Benzaldehyde-3-carboxyhc acid

Atophan. In a 1 litre round-bottomed flask, equipped with a reflux condenser, place 26 g. (24 ml.) of purified benzaldehyde (Section IV,115), 22 g. of freshly-distilled pyruvic acid and 200 ml. of absolute ethyl alcohol. Heat the mixture to the boiling point on a water bath and add slowly, with frequent shaking, a solution of 23 g. (22-5 ml.) of pure aniline in 100 ml. of absolute ethyl alcohol. The addition usually occupies about 1 hour. Reflux the mixture on a water bath for 3 hours, and allow to stand overnight. Filter off the crude atophan (1) at the pump and wash the crystals with a little ether. Recrystallise from ethyl alcohol (about 20 ml. per gram). The yield of pure 2-phenylquinohne-4-carboxyhc acid, m.p. 210°, is 30 g. 

Isocarboxazid Isocarboxazid, 2-benzylhydrazid-5-methyl-3-isoxazolecarboxylate (7.2.6), can be synthesized from acetylacetone, which on nitrosation with nitrous acid gives 5-methyl-isoxazol-3-carboxyhc acid (7.2.2). Esterification of this product gives the ethyl ester of 5-methyl-isoxazol-3-carboxyhc acid (7.2.3). The synthesized ester (7.2.3) is further reacted with benzylhydrazine, to give isocarboxazide (7.2.6), or with hydrazine, which forms 5-methyl-isoxazol-3-carboxylic acid hydrazide (7.2.4). Reacting the latter with benzaldehyde gives hydrazone (7.2.5), which is further reduced to the isocarboxazide (7.2.6) [46,47]. 

The reagent RuClj/aq. H2O2/AcOH/80°C oxidised several benzaldehydes to the corresponding carboxyhc acids [717], With RuClj/TBHP/C H nitriles RCH CN were converted to acyl cyanides [752], and side-chains of alkylaromatic compounds were oxidised by RuCyaq. H2O2/(DDAB)/80°C to aldehydes, ketones or alcohols (Table 4.1) [362]. 

For the synthesis of highly defined and complex polymer architectures, the Ugi-4CR serves as conjugation method for two kinds of polymers benzaldehyde-terminated PMMA and aniline-terminated PEG 5000 (Scheme 11) [73], For this purpose, the remaining components, isocyanide and carboxyhc acid, were added in high excess (ten and five equivalents, respectively) to achieve full conversion of the parent polymers. Removal of the excess was accomplished via dialysis. Attractively, this approach not only combines two different polymers, but also facilitates the synthesis of mid-functionalized block copolymers by simple introduction of functional isocyanides or carboxylic acids. In this way, Tao and coworkers introduced a fluorescent molecule via the carboxylic acid (using dansylglycine) or a terminal double bond (using 2-acrylamido acetic acid) to obtain a mid-vinyl PMMA-Z -PEG polymer. Mid-reactive polymers are known to behave differently to their end-functionalized counterparts due to the umbrella-effect [74]. Therefore, it was... 

Aldehydes are readily oxidized to carboxyHc adds using nitric acid of various concentrations. Aliphatic substrates can be appHed, however the selectivity is low and in the case of hydroxyaldehydes [133], the corresponding diadds are obtained. Aromatic aldehydes are smoothly converted into the corresponding carboxyhc acids [134]. Optimization studies revealed that a 5.5 molar solution of nitric acid was optimal for the conversion of benzaldehyde into benzoic add giving a 94% yield of the desired product [134]. Nitrogen heterocycles, and in particular phenanthroUnes containing aldehyde functions, are also readily oxidized by nitric acid to the corresponding carboxylic acids [135]. 

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