3-Alkoxy-5-hydroxy

EthoxycarbonyI-l-hetaryl-thioharnstoffe183 oder N-Ethoxycarbonyl-thiocarbamidsaure-ester184 344 reagieren mit freiem Hydroxylamin in Ethanol zu den entsprechend substituierten 3-Amino-5-hydroxy- bzw. 3-Alkoxy-5-hydroxy-l, 2,4-oxadiazolen z.B. ... 

Alkoxy-5-hydroxy- bzw. 3-Aryloxy-5-hydroxy-l,2,4-oxadiazole allgemeine Arbeitsvorschrift ... 

Malonsaure-ester-nitrile sind Edukte fur die Herstellung von 3-Amino-5-hydroxy- oder 3-Alkoxy-5-hydroxy-l H-pyrazolen. Zumeist wird dabei Malonsaure-ethylester-nitril zu-nachst zu 3-Ethoxy-3-imino-propansaure-ethylester umgesetzt (Pinner-Reaktion)424 426, der dann z. B. mit einem Aryl-hydrazin iiber die isolierbare Zwischenstufe eines 3-Arylhydr-azino-3-imino-propansaure-esters bei Basen-Einwirkung (z. B. Alkanolat) cyclisiert. In einigen Fallen ist es zweckmaBig, die Zwischenstufe zu isolieren und in einer zweiten Stufe zu cyclisieren. 

In 3-Alkoxy-5-hydroxy-lH-pyrazolen laBt sich der Alkoxy-Rest durch Erhitzen mit Ami-nen1937,1937a 1947 und Hydrazin396 substituieren. 

In Analogic zum Austausch der 3-Alkoxy-Gruppe in 3-Alkoxy-5-hydroxy-lH-pyrazolen (s.S. 641) durch Stickstoff-Basen laBt sich die Mercapto-Gruppe substituieren1344. 

Oxygen-centered radicals are arguably the most common of initiator-derived species generated during initiation of polymerization and many studies have dealt with these species. The class includes alkoxy, hydroxy and aeyloxy radicals and tire sulfate radical anion (formed as primary radicals by homolysis of peroxides or hyponitrites) and alkylperoxy radicals (produced by the interaction of carbon-centered radicals with molecular oxygen or by the induced decomposition of hydroperoxides). 

Several studies, however, conclusively showed that the intensity of the sweet taste depends strongly upon the number of hydroxyl groups in the A-ring. - - For example, compound 85 and its sodium salt, which have only one hydroxyl group in the A-ring, are less sweet than the 2,6-dihydroxy compound. Furthermore, there is also a requirement for an orrto-hydroxy ketone system in ring A, as compound 86 is tasteless, and because it had already been shown that the alkoxy-hydroxy substituents on ring B are also... 

IR Isoprene rubber poly (els-1,4-isoprene) PEO Poly(ethylene oxide) a-Alkoxy- >-hydroxy polyethylene oxide... 

Alkoxy(hydroxy)thiazolidine-2)4-diones have been prepared by the reaction between two imidazolides [121] °... 

Substituents with lone electron pairs, such as alkoxy, hydroxy, alkyl, and aryl-amino groups, are known as electron donors. The CH3 group, despite the absence of such free electron pairs, is also considered an electron donor. Functional groups with conjugated rr-electron systems, such as NOz, COOH, COOR, SOz, or SOzAr act as electron acceptors. 

SCHEME 13. Synthesis of a-alkoxy hydroxy hydroperoxides by ozonolysis, OMe OOH... 

As described in Section III, practically all known conversions of 2-benzopyrylium salts are the result of their reactions with nucleophiles, and 2-benzopyrylium, similar to its monocyclic analog [82AHC(Suppl)], behaves chemically more like a carbenium ion, and not like an oxonium salt. This fact can be easily understood if one takes into account resonance formulas a-f, where an oxonium form f is added for the presence of an alkoxy (hydroxy) substituent in position 6. 

Deoxygenation of a-alkoxy(hydroxy) esters. This deoxygenation can be effected by SmI2-HMPA in THF with an alcohol as the proton source. The reaction is... 

It is known that the halogen or OTf ligand on R-Pd-X (1) is readily displaced by an alkoxy, hydroxy, or acetoxy anion to provide a basic R-Pd-OR" (4) complex, as is seen in the syntheses of 6 and 7. Thus, available information indicates that there are two transmetalation processes (path A and path B) for the crosscoupling reaction in alkaline solution however, it is not yet obvious in many reactions which process is predominant. It was recently demonstrated that the reaction of 9-alkyl-9-BBN (10) proceeded through the former process (path A) and the latter (path B) was predominant in a less acidic 9-oxa-lO-borabicy-clo[3.3.2]decane (14) [23] (Scheme 3).NMR study revealed the exclusive formation of an ate-complex (11) between 10 and NaOH whereas the corresponding 14 remained unchanged with an added base. The reactions were zero-order in... 

Rieii and co-worker have condenaed Beveral aliphatic alcohols Trith alkyl glycidyl aulddea, thereby eecvnng the Alkoxy- -hydroxy-propylaulhdca shown in q. (6d3). 

Hydrogenolysis using lithium aluminum hydride under reflux without any additives requires the presence of strongly electron-donating groups such as alkoxy, hydroxy, and amino groups at the ortho or para position to the carbonyl substituent in the aromatic system (equation 13). ... 

A. Repbcement of Halogeno Substituents by Alkoxy, Hydroxy, and Alkylthio Groups... 

Tetrachlorocyclopropene in the presence of Lewis acids or the trichlorocyclopropenyl cation are important starting materials in cyclopropenone syntheses In this method the cyclopropene or salt is reacted with benzene or derivatives of benzene bearing functional groups such as alkyl, alkoxy, hydroxy, or halogen to yield diaryl-substituted cations. Upon hydrolysis these cations yield the cyclopropenone. In some cases the monoaryl cation (32) can be obtained and converted to the aryl chlorocyclopropenone 33. Alternatively, the monoaryl cation can be reacted with a second aromatic species to give cyclopropenones with different aryl groups (equation 30). 

It is known that the halogen ligand on an organopalladium(II) halide is readily displaced by an alkoxy, hydroxy, or acetoxy anion to provide the reactive Pd-OR complexes 20 [58], which have been postulated as reaction intermediates [59] or isolated [55, 56] from the reaction of organopalladium(II) halides with sodium hydroxide or methoxide. It is not yet obvious, in many reactions, which process shown in Scheme 2-18 or 2-23 is predominant however, the formation of alkoxo-, hydroxo- or acetoxopalladium(II) intermediates should be considered to be one of the crucial transmetallation processes in base/palladium-induced cross-coupling reactions. 

Iranpoor, N., Shekarriz, M. Regioselective 1,2-alkoxy, hydroxy, and acetoxy iodination of alkenes with I2catalyzed by Ce(S03CF3)4. Tetrahedron 2000, 56, 5209-5211. 

The electrolysis products of different carboxylates have been compared with the ionization potentials of the intermediate radicals. From this it appeared that alkyl radicals with gas-phase ionization potentials smaller than 8 eV mainly lead to carbenium ions. Accordingly, a-substituents such as carboxy, cyano or hydrogen support the radical pathway, whilst alkyl, cycloalkyl, chloro, bromo, amino, alkoxy, hydroxy, acyloxy or aryl more or less favor the route to carbenium ions. Besides electronic effects, the oxidation seems also to be influenced by steric factors. Bulky substituents diminish the extent of coupling. The main experimental factors that affect the yield in the Kolbe electrolysis are the current density, the pH of the electrolyte, ionic additives, the solvent and the anode material. 

Z = H, halo, C1-C20 alkyl, cycloalkyl, lower alkoxy, cyano R = Cj-C25 alkyl, cycloalkyl or halo-lower alkyl, fluoro-lower alkyl, aryl, lower alkoxy, hydroxy, carboxy, lower-alkyl carbonyl or lower alkoxy-carbonylo3Qr or (CRiR2)p-(CR3=CR4) j Q or (CRiR2)p-... 

The efficient decomposition of hydroperoxides by a non-radical pathway can greatly increase the stabilizing efficiency of a chain-breaking antioxidant. This generally occurs by an ionic reaction mechanism. Typical additives are sulfur compounds and phosphite esters. These are able to compete with the decomposition reactions (either unimolecular or bimolecular) that produce the reactive alkoxy, hydroxy and peroxy radicals and reduce the peroxide to the alcohol. This is shown in the first reaction in Scheme 1.69 for the behaviour of a triaryl phosphite, P(OAr)3 in reducing ROOH to ROH while itself being oxidized to the phosphate. 

Bei blockierter 4-Stellung erhalt man Salicylaldehyde. Von besonderem Interesse ist die Mehrfachformylierung von Dihydroxy- und Alkoxy-hydroxy-arenen95. 

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