Hydroxylamines as reagents

J. L. Romine, Bis-Protected Hydroxylamines as Reagents in Organic Synthesis. A Review Org. Prep. Proced. Int. 1996, 28, 249-288. 

This means that, instead of one expected product with molecular weight (MW) = Mq + 29 (with O-methyl hydroxylamine as reagent), reaction mixtures may contain two additional compounds with MW = Mq + 47 and Mq + 76. This feature is negligible for analysis of individual compounds, but when samples are mixtures of components of interest, the analysis becomes impossible because of the complexity of the resultant interpretation. 

Another more environmentally friendly alternative for the spectrophotometric determination of the phenolic index is based on the use of solenoid micropumps as microfluidic handling devices, using nitroprusside/hydroxylamine as reagents, instead of 4-AAP/ferricyanide [189]. 

Metal hydrides such as LiAlH4 67 DIBAL is and NaBH4 in the presence of Te , Se °, NiCli or BiCls reduce nitro compounds into hydroxylamines, although they are not usually considered as reagents of choice for this reduction. 

There are a few reports on the use of oximes as electrophilic amination reagents. Since 1984, ketone O-sulfonyloxknes have found applicability as amino transfer reagents to car-banions. In the reaction of organometaUic compounds with oximes, carbanions attack the carbonyl carbon of the oxime, giving Af-substituted hydroxylamines as addition products (Scheme 53, path a). However, a number of scattered reports have been also published on the formation of aziridines by a-deprotonation, followed by addition (path b) or formation of azirines by a-deprotonation before addition (path c). Addition of carbanions to azirines also yields aziridines, which are hydrolyzed to a-aminoalcohols. 

The precipitation of cuprous acetylide was introduced into analytical chemistry for the quantitative determination of copper. Since cupric acetylide was dangerous to handle, Makowka [108] worked out a method in which cupric salts are previously reduced, e.g. with hydroxylamine, to cuprous salts, when the acetylide is precipitated. Cuprous salts in a solution of hydroxylamine are employed as reagents for acetylene (e. g. Pietsch and Kotowski [114]). 

Figure 1.19 Mass spectra of acetaldehyde PFB-oxime (a), diacetyl mono PFB-oxime (b), acetoin PFB-oxime derivative (c), and o-chlorobenzaldehyde PFB-oxime (d) recorded in the GC/MS analysis of standard solution performed in positive ion chemical ionization mode using methane as reagent gas (reagent gas flow 1 mL/min ion source temperature 200 °C). Flamini et al., (2005) Monitoring of the principal carbonyl compounds involved in malolactic fermentation of wine by synthesis of 0-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine derivatives and solid-phase-microextraction positive-ion-chemical-ionization mass spectrometry analysis, Journal of Mass Spectrometry, 40, p. 1561. Copyright John Wiley Sons, Ltd. Reproduced with permission...

Methylthio-l,2,4-triazin-5(2//)-ones (194) can be aminated regioselectively with 0-(2,4-dinitrophenyl)hydroxylamine as an amino-transfer reagent to give 2-amino-3-methylthio-1,2,4-triazin-5(2//)-ones (195) (Scheme 38). Reaction of the products (195) with amines followed by ring closure with aliphatic acids provided [l,2,4]triazolo[2,3-6][l,2,4]triazin-7(l//)-ones (196) <82JHC1583, 83JHC1671>. 

There is extensive history on the use of stoichiometric and catalytic organic nitroxyls for alcohol oxidation, wherein the key step involves a reaction between the alcohol and an JV-oxoammonium salt (Scheme 15.5, featuring TEMPO) [18, 20]. The JV-oxoammonium salt can be formed in situ from the corresponding nitroxyl radical using various oxidants, such as NaOCl or NO2 (Scheme 15.5, top left), or by acid-induced disproportionation of the nitroxyl into N-oxoammonium and hydroxylamine species (Scheme 15.5, bottom left) [21]. Stable Af-oxoammonium salts have also been isolated and used directly as reagents or catalysts for alcohol oxidation [22]. The pH-dependent mechanism of the reaction of the Af-oxoammonium salt with alcohols has been studied... 

Oxone has also been recently more thoroughly studied as reagent for the oxidation of aldehydes. Aryl- and aliphatic aldehydes can be efficiently converted directly to acids or esters depending on the choice of solvent (eq 34). They can also be converted to nitriles in one pot by reaction with hydroxylamine on alumina with microwave irradiation (eq 35). ... 

CN group exchange Amines 2-Hydroxybenzaldehyde azine used as reagent. Binary mixtures of hydrazine, hydroxylamine, and ammonia can be resolved. In all cases 2-hydroxybenzaldehyde hydrazone is formed, which is fluorimetrically detected... 

Hydroxylamine and its salts are used in various branches of industry, as reducing agents in color-film developers or as reagents in laboratories. 

The presence of anhydride intermediates during the course of the hydrolysis of sulfite esters catalyzed by pepsin was proposed by May and Kaiser (14). Studies of the catalysis of sulfite ester hydrolysis by model carboxylate species indicated that the presence of anhydride intermediates could be detected in such reactions by the use of nucleophilic trapping reagents (17). Based on the results of the model studies, we were encouraged to attempt to trap the hypothetical anhydride intermediates formed in the pepsin-catalyzed hydrolysis of a sulfite ester using hydroxylamine as the trapping agent, which could lead to the identification of the active sites involved in this reaction. 

Amide Synthesis Using Hydroxylamine as Nitrogenation Reagent... 

Obviously the concerted addition step is not possible when the nucleophile is 0-methylhydroxylamine due to the absence of a proton attached to the oxygen atom. This fact would explain the lack of reactivity observed when 0-methyl-hydroxylamine was employed as reagent. 

B. Mix 1 drop or several small crystals (ca. 0 05 g.) of the compound with 1 ml. of 0-5 V hydroxylamine hydrochloride in 95 per cent, ethanol and add 0-2 ml ot aqueous sodium hydroxide. Heat the mixture to boiling and, after the solution has cooled slightly, add 2 ml. of N hydrochloric acid. If the solution is cloudy, add 2 ml. of 95 per cent, ethyl alcohol. Observe the colour produced when I drop of 6 per cent, ferric chloride solution is added. If the resulting colour does not persist, continue to add the reagent dropwise until the observed colour pervades the entire solution. Usually only 1 drop of the ferric chloride solution is necessary. Compare the colour with that produced in test. 4. A positive test will be a distinct burgundy or magenta colour as compared with the yellow colour observed when the original compound is tested with ferric chloride solution in the presence of acid. 

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