Para-nitrobenzaldehyde

In 1880, Otto Fischer synthesized rosaniline (aniline red) from para-nitrobenzaldehyde. However, the process was not of commercial value due to the difficulty in converting the colorless, reduced, leuco intermediate into the dyestuff. This was a problem with all novel syntheses of aniline red before 1900. Pararosaniline continued to be made by nitrobenzene oxidation of anilines, at least until around 1940, when condensation of aniline with formaldehyde came into more general use. 

Taillefer et al. have reported a one-pot method for the preparation of a, 3-unsaturated organophosphorus compounds through the reaction of lithium diphenylphosphonium diylides with phosphorus electrophiles and aldehydes. In the first step, treatment of diylides (91) with chlorodiphenylphosphine results in the formation of mono-ylide intermediates (92) and (93). Subsequent addition of aldehyde (94) produces either alkenes (95) or phosphines (96) (Scheme 22). The product obtained is critically dependent upon the nature of the ylide substituents and the aldehyde employed. For example, non-stabilised ylide (91a) reacts with chlorodiphenylphosphine and aromatic, heteroaromatic or enolisable aldehydes (94a-f) producing the corresponding phosphines (96), predominantly as the Z isomer. However, with 4-phenylcyclohexanone the only product obtained from (91a) is the alkene, (4-methylenecyclohex-l-yl)benzene. Non-stabilised ylide (91b) reacts with chlorodiphenylphosphine and benzaldehyde (94a) to give primarily alkene product whereas para-nitrobenzaldehyde (94c) yields only the phosphine product. Semi-stabilised ylide (91c), and stabilised ylide (91d), react... 

The relative adsorption of type 1 isomers on silica is somewhat less clear-cut than on alumina. The lesser importance of sample delocalization on silica [see Eq. (10-5a) and related discussion] should make site chelation on silica less significant than on alumina. Thus the ortho- and para-nitrobenzaldehydes, methoxybenzaldehydes, or dichlorobenzenes are adsorbed on silica to about the same extent (9,20,22a). However, the or// o-dinitrobenzenes, fiuoronitrobenzenes, or chloronitrobenzenes are adsorbed more strongly on silica than are the para isomers (22a,23), suggesting the importance of site chelation.f The relative adsorption on silica of the isomeric methyl esters of the benzene carboxylic acids (51) seems to be controlled by site-chelation. In each case that isomer which has the greatest number of adjacent ester groups is more strongly adsorbed ... 

R -.u.. (An azlactone) Hydantoin Draw the structure of the product that would be formed if each underwent the Perkin condensation with p-chlorobenzaldehyde. 6-121. para-Nitrobenzaldehyde reacts at a faster rate than benzaldehyde in the Perkin reaction, while p-N,N- ... 

Moreover, a water-compatible proline-derived thiourea-amine bearing a hydrophobic camphor scaffold was evaluated as an organocatalyst for the aldolisation of cyclohexanone with para-nitrobenzaldehyde, affording the aldol product with an excellent yield, an enantioselectivity of 99% ee and an excellent u t/-diastereoselectivity (Scheme 2.25). The reaction was carried out in the... 

A comparative study of the efficiency of chiral bimorpholine- and bipiperidine-type organocatalysts for asymmetric aldolisations was reported by Kanger et al. These chiral tertiary amines were investigated for both the aldolisation of acetone with para-nitrobenzaldehyde and the intramolecular aldolisation of triketones. In both cases of aldolisations, the bimorpholine derivatives were found to be more reactive as well as more selective than the corresponding bipiperidine derivatives, as summarised in Scheme 2.44. The intramolecular aldolisations yielded the Wieland-Miescher ketone and its analogue in enantioselectivities of up to 95% ee by using the bimorpholine-type catalyst combined with an additive such as TfOH, while the aldol product from acetone was isolated in the same conditions with enantioselectivities of up to 88% ee. 

The new target molecule is aldimine TM 5.3a, which is interconverted to para-nitrobenzaldehyde TM 5.3b by the logical FGI step. Aldehyde is a commodity available by the nitration of toluene and partial oxidation by chromium(IV) oxide in acetic anhydride. 

The difference in activity among the lanthanide salts was further demonstrated by the fact that para-nitrobenzaldehyde was not acetalized after 20 hr in the presence of erbium chloride, but was completely converted when ytterbium chloride was the catalyst. This is consistent with the observation that acetalization yields increased with increasing atomic number (decreasing ionic radius), a phenomenon related to the Lewis acidity (or degree of hardness) of the cations. The role of the lanthanide catalyst is not well-defined, however. 

Although the number of successful applications of primary amino acids in stereoselective organocatalysis is far fewer than for the secondary amine, a few interesting examples are worth pointing out. The diversity of primary amino acids in aldol and Mannich reactions has been reviewed recently [48]. Several primary amino acids, such as alanine, valine, tryptophan, and threonine have been used as orga-nocatalysts. For instance, Barbas and coworkers have demonstrated the use of a L-threonine catalyzed protocol towards the synthesis of syn-l,2-diols through direct aldol reaction between a-hydroxyketones and para-nitrobenzaldehyde (Figure 17.13) [49]. 

Houk and coworker have examined the stereoselectivily in a series of amino acids in an intramolecular aldol reaction using the DFT(B3LYP) computational tool [51]. They attributed increased conformational flexibility in the stereoselective bond forming transition state as the origin of the lower enantiomeric excess noted with acyclic primary amino acids. Himo, Cordova, and coworkers have used density functional theory computations to examine the stereocontroUing transition states for the (S)-alanine catalyzed intermolecular aldol reaction between cyclohexanone and para-nitrobenzaldehyde [52]. In a very recent study, Houk, Mahrwald, and coworkers compared the transition states of an asymmetric aldol reaction... 

During their studies on the Biginelli reactions of para-nitrobenzaldehyde, thiourea, and ethyl acetoacetate with the promotion of 10mol% of the nonenantiopure 3,3 -ditriphenylsilyl binol-derived phosphoric acid 5c in toluene, a strong positive nonlinear effect was observed. The asymmetric amplification was also found to occur in several other phosphoric acid-catalyzed reactions [14]. 

The methyl group of -nitrotoluene is activated by the para nitro group. -Nitrotoluene is oxidized to -nitrobenzoic acid [62-23-7] by potassium hexacyanoferrate(III) in alkaline solution, potassium permanganate, or potassium dichromate. -Nitrotoluene is converted to -nitrobenzaldehyde... 

In the presence of KOH, /m(benzotriazol-l-yl)methane 729 reacts with nitrobenzenes to produce />-(/fc (bcnzo-triazol-lyl)methyl]nitrobenzenes 730 (Scheme 114) <1996TL347>. This vicarious nucleophilic substitution of hydrogen <1991S103> can be considered as a convenient way to />-nitrobenzaldehydes 731. Meta and para substituted nitrobenzenes do not react with compound 729 under these conditions, probably due to steric reasons, but 1-nitronaphthalene reacts producing a naphthalene analog of derivative 730. 

If benzaldehyde diacetate is the starting material, the amount of ortho- and para-nitration increases 198 nevertheless o- and />-nitrobenzaldehyde are pre-... 

Aromatic aldehydes bearing either electron-releasing or electron-withdrawing substituents in the ortho-, meta-, or para-positions proceeded very efficiently, except with 4-nitrobenzaldehyde. The reactions offer noncorrosiveness, safety, low waste, ease of separation, and high yields. 

Aldehydes in the ortho position were consistently poor substrates for carbinol production. Aldehydes with -CH3, -CF3 and -Cl substituents located in the para position produced higher carbinol yields than their meta counterparts. The opposite was the case with -OCH3 substituent. p-Nitrobenzaldehyde, cinnamaldehyde, and salycyl aldehyde did not appear to produce carbinol products. The highest carbinol yield was observed with benz-aldehyde substrate (10.1-10.2 mg/ml). The yields obtained for other aromatic aldehydes suggested that this was an efficient system for bioconversion of ring-substituted benzal-dehydes to corresponding carbinols. 

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