Pyridine oximes

Imidazo[l,2-a]pyridine , imidazo[5,l-a]isoquinoline and imidazo[2,l-a]iso-quinoline rings were successfully obtained from pyridine or isoquinoline oximes or their ethers. Thus, oxime ethers 130 were converted to imidazopyridines 131 in the presence of EtsN in methanol (equation 57). Esoquinoline oxime 132 by treatment with ethylenediaminetetraacetic acid (EDTA)/HgO and then AC2O gave imidazoisoquinoline 133 (equation 58). Similar mercury(EE)/EDTA mediated cyclization of pyridine oximes afforded fused dihydroimidazoles... 

The cadmium complexes were also investigated potentiometrically. Using this method, the complexes of cadmium with asparagine [128], taurine [129], A -(6-ami-no-3-methyl-5-nitroso-4-oxo-3,4-dihydro-pyrimidin-2-yl)glycine [130], succinate and malate [131], acetate at different temperatures [132], pyridine oxime ligands [133], 2-hydroxypropene-l,3-diamine-Af,Af,Af, A -tetraacetic acid [134] were studied. The stoichiometry and stability constants of these complexes were determined. 

Hydroxylamine hydrochloride (8) Hydroxyl amine, hydrochloride (9) (5470-11-1) 4-Acetyl pyridine oxime Ketone, methyl 4-pyridyl oxime (8) Ethanone, l-(4-pyridinyl)- oxime (9) (1194-99-6)... 

Acetyl pyridine oxime tosylate Ethanone, l-(4-pyridinyl)-0-[(4-methylphenyl)sulfonylloxime (10) (74209-52-2)... 

Syntheses, reactions, and biological activity of pyridine oximes 03KGS963. Transition metal complexes with 2,2 -bipyridines, pyridine-phosphines, and pyridine A-oxides as ligands 04IZV1733. 

Considerable work has been published on 2-pyridine oximes (16) which can be considered as imine oximes in which the imine fragment is a part of a heteroatomic ring. For example, Cu(II) complexes of (17 R = Ph or Me) have shown a subnormal magnetic moment of 1.0 BM and their EPR spectra suggest a strong coupling between the copper atoms. 

Furan-dialdehyd-(8.6)-dianil 17 1240. 2-Phenyl-5-benzoyl pyridin-oxim 21II 294. 2FhenyI-pyrldin oarbon8fture-(5)-aniIid 22 II 63. 

For water insoluble aldehydes or ketones, the following alternative procedure may be used. Reflux a mixture of 0-6 g. of the aldehyde or ketone, 0 5 g. of hydroxylamine hydrochloride, 5 ml. of ethanol and 0 5 ml. of pyridine on a water bath for 15-60 minutes. Remove the alcohol either by distillation (water bath) or by evaporation of the hot solution in a stream of air (water pump). Add 5 ml. of water to the cooled residue, cool in an ice bath and stir until the oxime crystallises Filter off the solid, wash it with a little water and dry. Recrystallise from alcohol (95 per cent, or more dilute), benzene, or benzene - light petroleum (b.p. 60-80°). 

The furo- and pyranobenzopyranones 114 and 115 are prepared by the reaction of 0-enolate of i(-keto lactone 113[132], The isoxazolc 117 is obtained by the oxidation of the oxime 116 of a, /3- or, d, 7-unsaturated ketones with PdCh and Na2C03 in dichloromethane[l 33], but the pyridine 118 is formed with PdCl2(Ph3P)2 and sodium phenoxide[134]. 

For oximes, the word oxime is placed after the name of the aldehyde or ketone. If the carbonyl group is not the principal group, use the prefix hydroxyimino-. Compounds with the group Z = N—OR are named by a prefix alkyloxyimino- as oxime O-ethers or as O-substituted oximes. Compounds with the group r C=N(0)R are named by adding A-oxide after the name of the alkylideneaminc compound. For amine oxides, add the word oxide after the name of the base, with locants. For example, C5H5N—O is named pyridine A-oxide or pyridine 1-oxide. 

A photochemical partial synthesis of aldosterone (19) made the hormone available on an industrial scale for the first time (114). Corticosterone acetate (51 acetate) is treated with nitrosyl chloride in pyridine at 20°C to yield the 11-nitrite (115). Irradiation of (115) leads to rearrangement with formation of the C g-oxime (116). Removal of the oxime residue with nitrous acid furnishes aldosterone (19) in excellent yield. 

A different type of rearrangement occurs when suitable side chains are a to a pyridine-like nitrogen atom. In the monocyclic series this can be generalized by Scheme 43. For a given side chain the rate of rearrangement is l,2,4-oxadiazoles>isoxazoles> 1,2,5-oxadiazoles. Typical side chains include hydrazone, oxime and amidine. Some examples are shown in Table 9 (79AHC(25)147). Similar rearrangements for benzazoles are discussed in Section 4.02.3.2.4. 

The sulfonate ester of o-hydroxyacetophenone oximes, when treated with pyridine, are similarly converted into a benzoxazole, but cyclize to a 1,2-benzisoxazole when treated with aqueous KOH <73JCS(P1)2220, 71T711). 

Thionyl chloride/pyridine treatment of oximes (557) is believed not to proceed via an intermediate like (558) in the generation of 1,2-benzisoxazoles, but by a chloramine intermediate (Scheme 170). A similar reaction of an A-phenylhydroxamic acid generated a benzisoxazolinone via a proposed chloramine intermediate (Scheme 170) (77AJC1847). 

WOHL - WEYGAND Aldose degradation Degradation of sugar oximes via cyanohydrins by means of an acid chloride/pyridine (Wohl) or of... 

Papaverinic acid, CieHjjO N. HjO, crystallises in small tablets, m.p. 233°. It is dibasic, readily forms an anhydride, furnishes an oxime and a phenylhydrazone, contains two methoxyl groups, and on oxidation yields veratric and pyridine-2 3 4-tricarboxylic acids, and hence is represented by the following formula —... 

Dimethyl ketals and enol ethers are stable to the conditions of oxime formation (hydroxylamine acetate or hydroxylamine hydrochloride-pyridine). Thioketals and hemithioketals are cleaved to the parent ketones by cadmium carbonate and mercuric chloride. Desulfurization of thioketals with Raney nickel leads to the corresponding methylene compounds, while thioenol ethers give the corresponding olefin. In contrast, desulfurization of hemithioketals regenerates the parent ketone. ... 

Hydroxypregna-5,16-dien-20-one Acetate Oxime 3j5-Hydroxy-pregna-5,16-dien-20-one acetate (30 g) is dissolved in 300 ml of anhydrous pyridine and 6.75 g of hydroxylamine hydrochloride is added. The mixture is stirred until solution is achieved, left in a tightly closed container at room temperature for 4 days and then poured into 1.5 liters of water. The flask is rinsed with water and the combined separated crystals are collected on a Buchner funnel, washed with water and dried to constant weight in an oven at 100°. Yield 30 g (96.5% of theory) mp 220-223°. 

Elimination of the hydroxyaminomethyl moiety from nitro oxime 15 by treatment with a diazonium salt gave hydrazone 43 (75LA1029) (Scheme 15). The same product was obtained by coupling the diazonium salt with the compound 16. On heating in aniline, oxime 15 was transformed into Schiff base 42. Acylation of the oxime 15 with benzoyl chloride in pyridine led to a mixture of furazan 44 and dinitrile 45. 

Preparation and use of amphiphilic oximes, derivatives of pyridine, pyridazine, pyrimidine, and pyrazine 98CFY469. 

Reductive alkylations have been carried out successfully with compounds that are not carbonyls or amines, but which are transformed during the hydrogenation to suitable functions. Azides, azo, hydrazo, nitro and nitroso compounds, oximes, pyridines, and hydroxylamines serve as amines phenols, acetals, ketals, or hydrazones serve as carbonyls 6,7,8,9,12,17,24,41,42,58). Alkylations using masked functions have been successful at times when use of unmasked functions have failed (2). In a synthesis leading to methoxatin, a key... 

Excellent yields of the oximes of phenylacetaldehydes are obtained by reduction of 6-nitrostyrenes over Pd-on-C in a pyridine solvent (74,75). The technique gives yields of only about 60% when applied to aliphatic unsaturated nitrocompounds better yields are obtained in acidic media(6 5). Over 5% Rh-on-Al203 in ethanol-acetic acid-ethyl acetate, 2- 6-dinitro-styrenes are converted to 2-nitrophenylacetaldehyde oximes (13). 

A mixture of 202 g 2-amino-5-chlorobenzophenone, 190 g hydroxylamine hydrochloride, 500 cc pyridine and 1,200 cc alcohol was refluxed for 16 hours, then concentrated in vacuc to dryness. The residue was treated with a mixture of ether and water. The water was separated, the ether layer containing a considerable amount of precipitated reaction product was washed with some water and diluted with petroleum ether. The crystalline reaction product, 2-amino-5-chlorobenzophenone-0 -oxime, was filtered off. The product was recrystallized from a mixture of ether and petroleum ether forming colorless prisms, MP 164° to 167°C. 

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