Salicylic acid, 4-amino-, reaction with

Sulfasalazine Sulfasalazine, 5-[p-[(4,6-dimethyl-2-pyridinyl)sulfamoyl]phenylazo]sali-cylic acid (33.1.22), is a derivative of sulfapyridine drug described above and one of the few sulfanilamides in which the free amino group in the benzene ring is modified, and it is synthesized by an azo-coupling reaction of a diazo salt, which is synthesized by reacting sulfapyridine (33.1.21) with nitrous acid and salicylic acid alkaline media [24,25]. 

Titanium(iv) (d ).—K stopped-flow method has been used to study the reaction of Tpv substituted salicylic acids (salicylic, jff-resorcylic, and 5-nitro- and 5-amino-salicylic acids), and with diantipyrylmethane (L). Formation of mono-, bis-, and tris-complexes of L were investigated with structures [Ti(OH)2L] +, [Ti(OH)2L2] +, and [TiLal. The last reaction, involving the formation of the tris-complex, is the slowest step involved. 

The annulation of benzoic acids proceeds efficiently even with a reduced amount (5 mol %) of Cu(0Ac)2-H20 under air (Scheme 25.28). In particular, anthranilic and salicylic acids undergo the reaction smoothly to produce 8-amino- and 8-hydroxyisocoumarins [24], which are known to show a broad range of biological and photochemical properties. 

Similar azomethine ylides 48 are involved as key intermediates in the racemi-zation of optically active a-amino acids in the presence of a catalytic amount of aldehyde (83JOC843). Grigg confirmed this mechanism (83TL4457) and carried out the reactions of optically pure a-amino acids with salicyl- or o-methoxybenzaldehyde and maleic anhydride or N-phenylmaleimide in acetic acid. Cycloadducts of N-unsubstituted azomethine ylides 48 with dipolaropbiles were obtained only as racemates. These results indicate that the a-amino acids first produced the corresponding imine carboxylic acids with the retention of optical activity but these then undergo a tautomeric equilibration with N-protonated azomethine ylides 48 losing their optical purity. The ylides 48 were captured by several dipolaropbiles as racemic cycloadducts. As the imines of a-amino acids usually suffer spontaneous decarboxylation (as will be discussed later in Section (II,E), the formation of... 

If the reaction is carried out with potassium phenoxide, the isomer, p-hy-droxybenzoic acid is obtained between 100° and 150° dipotassium salicylate is formed in this case also, but it rearranges, completely at 200°, to p-hydroxy-benzoic acid. Addition of carbon dioxide to polyhydric phenols or amino-phenols occurs even in aqueous solution. 1-Naphthol is also amenable to the reaction. 

Similar azomethine ylides 48 are involved as key intermediates in the racemi-zation of optically active a-amino acids in the presence of a catalytic amount of aldehyde (83JOC843). Grigg confirmed this mechanism (83TL4457) and carried out the reactions of optically pure a-amino acids with salicyl- or... 

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