Hydroxylamine, condensation with

Hydroxylamine condenses with the carbonyl group of an aldehyde or ketone to form an oxime ... 

Reaction of 55a with thionyl chloride gave the 3-chloromethylene compound (55b) (62%) and with isopropyl iodide the 3-isopropoxy-methylene derivative (55c) (57%). Hydroxylamine condenses with... 

Mukund Sibi of North Dakota State University has developed (J. Am. Chem. Soc. 2004,126,718) a powerful three-component coupling, combining an a,(5-unsaturated amide 9, a hydroxylamine 10, and an aldehyde 11. The hydroxylamine condenses with the aldehyde to give the nitrone, which then adds in a dipolar sense to the unsaturated ester. The reaction proceeds with high diastereocontrol, and the absolute configuration is set by the chiral Cu catalyst. As the amide 9 can be prepared by condensation of a phosphonacetate with another aldehyde, the product 12 can be seen as the product of a four-component coupling, chirally-controlled aldol addition and Mannich condensation on a starting acetamide. 

It is assumed that hydroxylamine condenses with chloral to give oxime, which then undergoes the nucleophilic substitution with aniline, and hydrolyzes to give oximino intermediate under basic conditions. In the presence of a strong acid, such as concentrated sulfuric acid, the oximino compound cyclizes via nucleophilic addition of aromatic ring to C=N double bond. An illustrative mechanism is provided below. 

Bfflizophenone condenses with hydroxylamine hydrochloride in the presence of excess of sodium hydroxide solution to 3deld benzophenone oxime, m.p. 142° ... 

Isatin (190) is a compound with interesting chemistry. It can be iV-acetylated with acetic anhydride, iV-methylated via its sodium or potassium salt and O-methylated via its silver salt. Oxidation of isatins with hydrogen peroxide in methanolic sodium methoxide yields methyl anthranilates (81AG(E)882>. In moist air, O-methylisatin (191) forms methylisatoid (192). Isatin forms normal carbonyl derivatives (193) with ketonic reagents such as hydroxylamine and phenylhydrazine and the reactive 3-carbonyl group also undergoes aldol condensation with active methylene compounds. Isatin forms a complex derivative, isamic acid (194), with ammonia (76JCS(P1)2004). 

In general, a hydroxamic acid function results from the condensation of a hydroxylamine group with a carboxylic acid derivative. If these two groups are positioned suitably in the same molecule, spontaneous cyclization can occur. The most usual technique involves... 

In another variation of a type E synthesis, thioamides or thioureas condense with /V,/V-dimcthylacylamide dimethyl acetal to give imino compounds which react with amino-transfer reagents like hydroxylamine-O-sulfonic acid and mesitylsulfonyloxyamine (MSH) to give 3,5-substituted-l,2,4-thiadiazoles in excellent yields <1996CHEC-II(4)307>. There have been no new reports of type E syntheses since the publication of CHEC-II(1996). 

Formyl C-glycosides, prepared in three steps via the thiazole-based formy-lation of sugar lactones are readily condensed with hydroxylamine to give the corresponding oximes. The latter are the precursors of glycosyl nitrile oxides via the N-bromosuccinimide method (41). 

Oxidation of primary amines with DMD or other oxidants leads to the formation of a complex mixture of nitroso, oximes, and nitro compounds (76). Utilization of DMD in acetone affords dimethyl nitrone (22). This is likely to be a result of the initial oxidation of primary amine (19) to hydroxylamine (20) with the subsequent condensation of acetone and oxidation of imine (21) (Scheme 2.9) (77). 

Benzenesulphohydroxamic Acid.1—Hydroxylamine hydrochloride (10 g.) is boiled under reflux condenser with just enough methyl alcohol to dissolve it, and when still hot is decomposed by a solution of 3 g. of sodium in 60 c.c. of ethyl alcohol, which should not be added too quickly. After the mixture has been cooled, precipitated sodium chloride is removed at the pump and 8-5 g. of benzenesulphonyl chloride are then added in small portions to the solution of free hydroxylamine. Most of the alcohol is now removed by distillation from the water bath, the hydroxylamine hydrochloride which has separated is removed by filtration, and the filtrate is evaporated to dryness in vacuo at a moderate temperature. The residue is extracted three times with 15 c.c. portions of boiling absolute ether. Evaporation of the combined ethereal extracts in an open dish yields the benzene sulphohydroxamic acid in the form of a mass of crystalline plates which are digested with cold chloroform and filtered with suction. Yield 5-6 g. Melting point 126°. 

Starting material which, upon oxidation with PSP, gave aldehydes. These were in turn condensed with primary hydroxylamines, promoted by polymer-bound acetate, to produce nitrones. The nitrones assembled using either method then underwent 1,3-dipolar cyclo-addition reactions with various alkenes to give the corresponding isoxazolidines (Scheme 2.46 and 2.47). 

In addition to this fourfold Ugi macrocyclization using two equivalents of one bifunctionalized steroid building block and another (simpler) bifunc-tionalized building block, two different steroid building blocks can be combined to form a macrocycle in a combined Ugi 5-CR/Ugi 4-CR. For example, diacid 108 and diisonitrile 110, generated by condensation of a steroidal keto-acid with o-(carboxymethyl)-hydroxylamine, react with isobutyraldehyde and isopropylamine to form macrocycle 115 (Scheme 21). 

Various types of aromatic aldehydes with electron donating and withdrawing groups were cleanly and rapidly condensed with hydroxylamine hydrochloride at 90 °C, giving the corresponding -isomer of oximes (with OH anti to aryl) in excellent yields in the presence of CUSO4. However, aromatic ketones such as benzophenone did not afford the corresponding oximes under these conditions. 

Multicomponent reactions have recently become one of the favored methods to prepare pharmacologically important compounds. Ugi condensations with O-protected hydroxylamines have been successfully performed in THE using ZnCl2 as activating agent (Scheme 56). This synthetic strategy opens up the route to a very convergent assembly of internal hydroxamic acid derivatives (A-acyl-A-hydroxypeptides 109)" . 

In this context Miller " has demonstrated that all these issues could be overcome by hydroxamic-acids-based heteroatom activation.Therefore, S-halo or /S-hydroxy carboxylic acids 148a and 148b are converted to the corresponding hydroxamates 149a and 149b by active ester condensation with 0-substituted hydroxylamines (Scheme 69). Since chiral... 

Catalytic hydrogenation of iV-(o-nitrophenyl)aminoacetonitriles 192 with palladium(ll) oxide hydrate gives high yields of quinoxaline A -oxides 193 through condensing the reduced hydroxylamine intermediate with nitrile (Equation 31) <2001EJ0987>. 

The dibasic side chain at position 7 can be alternatively provided by a substituted amino alkyl pyrrolidine. Preparation of that diamine in chiral form starts with the extension of the ester function in pyrrolidone (46-1) by aldol condensation with ethyl acetate (46-2). Acid hydrolysis of the (3-ketoester leads to the free acid that then decarboxylates to form an acetyl group (46-3). The carbonyl group is next converted to an amine by sequential reaction with hydroxylamine to form the oxime, followed by catalytic hydrogenation. The desired isomer (46-4) is then separated... 

Isoxazole and pyrazole synthesis While 1,3-diketones undergo condensation with hydroxylamine to produce isoxazoles, with hydrazine they yield corresponding pyrazoles. 

A very flexible method of preparing unsymmetrical azo compounds makes use of the condensation of C-nitroso compounds with amines. Thionylamines have also been condensed with substituted hydroxylamines to produce azo compounds not usually accessible by other means. Treatment of dialkylsulfuric diamides with sodium hypochlorite is one means of preparing aliphatic azo compounds. Aromatic amines and aromatic nitro compounds at high temperature produce azo compounds. 

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