2-Hydroxybenzaldehyde oxime

Reactions with Amines and Amides. Hydroxybenzaldehydes undergo the normal reactions with aUphatic and aromatic primary amines to form imines and Schiff bases reaction with hydroxylamine gives an oxime, reaction with hydrazines gives hydrazones, and reactions with semicarbazide give semicarbazones. The reaction of 4-hydroxybenzaldehyde with hydroxylamine hydrochloride is a convenient method for the preparation of 4-cyanophenol (52,53). 

Hydroxybenzaldehyde has extensive use as an intermediate in the synthesis of a variety of agricultural chemicals. Halogenation of Nhydroxybenzaldehyde, followed by conversion to the oxime, and subsequent dehydration results in the formation of 3,5-dihalo-4-hydroxybenzonitrile (2). Both the dibromo- and dhodo-compounds are commercially important contact herbicides, hromoxynil [1689-84-5] (2) where X = Br, and ioxynil [1689-83-4]( where X = I respectively (74). Several hydrazone derivatives have also been shown to be active herbicides (70). 

Trimethylphenol (221) was oxidized with dioxygen catalyzed by CuCl2-2H20 to afford 3,5-dimethyl-4-hydroxybenzaldehyde (222) and 2,6-dimethyl-p-benzoquinone (223) in low yields. However, the use of acetone oxime as an additive caused a dramatic change to afford both 222 and 223 in 91.5 and 6.5% yields, respectively . These oxidation products are formed from p-quinone methide 225 through 2,6-dimethyl-4-(hexyloxymethyl)phenol (224) (Scheme 45). 

Both compounds are made by the halogenation of 4-hydroxybenzaldehyde, conversion to the oxime and dehydration to the nitrile according to the following reaction scheme (Auwers and Reis, 1896) ... 

A useful application of trityl linkers involves anchoring one function of a symmetrical diol [70-73] or diamine [74,75], enabling subsequent transformations to be conducted on the second functional group before acid-induced cleavage. Trityl resins can be used for anchoring phenols, such as 4-hydroxybenzaldehyde, in the presence of pyridine. The product was transformed via an oxime into isoxazolines, which were cleaved from the resin using TFA-CH2CI2 (1 99) [76]. 

Inclusion of the phosphazene cross-linker increases the decomposition temperature of the polymer from 275 °C to approximately 370 °C, depending on cross-linker loading, which varied between 0.3 and 1.2 weight percent. Fluxes were found to decrease with increased cross-linker loading. The hydroxybenzaldehyde motif also provides a pathway to further functionalization as demonstrated in a report where the aldehyde functionality was successfully converted to an oxime. 

Amino-Alditols. - Aldose oximes, e.p... of mannose and arabinose, can be reduced electrochemically to 1-aminoalditols glucose oxime reacted differently, because, it is proposed, of its strong tendency to cyclize to an N-glucosyl hydroxylamine derivative. l-Amino-2-acetamido-1,2-dideoxy-D-alditols have been prepared by sodium cyano-borohydride reduction of 2-acetamido-2-deoxy-glycosylamines (D-Glc, D-Man, and D- lc-D-Glc).6-(5-deoxy-D-ribit-5-yl)amino-uracil has been condensed with 2-chloro-4-hydroxybenzaldehyde to give a flavin derivative which was further elaborated to Redox Coenzyme Factor 420. ... 

Another example is the nitrosation of creatinine in meat, by which 5-oxocreatinine-5-oxime and l-methyl-5-oxohydantoin-5-oxime can arise (Figure 12.32). Some phenols also react with nitrosation reagents yielding nitroso compounds and oximes. In addition to nitroso compounds and oximes, in reactions with nitrosation agents there also arise nitro, oxynitro and nitronitroso compounds, as in the case of polycyclic aromatic hydrocarbons (PAHs). The mechanisms of their formation and other aspects of their presence in food are not yet sufficiently known. An example is the nitrosation of p-coumaric acid, which is dependent on pH. Acidic pH results in 4-hydroxybenzaldehyde (16%), l d-dihydroxybenzeneacetaldehyde oxime (59%), 4-hydroxy-l -oxobenzeneacetaldehyde oxime (26%) and 7-hydroxy-l,2(4H)-benzoxazin-4-one (6%), whereas 4-(2-oxido-l,2,5-oxadiazol-3-yl)phenol was formed at acidic (6%) and neutral and alkaline pH (both 1%) (Figure 12.38). 

Benzoylhydrazone [3232-37-9]. Salicylaldehyde benzoylhydrazone. Hydrazo I C14H12N2O2 M 240.261 Used for fluorimetric detn. of A1 458 nm) as Me2CO soln. for photometric detn. of Ti, Cu, Pd extraction-photometric detn. of Co, Cu, Fe, Ni, Ti, V. Cryst. (MeOH aq.). Sol. EtOH si. sol. H2O. Mp 178°. Guanylhydrazone see 2-Hydroxybenzaldehyde guanylhydrazone, H-00105 Phenylthiosemicarbazone see 2-Hydroxybenzaldehyde phenylthiosemicarbazone, H-00107 Isonicotinoylhydrazone see Salinazid, S-00003 1-Phthalazinylhydrazone see 2-Hydroxybenzaldehyde I-phthalazinylhydrazone, H-00108 Me ether see 2-Methoxybenzaldehyde, M-00074 Oxime [94-67-7]. Salicylaldoxime C7H7NO2 M 137.138... 

Aminobenzoic acid [(2-hydroxyphenyl) methylenejhydrazide, A-00110 2-Hydroxybenzaldehyde A -(4-aminobenzoyl) hydrazone, H-00103 2-Hydroxybenzaldehyde 6-methyl-2-nicotinoylhydrazone, H-00106 2-Hydroxy nzoic acid [2-(2-pyridinyl) ethylidenejhydrazide, H-00121 2-(4-Hydroxyphenylazo)benzaldehyde Me ether, oxime, in H-00448 2,2 -Iminobisbenzamide, in 1-00013 2-Methyl-4-pyridinecarboxylic acid [(2-hydroxypheny 1) methylene] hydrazide, M-00272... 

---