Oximes catalytic reduction

Reduction of unsaturated oximes without effect on the C=C double bond is best carried out by sodium amalgam at not too high a temperature. Quinone dioximes are best converted into the amines by use of sodium sulfide in boiling alcohol.115 Amino carboxylic acids are prepared from the corresponding oxo carboxylic acid oximes, catalytic reduction being in these cases the method of choice. 

Ivermectin is the catalytic reduction product of avermectin, a macroHde containing a spiroketal ring system. Two other related antibiotics having significantly different stmctural features and biological properties, moxidectin and milbemycin oxime, were more recentiy introduced into the market. Although these compounds have no antimicrobial activity, they are sometimes referred to as antibiotics because they are derived from fermentation products and have very selective toxicities. They have potent activity against worms or helminths and certain ectoparasites such as mites and ticks. 

The catalytic reduction of 2-methyl-3-phenyl-3-isoxazoline (159) produced /3-hydroxypropiophenone (160) (74CPB70). Ring fission also occurred on base treatment of the 3,5-diaryl-3-isoxazoline (161) to give the a,/3-unsaturated oxime (162) (70CI(L)624). 

Catalytic reduction of fluormated aliphatic and aromatic nitro compounds to give oximes and amines was described previously, as was the use of dissolving metals to prepare amines [Si] Refmement of these techniques has resulted in optimized yields and, as indicated in equations 69 and 70, in selective reductions [S6, 87]... 

Asymmetric catalytic reduction reactions represent one of the most efficient and convenient methods to prepare a wide range of enantiomerically pure compounds (i.e. a-amino acids can be prepared from a-enamides, alcohols from ketones and amines from oximes or imines). The chirality transfer can be accomplished by different types of chiral catalysts metallic catalysts are very efficient for the hydrogenation of olefins, some ketones and oximes, while nonmetallic catalysts provide a complementary method for ketone and oxime hydrogenation. 

Intermolecular coupling between ketones and 0-methyl oximes, hydrazones and nitrones is achieved on reduction at a tin cathode in isopropanol [105]. It is not clear which of the reacting species accepts the initial electron in these processes. The reaction with 0-methyloximes, followed by catalytic reduction of the first formed O-methylhydroxylamine, is a convenient synthetic route to 2-amino-alcohols. 

The preparation of oximes from olefins is a valuable approach for the synthesis of nitrogen-containing compounds such as amino acids and heterocycles. Okamoto and colleagues have reported that a catalytic reduction-nitrosation of styrenes 31 with ethyl nitrite and tetrahydroborate anion by the use of bis(dimethylglyoximato)cobalt(II) complex afford the corresponding acetophenone oximes 32 (Scheme 23). 

Isoxazoles have been used to transpose functionality within a,/3-unsaturated carbonyl compounds (72JA9128). Thus, on exposing either (E)- or (Z)-/3-ionone oxime (449) to a mixture of iodine-potassium iodide in hot aqueous THF containing sodium bicarbonate, the isoxazole (450) was formed in high yield. Catalytic reduction of this isoxazole led... 

Catalytic Reduction of Oximes— Oximes may be reduced to primary amines in good yield by hydrogen in presence of nickel-kielselguhr (p. 172). (Am. Soc., 55, 1669). 

Enantioselective reduction of oxime ethers promoted by chiral spiroborate esters (10) with an O3BN framework is reported. In the presence of (R,S)-10, aralkyloxime ethers are reduced by borane-THF at give (S)-l-aralkylamine in high yield and excellent enatiomeric excess (up to 98% ee). A possible mechanism (Scheme 13) of the catalytic reduction is suggested.310... 

Oximes can be converted electrochemieally to the corresponding amino compounds in a smooth reaction. However, apart from a few examples, the electrosyntheses are inferior to catalytic reductions, so that only a few examples are described in the patent literature. 

Only limited success has been reported in the reduction of ketimines due to the low electrophilicity of the imine carbon and the rapid equilibration between the (E)- and (Z)-isomers. However, high enantioselectivity was achieved in catalytic reduction of imines of keto esters (Equation (261))1125 and oximes of acetophenone (Equation (262))1089,1125-1131 cyclic ketones (Equation (263)),1127 and a ketone possessing a boryl group (Equation (264)).1128... 

Primary Amines Primary amines result from condensation of hydroxylamine (zero alkyl groups) with a ketone or an aldehyde, followed by reduction of the oxime. Hydroxylamine is used in place of ammonia because most oximes are stable, easily isolated compounds. The oxime is reduced using catalytic reduction, lithium aluminum hydride, or zinc and HC1. 

Catalytic reduction of 1,2,4-oxadiazoles also breaks the NO bond e.g., 385 gives 386. Benzofuroxan can be reduced under various conditions to benzofurazan 387, the bis-oxime 388, or o-phenylenediamine. Reduction using copper and hydrochloric acid produces o-nitroanilines (Scheme 77). 

D. The use of chiral oxazaborolidines as enantioselective catalysts for the reduction of prochiral ketones, imines, and oximes, the reduction of 2-pyranones to afford chiral biaryls, the addition of diethylzinc to aldehydes, the asymmetric hydroboration, the Diels-Alder reaction, and the aldol reaction has recently been reviewed.15b d The yield and enantioselectivity of reductions using stoichiometric or catalytic amounts of the oxazaborolidine-borane complex are equal to or greater than those obtained using the free oxazaborolidine.13 The above procedure demonstrates the catalytic use of the oxazaborolidine-borane complex for the enantioselective reduction of 1-indanone. The enantiomeric purity of the crude product is 97.8%. A... 

Various studies have been devoted to the synthesis of amino-substituted steroids. These compounds can be prepared either from an alcohol, by displacement of a toluene-p-sulphonyl group by an amine, ° from a ketone, either by reduction of the corresponding oxime ° ° or by Beckmann rearrangement of 20-keto-oximes, ° or by catalytic reduction of a nitro-group. ° Another... 

Reduction, nitrogen protection, and oxidation then gave the keto-derivative (449), which was cyclized to (450). Finally, the 3/ -amino-group in (451) was introduced by catalytic reduction of the oxime. ... 

Dimethylaniline has been prepared by reduction of the corresponding nitro compound, either chemically or catalyti-cally. It has been prepared from 3,4-dimethylphenol by heating with ammonia, ammonium bromide, and zinc bromide from w-toluidine hydrochloride by alkylation with methanol at high temperatures from anhydro-4-amino-2-methylbenzyl alcohol by dry distillation from calcium hydroxide from 2-methyl-S-aminobenzyl alcohol by reduction with sodium from 2-methyl-5-nitrobenzyl chloride and 2-methyl-S-nitrobenzyl acetate by catalytic reduction from o-xylene by direct amination with hy-droxylamine hydrochloride in the presence of aluminum chloride and from 3,4-dimethylacetophenone by the Beckmann rearrangement of the oxime.i" The present method has been published. ... 

Bradsher and co-workers have developed a general method for synthesizing the protoberberine ring system. It involves the condensation of a properly constituted 1-isoquinoline carboxaldehyde with the appropriately substituted benzyl bromide. Acid-catalyzed cyclization of the resulting quaternary salts affords the fully aromatic tetracyclic ring system which on catalytic reduction leads directly to the tetrahydro-protoberberine skeleton. Recent modifications 93) of this synthetic method involving the use of the oxime, or better, the ethylene acetal of the 1-isoquinoline carboxaldehyde, have permitted the use of less vigorous conditions for the production of the tetracyclic intermediate... 

Dihydrodesoxycodeine-D [xm], the only non-phenolic dihydro-desoxycodeine, can be prepared by the catalytic hydrogenation of a-chlorocodide [rv] [29], /3-chlorocodide [v, It = Cl] [7, 29], bromocodide [v, R = Br] [29], and desoxycodeine-C [ix] hydrochloride [6], It has also been reported to be formed by catalytic reduction of codeinone oxime [xlii] hydrochloride [30]. Dihydrodesoxycodeine-D methine [xlhi] results from Hofmann degradation of the methiodide [7], and a substance that is presumably the dihydromethine [xliv] is obtained by catalytic reduction of a-chlorocodeimethine [xlv] [26]. 

Dihydrothebainone [ix], obtained by the catalytic reduction of thebainone-A [v] [1] and thebainone-B [xm] [13], can be most conveniently prepared by the catalytic reduction of thebaine in acid solution [9-12, 25], and it can also be obtained by the hydrolysis of its two enol ethers (see below). It is a phenolic, ketonic, base, that shows the diazo-reaction in dilutions up to 1 in 2,000,000 [26-27], gives a methyl ether [28], oxime [9], semicarbazone [29], and a benzylidene [30] and piperonylidene [25] derivative. The optical antipode is produced by the sodium amalgam reduction of sinomenine [xxvi] and is known as desmethoxydihydrosinomenine [31]. 

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