the distillate of rather wide b.p., e.g., 120-144°/3-6 mm., is quite pure) or by dissolution in toluene (2-2-5 ml. per gram) and precipitation with light petroleum, b.p. 40°-60° (7 ml. per ml. of solution). 

5-10 g. of recoverable ester. The yield given is the total yield. 

The difficulty in the preparation of methyl pyruvate is caused by the fact that this ester is very easily hydrolyzed and that the ester equilibrium is far on the side of the hydrolysis products. 

Other methyl esters can be made by this procedure. 

Methyl pyruvate has been prepared from the silver salt of pyruvic acid and methyl iodide,3 and from the free acid by the alcohol-vapor method without a catalyst.4 Pyruvic esters have also been prepared by the dehydrogenation of lactic acid esters.8 

Submitted by S. M. Tsang, Ernest H. Wood, and John R. Johnson. Checked by Lee Irvin Smith and J. W. Opie. 

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Oxaziridine formation by photoisomerization of nitrones was discovered almost simultaneously with the peracid procedure (58JOC65l>. The t-butyl nitrones of benzaldehyde and 4-nitrobenzaldehyde yielded about 90% of oxaziridines (254) and (255) on UV irradiation. 

Nitrobenzaldehyde, TMSOTf, CH2CI2, it, 75-97% yield. Dithiolanes are stable to these conditions. 

Reagents are also available to convert thiocarbonyl compounds back to carbonyls. Simple hydrolysis is the most common method for converting thiocarbonyls to carbonyls. Stirring thioketones with 4-nitrobenzaldehyde and a catalytic amount of TMSOTf gives the ketone. ... 

Spray solution 2 Dissolve 0.3 g 4-nitrobenzaldehyde in 10 ml 2-methoxyethanol (methylcellosolve). 

Synthetic pyrethroids with a-cyano ester group react with sodium hydroxide to yield hydrogen cyanide, which reacts with 4-nitrobenzaldehyde and 1,2-dinitrobenzene to yield a pink-colored derivative (o-quinonoid di-anion) according to the following scheme ... 

The degradation of 4-nitrotoluene by Pseudomonas sp. takes place by oxidation to 4-nitrobenzoate via 4-nitrobenzyl alcohol and 4-nitrobenzaldehyde (Haigler and Spain 1993 Rhys-Williams et al. 1993 James and Williams 1998). 

Figure 5.4-59. Heating rates versus MTmax, 4-nitrobenzaldehyde, 2-nitrobenzoic acid, 4-nitrobenzoic acid (plots drawn based on data from Grwer and Klais, 1988).

Zinc-mediated benzylation of carbonyl compounds in aqueous media was reported by Bieber.214 The benzylation of 4-nitrobenzaldehyde... 

Scheme 43) [92]. Reaction of dienophiles such as 4-nitrobenzaldehyde with linker 80 at high temperature gave Diels-Alder products. Dihydro-pyrans were released from the support by Bronsted or Lewis acid-nucleo-phile combinations in moderate to good yield with stereoselectivity for the anti isomer. 

In this particular system, 4-nitrobenzaldehyde dimethyl acetal is deprotected by the acid catalyst, followed by the addition of methyl vinyl ketone (MVK) in an amine-catalyzed Baylis-Hillman reaction to give the product (Scheme 5.14). A yield of 65% for the final product was observed when the catalysts described in Scheme 5.13 were used, compared with no observed yield for the reaction with their soluble analogs. 

A series of 11 nitrobenzaldehydes was examined by TGA, DSC and ARC techniques. Only 5-hydroxy-2-nitrobenzaldehyde decomposed exothermally in an unsealed container, but all did so in sealed capsules, under dynamic, isothermal or adiabatic conditions, with evolution of much gas. Initial decomposition temperatures in °C (compound, ARC value, and DSC value at lOVmin, respectively, followed by ARC energy of decomposition in kJ/g) were - 2-nitro-, 176, 220, 1.44 3-nitro-, 166, 218, 1.94 4-nitro-, 226, 260, 1.27 2-chloro-5-nitro-, 156, 226, 697 2-chloro-6-nitro-, 146, 220,. 832 4-chloro-3-nitro-, 116, 165, 1.42 5-chloro-2-nitro-, 240, 3-hydroxy-4-nitro-, 200, 4-hydroxy-3-nitro-, 200, 5-hydroxy-2-nitro-, 175, 3-methoxy-4-nitrobenzaldehyde, 245°C, -. 4-Nitrobenzaldehyde showed by... 

Aldehyde or ketone (5 g) (4-nitrobenzaldehyde, piperonal, naphthalene-2-carboxalde-hyde, 2-furan carboxyaldehyde, 2-thiophene carboxyaldehyde, propanal, butanal, piva-laldehyde or cyclohexanecarboxaldehyde)... 

The photochemistry of 4-nitrobenzaldehyde has been reinvestigated In aqueous solution, 4-nitrosobenzoic acid is formed. A ketene has been proposed as intermediate... 

Another example of sonochemical switching is found in the Kornblum-Russell reaction (Scheme 3.9). 4-Nitrobenzyl bromide reacts with 2-lithio-2-nitro-propane via a predominantly polar mechanism to give, as a final product, 4-nitrobenzaldehyde [57]. An alternative SET pathway exists in this reaction leading to the formation of a dinitro compound. Sonication changes the normal course of the reaction and gives... 

Russell and Danen (1968) studied the sonication effect on the reaction between the lithium salt of 2-nitropropane and 4-nitrobenzyl bromide. A dual mechanism, ionic and ion-radical, characterizes this reaction. The ionic mechanism leads to the 0-alkylation product and, eventually, to 4-nitrobenzaldehyde ... 

Experiments in deoxygenated ethanol solution in the dark showed that, by stirring, 4-nitrobenz-aldehyde is obtained in 60% yield, accompanied by 13% 2-(4-nitrobenzyl)-2-nitropropane. Under the same conditions, but with sonication, the yields are 23% of 4-nitrobenzaldehyde and 48% of 2-(4-nitrobenzyl)-2-nitropropane (Einhorn et al. 1990). The importance of this result consists in the following conclusion The ultrasonic irradiation has a marked influence on the relative rates of the competing reactions and stimnlates just the ion-radical one. 

As a rule, if the unpaired electron density in the anion-radical is redistributed, the rotation barrier decreases. Thus, the barrier of the phenyl rotation in the benzaldehyde anion-radical is equal to 92 kJ mol", whereas in the 4-nitrobenzaldehyde anion-radical, the barrier decreases to 35 kJ mor (Branca and Gamba 1983). Ion-pair formation enforces the reflux of the unpaired electron from the carbonyl center to the nitro group. Being enriched with spin density, the nitro group coordinates the alkali metal cation and fixes the unpaired electron to a greater degree. The electron moves away from the rotation center. The rotation barrier decreases. The effect was revealed for the anion-radical of 4-nitrobenzophenone and its ionic pairs with lithium, sodium, potassium, and cesium (Branca and Gamba 1983 Scheme 6.19). 

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