Hydroxylamine unsubstituted

Amination at an azole ring nitrogen is known for Af-unsubstituted azoles. Thus 4,5-diphenyl-1,2,3-triazole with hydroxylamine-O-sulfonic acid gives approximately equal amounts of the 1- (104) and 2-amino derivatives (105) (74AHC(16)33). Pyrazole affords (106) and indazole gives comparable amounts of the 1- and 2-amino derivatives. 

Two substituents on two N atoms increase the number of diaziridine structures as compared with oxaziridines, while some limitations as to the nature of substituents on N and C decrease it. Favored starting materials are formaldehyde, aliphatic aldehydes and ketones, together with ammonia and simple aliphatic amines. Aromatic amines do not react. Suitable aminating agents are chloramine, N-chloroalkylamines, hydroxylamine-O-sulfonic acid and their simple alkyl derivatives, but also oxaziridines unsubstituted at nitrogen. Combination of a carbonyl compound, an amine and an aminating agent leads to the standard procedures of diaziridine synthesis. 

The condensation of P-keto esters with hydroxylamine can occur in two directions to give either isoxazolin-3-ones [which exist predominately as 3-hydroxyisoxazoles (2)] or isoxazolin-5-ones (3). Early work by Claisen, Hantzch, and others showed that the products from 2-unsubstituted P-keto esters were isoxazolin-5-ones. In the early 1960 s, Katritzky found that 2-substituted analogues give 3-hydroxyisozaoles. Jacquier later showed that both types of products could be produced from both types of keto esters depending on the precise pH variation during the reaction workup. ... 

Unsubstituted quinazoline 3-oxide was prepared in an attempt to react quinazoline with hydroxylamine. This reaction gave a product of variable composition, but when an acetone solution was heated in a sealed tube it gave quinazoline 3-oxide. The oxide is more conveniently prepared, in excellent yield, from o-aminobenzaldehyde oxime and ethyl orthoformate. This method appears to be of general use and has been used for the preparation of 4-methylquinazoline... 

A number of recent papers have described the use of new types of /3-diketone derivatives to synthesize isoxazoles. We must first mention 1,1,3,3-tetraalkoxypropanes which are now manufactured on a large scale. Condensation of these derivatives with hydroxylamine has made readily available the parent compound, unsubstituted isoxazole itself (4). " This type of reaction using tetraalkoxypropane... 

Unsubstituted hydroxylamines ( NOH) which may be formed in reactions 6 and 8 are powerful antioxidants, both by peroxyl radical scavenging and by hydroperoxide decompositions. 

An unsubstituted hydroxylamine is a powerful hydroperoxide decomposer and peroxyl radical scavenger, and could play an important role in photo-stabilization even if present at only a low concentration after dark intervals. 

After 30 min at 120°C under vacuum, an equimolar mixture with the cone, acid exploded violently. Salts of unsubstituted hydroxylamine are thermally unstable. 

Another synthetic approach for generating sugar-containing nitrones is by initial treatment of sugars with unsubstituted hydroxylamine. The resulting cyclic hydroxylamine of the tautomeric mixture (68a) and of the open chain oxime (68b) react with aldehydes to give the corresponding nitrones (69) (Scheme 2.24) (216-220). 

Enantio-pure five-membered cyclic nitrones (154) and (155) were formed in a one-pot synthesis from the corresponding lactols (152) and (153) as the result of their reactions with unsubstituted hydroxylamine and by (a) subsequent treatment with MsCl and NaOH (Scheme 2.55) (310a) or by (b) subsequent treatment with TBDMSC1,12, TPP, imidazole, and tetrabutylammonium fluoride (TBAF) (310b). 

Due to the restricted availability of nitroso components, it more convenient to prepare acylnitroso compounds in situ from iV-acyl or Af-carbamoyl hydroxylamines with NaI04 (equation 100) . Subsequent deprotection results in an Af-unsubstituted dihydro-1,2-oxazine cycle. The reaction is also commonly employed for intramolecular cyclo-additions ". ... 

Another approach toward Af-unsubstituted dihydro-1,2-oxazines involves cycloaddition of easily available a-chloro nitrosoalkanes 155 to 1,3-dienes (e.g. 156, equation 101). Subsequent alcoholysis results in the removal of the alkyl function and provides N-unsubstituted cyclic hydroxylamines of type 157 (equation 101) ... 

Cycloaddition of enantiomerically pure a-chloro nitroso compounds derived from steroids and carbohydrates (e.g. 158, equation 102) proceeds with considerable stereoselectivity. Final removal of the chiral auxiliary results in Af-unsubstituted cyclic hydroxylamines of high ee. 

Oxaziridines unsubstituted at nitrogen (9, R =H) (in general used as aminating reagents, see Sections 3.5.4 and 3.5.6), are prepared by treatment of carbonyl compounds with chloramine or hydroxylamine-O-sulfonic acid in aqueous media (91S327). This method is, however, limited to certain carbonyl compounds with cyclohexanone, followed by butanone, benzaldehyde, and trichloroacetaldehyde giving the best results. 

Mesoionic pyrido[2,l- >][1,3]oxazines (54) afforded 4-oxo-4//-pyrido[l,2-a]pyrimidin-l-iumolates (55) and 4//-quinolizin-4-one (56) with phenyl iso(thio)cyanates [78LA1655 79CB1585 82ZN(B)222] and dimethyl acetylenedicarboxylate (79CB1585), respectively. Reaction of 2-cyano-3-methyl-lH,6//-pyridol[l,2-a][3,l]benzoxazine-l,6-dione with ammonium acetate and hydroxylamine, hydrazines, primary aliphatic or aromatic amines, and (thio)ureas gave 5-unsubstituted and 5-substituted 2-cyano-3-methyl-l//,6H-pyrido[l,2-a]quinazoline-l,6-diones (93CCC1953). 

Another synthetic method for the preparation of aziridinyl ketones involves the initial modification of unsaturated ketones, with formation of /3-methoxyamino derivatives, followed by treatment with either metal alcoholates [11, 28, 29, 30, 31], or hydroxylamine hydrochloride and then potassium hydroxide [32]. An obvious drawback of this approach is the possibility of obtaining an exclusively unsubstituted nitrogen atom for the aziridinyl ketones. Among the advantages are high yields for these reactions. For example, Jin et al. [31] recorded yields of aziridine 18 of 99%. In other publications the yields of target compounds were reported to be around 90%. 

Coordination of vanadate by hydroxylamines is similar in many respects to coordination by hydrogen peroxide. Various hydroxylamine complexes are known, although only detailed studies of the aqueous chemistry have been carried out with hydroxylamine and its A -melhyl and A,A-dimcthyl derivatives. -substitution apparently has only a small influence on product formation. There is, however, scope for a wider range of isomeric forms with the A-methylated ligand compared to the unsubstituted and dimethylated ligands, and a number of isomers have been observed... 

Reaction of open-chain and cyclic aminomethylenediones with hydroxylamine yields the correspondingly substituted 4-acylisoxazoles. Cyclopentanedione derivatives lead to simple non-cyclized product by substitution of the amine. The 3-unsubstituted isoxazoles easily isomerize to the corresponding 2-cyano-l,3-diones283 (equation 209). 

Compounds of this type are regarded as 4,5-disubstituted isoxazoles, and as such they react. Their formation from 2-acylcyclohexanones and hydroxylamine is a special case of the general method of isoxazole formation from /9-diketones. 2-Formyl (hydroxymethylene) cyclohexanones, obtained from the respective cyclohexanones and ethyl formate, give 3-unsubstituted derivatives [Eq. (7)].84-91 This reaction has been applied to a stereospecific synthesis of estrone.87,89... 

Methylanthranil is much more stable towards bases than the unsubstituted compound. However, prolonged heating with sodium hydroxide was reported to form 2-aminoacetophenone,250 and the action of hydroxylamine on a derivative produced a mixture of the corresponding aminoacetophenone and its oxime.125... 

Secondary amines give only a monosubstituted product. Both of these reactions are thermally reversible. The product with ammonia (3,3, 3"-nitrilotrispropionamide [2664-61-1] C9HlgN403) (5) is frequently found in crystalline acrylamide as a minor impurity and affects the free-radical polymerization. An extensive study (8) has determined the structural requirements of the amines to form thermally reversible products. Unsymmetrical dialkyl hydrazines add through the unsubstituted nitrogen in basic medium and through the substituted nitrogen in acidic medium (9)). AlonoalkyHiydroxylamine hydrochlorides react with preservation of the hydroxylamine structure (10). Primary nitramines combine in such a way as to keep the nitramine structure intact. 

The unsubstituted hydroxylamine 10 (X = OH) does not react analogously, and the amino derivative 10 (X = H) is unreactive. The most important experimental variable is the anode material the results reported in the table were obtained by using a vitrious carbon anode, but the yield of the products 11 was increased by working with a graphite felt anode, whereas no product was obtained using platinum foil. 

The same methodology was employed by Tiecco to effect the cyclizations of 0-allyl oximes 164 indicated in Scheme 25. Treatment of the intermediate iminium salt 165 with sodium borohydride affords M-alkyl isoxazolidines 166 [95]. Alternatively, 165 can be treated with water to produce M-unsubstituted isoxazolidines 167 [96]. This synthesis of M-alkyl isoxazolidines represents a valid alternative to that described in Scheme 23. Moreover, the present cyclization reaction is much more stereoselective than the cyclization of 0-allyl hydro-xylamines. In fact, when the methyl derivative 168 was employed, the two isomeric isoxazolidines 153 and 154 were obtained in a ratio of 95 5. The same two products were, in contrast, formed in a 1 1 ratio when the reaction was carried out starting from the corresponding 0-allyl hydroxylamines. Clearly, the steric requirements for the selenium-induced cyclization of the 0-allyl oximes are much greater than those for the corresponding 0-allyl hydroxylamines. 

Unsubstituted aliphatic monoximes can be produced by-treatment of an aldehyde or ketone in aqueous or alcoholic media with Crismer s salt, [Zn(NH20H)2Cl2]. The thermal decomposition of Crismer s salt in vacuo has been used to prepare pure hydroxylamine. The following procedure, a rapid preparation producing a high yield of this complex, is a modification of a method first used by Crismer. ... 

The hydrazine (340) and acetic anhydride give the pyrazolopyrimidine (341 R = Me). With mixed formic-acetic anhydride the unsubstituted derivative (341 R = H) is obtained (58LA(615)42). The pyridylacetic ester (342) reacts with hydroxylamine-O-sulfonic acid in water at room temperature to give the phenolic compound (13) (see Section 4.05.2.4) (76BCJ1980). 

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