Oximes titanium chloride

The production of aldehyde groups through periodate oxidation and subsequent formation of oxime groups is being used as a basis for an anionic initiation of grafting with titanium chloride as catalyst according to a process claimed by Asahi Chemical Industries Company (135). With this method styrene was grafted onto viscose rayon. Also bi- and tri-valent vanadium salts can be used as initiators. 

Tertiary amine TV-oxides are rapidly deoxygenated by carbon disulphide1112. Oximes are reduced to primary amines by titanium(III) chloride in the presence of sodium cyanoborohydride, NaBTpCN1. The combined action of sodium borohydride and a chiral... 

In a communication by Tanimoto and coworkers, ketene O-alkyl O -trunethylsilyl acetals 49 provide either a-nitroso esters 50 or their oximes 51 on reaction with nitric oxide or isoamyl nitrite in the presence of titanium(IV) chloride (Scheme 29). These reactions seem to provide a relatively direct way to introduce a nitrogen substituent at the a-carbon atom of carboxylic esters. 

Following the same procedure, formation of the imine 6D and subsequent deprotonation with two equivalents of butyllithium followed by alkylation, either enantiomer of the a-substituted benzylamines could he obtained with nearly complete stereocontrol. Unfortunately only poor yields are obtained51,52,53. The (-)-(15,25, 55)-2-hydroxy-3-pinanone derived from ( + )-a-pinene resulted in the formation of the R-configurated benzylamines, conversely the ( + )-2-hy-droxy-3-pinanone derivative led to the (S )-benzylamine product. It has been shown that the high stereocontrol occurs within the alkylation step. The chiral auxiliary can be recovered without racemization from the oxime with aqueous titanium(III) chloride. 

Isoxazolines have been converted into unsaturated oximes, and thence into enones (76AG(E)50). Treatment of the isoxazoline (523), for example, with lithium diisopropylamide gave the ring cleavage product (524) which reacted with titanium(III) chloride to furnish enone (525 Scheme 115). Oxime formation has been shown to proceed via the anion (526) as revealed by deuteration studies. 

Potassium hydroxide, 258 Trimethylsilyl chlorochromate, 327 of carbon-carbon double bonds substituted by heteroatoms m-Chloroperbenzoic acid, 76 of oximes to carbonyl compounds Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Trimethylsilyl chlorochromate, 327 of protected alcohols Chlorodimethylthexylsilane, 74 Formic acid, 137 p-Methoxyphenol, 181 of thioacetals and -ketals Methoxy(phenylthio)trimethyl-silylmethane, 182... 

Oxime deoxygenation by titanium(III) chloride spurred investigation of this agent for reducing nitro aliphatics the method is applicable to other nitro compounds. - The active species are thought to be ArN02H and a hydrolyzed form of titanium(II). The reaction conditions have been optimized for the reduction of aromatic and even heteroaromatic nitro compounds. ... 

Low-valent metal salts have been used to bring about reductive cleavage of oximes. Corey and Rich-man used chromium(II) acetate to convert O-acetyl ketoximes into imines, which were hydrolyzed to ketones. " Aqueous titanium(III) chloride and vanadium(II) salts also reduce oximes again, the imines are usually hydrolyzed in situ, but some hindered imines, such as compound (37), are isolable." A method of preventing hydrolysis is to carry out the reduction in anhydrous conditions in the presence of an acylating agent. The products of such reactions, when applied to oximes of enolizable ketones, are en-amides. For example, these ketoximes are converted into A/-formylenamines when heated in acetonitrile with anhydrous titanium(III) acetate and acetic formic anhydride cyclohexanone oxime gives the en-amide (38 97% Scheme 22)." This type of reduction has been used by Barton and coworkers to prepare enamides from steroidal oximes. They reported that the reaction could be performed by acetic... 

Indirect replacement of the a-hydrogen atom of carboxylic esters by the nitroso group is remarkable. This procedure uses ketene 0-alkyl O -silyl acetals (1), generated from carboxylic esters, which are treated with nitric oxide or isopentyl nitrite in the presence of titanium(IV) chloride. In the absence of an a-hydrogen a-nitroso esters (2) are obtained. a-Nitroso esters with an a-hydrogen undergo isomerization to oximes of a-keto esters (3 equation 1). Similarly, silyl enol ethers of aldehydes or ketones can be used instead of the carbonyl compound itself for nitrosation. Thus, treatment of enol ether (4) with nitro-syl chloride gives the a-nitroso aldehyde (5 equation 2), which is quite stable at 0 C, but dimerizes at room temperature. 

The total synthesis of spirotryprostatin B was accomplished by K. Fuji et al using an asymmetric nitroolefination to establish the quaternary stereocenter." The conversion of the nitroolefin to the corresponding aldehyde was carried out under reductive conditions using excess titanium(lll) chloride in aqueous solution. The initially formed aldehyde oxime was hydrolyzed in situ by the excess ammonium acetate. 

The reduction of ketoximes with titanium(iu) chloride is noted in a partial synthesis of erythromycylamine in this case, the intermediate imine is stable and can be further reduced, though normally imine hydrolysis is rapid and ketones are obtained in high yield. This observation has been utilized to effect conversion of a nitro-compound into a ketone. In search of a route to 1,4-diketones via conjugate addition of a masked carbonyl anion to an ajS-unsaturated ketone, McMurry considered Michael addition with a nitro-alkane. Treatment of the resulting y-nitroketone with titanium(m) chloride afforded the required 1,4-diketone (148) in excellent yield, presumably by sequential intermediacy of the oxime and the imine this mild conversion avoids the harsh conditions of the alternative Nef procedure (Scheme 69). 

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