Oximes development

An example of the usefulness of the methodology was the new industrial route to cyclohexanone oxime developed by Corma and Serna, a process which is based on the selective hydrogenation of 1-nitro-l -cyclohexene by gold nanoparticles supported on Ti02 or Fe203 [220]. 

Application as a Component of an Asymmetric Catalyst. Amino alcohol (1) has proven to be a highly versatile ligand for use in asymmetric catalysts for a series of reactions. One of the most comprehensively studied uses is as an ox-azaborolidine derivative such as 8 for the asymmetric control of the reduction of ketones by borane. Although its use was first described with stoichiometric levels of 1 being employed for the reduction of both ketones and oximes, development of the system has delivered a catalytic method requiring only 5-10 mol % catalyst. Enantiomeric excesses of over 85% and as high as 96% have been achieved for a range... 

LIX 63, an aliphatic a-hydroxyoxime, was the first commercial reagent developed for copper. Although it was very selective for copper, it operated at pH values of 5 to 8. Since most leach solutions have pH values between 0.7 and 2.2, it was necessary to optimise the pH dependence of the extractants for use under more acidic conditions. The first reagent used in a full-scale plant was LIX 64N, a P-hydroxybenzophe-none oxime developed by General Mills (now Cognis) and comprising a mixture of LIX 63 (2% by mass) and LIX 65N (40%) (Arbiter and Fletcher 1994 House 1985 Dasher and Power 1971). 

An alternative route to cyclohexanone oxime developed in Italy by Enichem is shown in the following reaction. Cyclohexanone oxime is produced by the ammoxidation of cyclohexanone with ammonia and aqueous hydrogen peroxide in the presence of a solid, recyclable catalyst, titanium silicalite (TS-1). This reaction step eliminates approximately one-third of total salt formation. However, the oxime is still converted to caprolactam through the conventional route (Beckmann rearrangement), catalyzed by stoichiometric amounts of sulfuric acid, and produces ammonium sulfate salt. Therefore, this alternative process still leaves something to be desired. 

The condensation reaction between free hemiacetals and N,0-alkyl or aryl glycosyl oximes developed by Dumy and coworkers allows the diastereoselective derivation... 

I h c simplest approximation to tlic Scfi rod in gcr equation is an in clepen dcri l-eleelron appi oxim alion, sucli as Ui e H iiekel method for tr-clcetron systems, developed by H. Huckel. I-atcr, others, principally Roald Hoffmann of Cornell University, extended tlie Htiekel approximations to arbitrary systems having both nand a electrons the Hxtended Huckel Theory (KHT) approximation. ... 

In a 250 ml. conical flask mix a solution of 14 g. of sodium hydroxide in 40 ml. of water and 21 g. (20 ml.) of pure benzaldehyde (Section IV,115). Add 15 g. of hydroxylamine hydrochloride in small portions, and shake the mixture continually (mechanical stirring may be employed with advantage). Some heat is developed and the benzaldehyde eventually disappears. Upon coohiig, a crystalline mass of the sodium derivative separates out. Add sufficient water to form a clear solution, and pass carbon dioxide into the solution until saturated. A colourless emulsion of the a or syn-aldoxime separates. Extract the oxime with ether, dry the extract over anhydrous magnesium or sodium sulphate, and remove the ether on a water bath. Distil the residue under diminished pressure (Fig. 11,20, 1). Collect the pure syn-benzaldoxime (a-benzald-oxime) at 122-124°/12 mm. this gradually solidifies on cooling in ice and melts at 35°. The yield is 12 g. 

Developments in aliphatic isocyanates include the synthesis of polymeric aliphatic isocyanates and masked or blocked diisocyanates for appflcafions in which volatility or reactivity ate of concern. Polymeric aliphatic isocyanates ate made by copolymerizing methacrylic acid derivatives, such as 2-isocyanatoethyl methacrylate, and styrene [100-42-5] (100). Blocked isocyanates ate prepared via the reaction of the isocyanate with an active hydrogen compound, such as S-caprolactam, phenol [108-95-2] or acetone oxime. 

The products have the characteristic lemon odor of citral and also have greater odor strength and chemical stabiUty than citral. As the need for more stable citms-like fragrances for use in bleach developed, other nitrile compounds have been made available commercially. CitroneUyl nitrile is made from citroneUal dimethyloctanenitrile is produced from dimethyloctanal by the oximation method. 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

This method was developed because conventional procedures failed to cleave the oxime. 

The present procedure was developed from those of Wallach and Freylon, based upon the general method discovered by Leuckart. a-Phenylethylamine also can be prepared satisfactorily by the reduction of acetophenone oxime with sodium and absolute alcohol or sodium amalgam, but the reagents are more expensive and the processes less convenient. The amine has been obtained by reducing acetophenone oxime electro-lytically, by reducing acetophenone phenylhydrazone with sodium amalgam and acetic acid, from a-phenylethyl bromide and hexamethylenetetramine, and by the action of methyl-magnesium iodide upon hydrobenzamide, as well as by other methods of no preparative value. 

Caprolactam is preferred to w-aminocaproic acid for the manufacture of nylon 6 because it is easier to make and to purify. Over the years many routes for the manufacture of caprolactam itself have been developed and major commercial routes are summarised in Figure 18.6. Of these routes the bulk of manufacture is via cyclohexanone and cyclohexanone oxime. 

NaN02, 1 N HCl, CH3OH, H2O, 0°, 3 h, 76% yield. In the last step of a synthesis of erythronolide A, acid-catalyzed hydrolysis of an acetonide failed because the carbonyl-containing precursor was unstable to acidic hydrolysis (3% MeOH, HCl, 0°, 30 min, conditions developed for the synthesis of erythronolide B). Consequently, the carbonyl group was protected as an oxime, the acetonide was cleaved, and the carbonyl group was regenerated. 

A process for the preparation of pyrimidine A-oxides from carboxamide oximes has been developed (98T4387). Direct oxidation of pyrimidines is inconvenient for the preparation of nonsymmetric substituted pyrimidines because it gives a mixture of oxidation products ( -N- and 3-A-oxides). Methoxybutenone with carboxamide oximes regioselectively forms A-oxides of pyrimidines 281, which indicates... 

Various convenient methods for the oxidadon of oximes to nitro compounds have beo) developed in recent years. Olah has reported a convenient oxidadon of oximes to nitro compounds v/ith soditun perborate in glaciid acedc acid fEq. 2.60. ... 

Bamberger s main achievements were the rediscovery of Blomstrand s diazonium formula and the development of a large number of methods for the preparation of diazoates and azo compounds. In the end, Bamberger abandoned his negative attitude towards the stereoisomerism of the diazoates by reason of his own experiments, which demonstrated the similarities in the oxidation behavior of isomeric series of oximes and diazo compounds (Bamberger and Baudisch, 1912). 

Catalytic asymmetric hydrogenation is a relatively developed process compared to other asymmetric processes practised today. Efforts in this direction have already been made. The first report in this respect is the use of Pd on natural silk for hydrogenating oximes and oxazolones with optical yields of about 36%. Izumi and Sachtler have shown that a Ni catalyst modified with (i ,.R)-tartaric acid can be used for the hydrogenation of methylacetoacetate to methyl-3-hydroxybutyrate. The group of Orito in Japan (1979) and Blaser and co-workers at Ciba-Geigy (1988) have reported the use of a cinchona alkaloid modified Pt/AlaO.i catalyst for the enantioselective hydrogenation of a-keto-esters such as methylpyruvate and ethylpyruvate to optically active (/f)-methylacetate and (7 )-ethylacetate. 

Clerici and Porta reported that phenyl, acetyl and methyl radicals add to the Ca atom of the iminium ion, PhN+Me=CHMe, formed in situ by the titanium-catalyzed condensation of /V-methylanilinc with acetaldehyde to give PhNMeCHMePh, PhNMeCHMeAc, and PhNMeCHMe2 in 80% overall yield.83 Recently, Miyabe and co-workers studied the addition of various alkyl radicals to imine derivatives. Alkyl radicals generated from alkyl iodide and triethylborane were added to imine derivatives such as oxime ethers, hydrazones, and nitrones in an aqueous medium.84 The reaction also proceeds on solid support.85 A-sulfonylimines are also effective under such reaction conditions.86 Indium is also effective as the mediator (Eq. 11.49).87 A tandem radical addition-cyclization reaction of oxime ether and hydrazone was also developed (Eq. 11.50).88 Li and co-workers reported the synthesis of a-amino acid derivatives and amines via the addition of simple alkyl halides to imines and enamides mediated by zinc in water (Eq. 11.51).89 The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated products with good diastereoselectivities that can be converted into enantiomerically pure a-amino acids (Eq. 11.52).90... 

One of the exciting results to come out of heterogeneous catalysis research since the early 1980s is the discovery and development of catalysts that employ hydrogen peroxide to selectively oxidize organic compounds at low temperatures in the liquid phase. These catalysts are based on titanium, and the important discovery was a way to isolate titanium in framework locations of the inner cavities of zeolites (molecular sieves). Thus, mild oxidations may be run in water or water-soluble solvents. Practicing organic chemists now have a way to catalytically oxidize benzene to phenols alkanes to alcohols and ketones primary alcohols to aldehydes, acids, esters, and acetals secondary alcohols to ketones primary amines to oximes secondary amines to hydroxyl-amines and tertiary amines to amine oxides. 

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