Nitrobenz.aldehydes

The reaction of 3-methyl-6-phenyl-l,2,4-tiiazine 4-oxides 117 with nitrobenz-aldehyde leads to the condensation product, 3-(nitrophenylvinyl)-1,2,4-triazine 4-oxides 118. 

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. 

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. 

A great many aldehydes can be employed—propaldehyde, nitrobenz-aldehyde, phenylacetaldehyde, furfurol—so that the reaction is of wide application. For the steps in the conversion of the compounds obtained to alkyl or aryl derivatives of dimethylpyridine, see pp. 242, 411, 412. 

Other aldehydes and related compounds have been reacted either alone or catalyzed with sulfuric acid, zinc chloride, magnesium chloride, ammonium chloride, or diammonium phosphate (94). Compounds such as l,3-bis(hydroxymethyl)-2-imidazolidone, glycol acetate, acrolein, chloroacetaldehyde, heptaldehyde, o- and p-chloro-benzaldehydes, furfural, p-hydroxybenzaldehyde, and m-nitrobenz-aldehyde all achieve the ASE by a bulking mechanism and not by low-level cross-linking. At weight gains of 15-25%, the highest ASE reported is 40%. 

Avoid sequences which may lead to unwanted reactions at other sites in the molecule. Thus nitration of benzaldehyde gives only 50% m-nitrobenz-aldehyde since the nitric acid oxidises CHO to CO2H. One way round this particular problem is to nitrate benzoic acid and reduce CO2H to CHO. 

In 1972, Jensen et al. reported that selenobenzoic acid reacts with m-nitrobenz-aldehyde to afford Sc-[hydroxyl(m-nitrophenyl)-methyl] selenobenzoate. The treatment of the acid in NaHC03 with p-nitrobenzyl bromide gave Se- p-m-trobenzyl) selenobenzoate [13]. In 1987, Hirabayashi et al. reported that 4-bi-phenylselenocarboxylic acid reacts with methanol, phenyl isocyanate and pyridine to give ArC(0)0Me,ArC(0)SeC(0)NHPh and ArC(0)NHPh, respectively (Ar=4-biphenyl) [15]. 

The coupling reaction of phenyl vinyl ketone (1.5 eq.) and p-nitrobenz-aldehyde was carried out at 25 °C wiA [Rh(COD)2]OTf (5mol%), PPhs (12 mol%), KOAc (50 mol%) under H2 (1 atm) atmosphere to give the aldol product 54 in 92% yield (Scheme 18) [31]. Omission of KOAc decreased the yield to 79%. The aromatic aldehydes gave the corresponding aldol products in good to excellent yields, whereas ahphatic aldehydes resulted in diminished yields. Methyl vinyl ketone as an enolate source can be tolerated, giving a 70% yield of the aldol product 58. 

Acetonitrile, L-tryptophan, ethylene glycol dimethacrylate (EGMA), /7-nitrobenz-aldehyde, acetic acid, AIBN, solution of 20% acetic acid in methanol, solution of 10% acetic acid in methanol, methanol, and CHCI3. 

A suspension of l,3-diphenyl-4-methyl-4-(4 -chlorophenylazo)-5-pyrazolone in glacial acetic acid treated with Zn-dust during 5 min., and stirring continued for 5 min. 4-chlorophenylhydrazine (Y 79% as the hydrazone of 4-nitrobenz-aldehyde) and l,3-diphenyl-4-methyl-5-pyrazolone (Y 75%). F. e. s. W. Pelz et al., Ang. Gh. 72, 967 (I960). 

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