Hydroxylamines from oximes

ZI N N E R Hydroxylamine Synthesis Synthesis of O-substituted hydroxylamines from oximes or hydroxamates. 

Imines are easily reduced and rarely accumulate (62,83). Hydroxylamines are reduced relatively slowly and can be obtained in good yield platinum in acidic media appears to be the preferred system (6,27,54,58,65). Best yields are obtained from oximes of aliphatic carbonyls aromatic oximes give amines. 

Arylisoxazol-5(4//)-oncs 21 react with benzene-1,2-diamines to yield 4-aryl-l,5-benzodiaze-pinones 22 by elimination of hydroxylamine from the intermediate oximes. Unsymmetrically substituted benzene-1,2-diamines are attacked at the more nucleophilic amino group. Thus, 4-methylbenzene-1,2-diamine gives 7-methylbenzodiazepinones 22f-h, whereas 4-nitrobenzene-1,2-diamine gives 8-nitro compounds 22k-n. The benzodiazepinones are accompanied by minor amounts of 2-methylbenzimidazoles 23. Selected examples are given.275... 

HPO [Hydroxylamine phosphate oxime] A process for making caprolactam, an intermediate in the manufacture of polyamides. It differs from related processes, such as HSO, in producing less of the ammonium sulfate by-product. Developed by DSM Research, The Netherlands, operated by DSM Polymers and Hydrocarbons, and offered for license by Stamicarbon. 

Two general mechanisms exist for NO release from oximes 1. hydrolysis to hydrox-ylamine followed by hydroxylamine oxidation and 2. direct oxidation and decomposition of the oxime. 

The common name caprolactam comes from the original name for the Ce carboxylic acid, caproic acid. Caprolactam is the cyclic amide (lactam) of 6-aminocaproic acid. Its manufacture is from cyclohexanone, made usually from cyclohexane (58%), but also available from phenol (42%). Some of the cyclohexanol in cyclohexanone/cyclohexanol mixtures can be converted to cyclohexanone by a ZnO catalyst at 400°C. Then the cyclohexanone is converted into the oxime with hydroxylamine. The oxime undergoes a very famous acid-catalyzed reaction called the Beckmann rearrangement to give caprolactam. Sulfuric acid at 100-120°C is common but phosphoric acid is also used, since after treatment with ammonia the by-product becomes... 

Nevertheless, the direct nucleophilic displacement of support-bound carboxylates to prepare hydroxamates presents some limitations. For example, O-tert-butyldimethylsilyl-protected hydroxylamine displaces common acids from oxime resin however, further treatment with trifluoroacetic acid (TFA) is necessary to remove completely the silyl... 

The in situ formation of nitrones from oximes by 1,3-APT or 1,2-prototropy is clearly a powerful synthetic strategy but conventional nitrone generation, in particular hydroxylamine-carbonyl condensation, has been applied to numerous syntheses, in intra- and intermolecular mode (258). Accordingly, the ring systems similar to those synthesized using 1,3-APT/intramolecular nitrone-alkene cycloaddition (INAC) methodology by Heaney (313-315) (see Section 1.11.2) or Padwa and Norman (340) have been made using conventionally prepared nitrones (Scheme 1.67). As with the previous examples, once formed, the nitrones are suitably placed for a spontaneous intramolecular cycloaddition reaction with the... 

Amarger, N., and Alexander, M. (1968). Nitrite formation from hydroxylamine and oximes by Pseudomonas aeruginosa. ]. Bacteriol. 95, 1651-1657. 

Partially methylated, acetylated aldononitriles are acyclic derivatives readily formed from reducing sugars by reaction with hydroxylamine in pyridine, followed by the addition of acetic anhydride to effect elimination of acetic acid from oxime acetates and acetylation of unsubstituted hydroxyl groups. These derivatives, although less extensively used, appear to give good GLC separations, and their mass spectra can be readily interpreted without the problem of structural symmetry (75MI3). 

N-oxidation can occur in a number of ways to give either hydroxylamines from primary and secondary amines [Eqs. (11) and (12)], hydroxamic acids from amides, or N-oxides from tertiary amines [Eq. (13)]. The enzyme systems involved are either cytochrome P450 or a flavoprotein oxygenase. Hydroxylamines may be further oxidized to a nitro compound via a nitroso intermediate [Eq. (11)]. Oximes can be formed by rearrangement of the nitroso intermediate or N-hydroxylation of an imine, that could in turn be derived by dehydration of a hydroxylamine [Eq. (11)]. N-Oxides may be formed from both tertiary arylamines and alkylamines and from nitrogen in heterocyclic aromatic systems, such as a pyridine ring. 

Benzil acts like a ketone in that it forms oximes with hydroxylamine-The oximes are of exceptional interest, since our knowledge of the stereochemistry of nitrogen proceeds from them. Benzil forms two monoximes and three dioximes. The constitution of these compounds will be discussed later, under the preparation of benzophenone-oxime ... 

The HPO (hydroxylamine phosphate oxime) process, developed byDSMand licensed by Siamicarbon, totally eliminates the production of ammonium sulfate, both in the production of hydroxylamine itself and in die oxime production stage. It consists of the catalytic hydrogenation of the nitrate ions resulting from the oxidation of ammonia to hydroxylamine ions in a solution buffered by phosphates. The nitrate reduction reaction is as follows ... 

As discussed in Section II,D,2, the action of hydroxylamine on o-acylcyclohexanones generally produces an inseparable mixture of 4,5,6,7-tetrahydro-1,2- and -2,1-benzisoxazoles, the latter, except in a few instances, being the major products.92-94,261 Synthesis of 4,5,6,7-tetrahydroanthranils free from contamination by indoxazenes is now possible by condensing esters with 1,4-dianions, e.g., 184, derived from oximes having an a-hydrogen, as exemplified in Scheme 24.262... 

Oxidation of N-O Compounds. The preparation of disub-stituted oxazolines from aldoximes has been accomplished via in situ nitrile oxide formation using Mn02 (eq 60). Oxidation of hydroxylamines and oximes to nitrones " and aldehydes/ ket- ones, respectively, has been found to occur upon treatment with Mn02 (eqs 61 and 62). 

This reaction was initially reported by Granacher in 1922. It is the preparation of thionic acid by the treatment of Aldol Condensation product from an aldehyde and rhodanine with a base (e.g., NaOH). Therefore, this reaction is known as the Granacher synthesis or Granacher reaction." The prepared thionic acid in this reaction can be further converted into a variety of derivatives under different conditions. For example, it can be transformed into a-thiol acid under a basic sodium amalgam reduction, whereas aliphatic acid is formed under an acidic zinc amalgam reduction. In addition, when the thionic acid is treated with ammonia, a-keto acid is generated, and the thionic acid can be converted into af-carboxyl oxime in reaction with hydroxylamine, from which either cy-amino acid or aliphatic nitrile forms via the treatment of sodium amalgam reduction or acetic anhydride, respectively. 

Nitrates have been prepared under mild conditions from chloroformates Hydroxylamines can be obtained conveniently from oximes with diborane... 

---