Ethers methyl oxime

This series of rearrangements includes the dithia-Claisen rearrangement mentioned above (Section IV.E.l) as well as the palladium-catalyzed [3,3]-sigmatropic isomeriza-tions of allyl methyl N-aryldithiocarbonimidates 627 (refluxing dioxane, 20 h, 62-90%) (equation 275)376 and a Pd11-catalyzed tandem [2,3]-sigmatropic shift, followed by 1,3-dipolar cycloaddition which takes place at equilibrium between O-allyl ethers of oximes 628 and the corresponding N-allyl nitrones 629 (equation 276)377. 

Similarly, on-column methylation has been applied to carbamate pesticides containing an active N-H group. Wien and Tanaka (41) showed that N-aryl carbamates are methylated on-column with tri-methylanilinium hydroxide-methanol to give the intact N-methyl and N-aryl derivatives. On the other hand N-methyl, 0-aryl carbamates such as carbaryl or carbofuran yielded only the methyl ethers of their respective phenols. This work has now been extended to sulfur-containing carbamates such as methomyl, methio-carb, aldicarb, etc. (42-43). Here the oxime hydrolysis products of these carbamates are chromatographed as the 0-methyl oximes. 

When electroreduction was used, it was even possible to obtain cross-products, by coupling a ketone to an O-methyl oxime O-Methyl oxime ethers are coupled... 

Oximes may be alkylated at nitrogen or oxygen both types are electrolytically reducible [1,94,95] in their protonated form. The nitrones are generally also reducible in alkaline solution, whereas the O-methyl ethers of oximes are not reducible in ordinary media containing alkali metal ions. In solutions containing quaternary ammonium /j-toluenesul-fonates, some 0-alkylated oximes give a polarographic wave,... 

The resulting MO-TMS derivatives of numerous important compounds of this class are characterized by standard mass spectra and GC retention indices on standard nonpolar phases for their identification. The use of most active silylating reagents permits us to exclude the stage of O-methyl oxime formation, so far as ketosteroids can form the enol-TMS ethers. For example, androstenedione (II) gives the bis-O-TMS derivative ... 

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]. 

O-methyl oxime ether of 2-acetonaphthone has also been reported to undergo facile syn -> anti photoisomerization.6 The composition of the photostationary state appears to be concentration-dependent with the sy/i-isomer predominating at low concentrations. Evidence supporting the involvement of the singlet state was obtained from fluorescence-quenching studies and from photosensitization experiments. 

Dimethyl (Z)-a-hydroxyiminobenzylphosphonates undergo fragmentation to benzoni-trile and dimethyl hydrogenphosphate . A four-centred cyclic mechanism was suggested for this reaction (equation 122). The fragmentation of 0-methyl oxime ethers required a much higher temperature and it was found to yield trimethyl phosphate, in addition to benzonitrile . The rate and the ease of this reaction are influenced by the groups attached to the phosphorus. For example, in a-hydroxyiminobenzylphosphonate esterified with the... 

Trioxazines. Condensation of carbonyl oxides (from ozonolysis of vinyl ethers or 0-methyl oximes) with nitrones (Scheme 35). 

Mesityl oxide Methyl benzoate Nitroethane Propyl alcohol Propylene dichloride Tetrahydrofurfuryl alcohol Trichloroethylene solvent, cellulose ethers Acetone oxime Acetophenone Butyl benzoate Butyl formate Cyclohexane Cyclohexyl acetate Dibutyl tartrate Diethyl oxalate Epichlorohydrin Ethyl butyrate Ethylene glycol diacetate Ethyl-(S)-lactate Ethyl propionate Isopropyl butyrate Mesityl oxide... 

Sodium 9-fluorenone oximate, as dissociated ions (114), is alkylated to the extent of 65% at O and 35% at N. When existing as ion pairs the oximate reacts to give 30% 0-methyl product. In the presence of a crown ether the oximate ion undergoes almost exclusive (95-99%) 0-methylation with MeOTs and 0/N-methylation (65 35) with Mel (115). Addition of NaBPh4 to suppress dissociation of the sodium oximate reduces the alkylation with both MeOTs and Mel to nearly the same rate and gives essentially an identical proportion (ca. 43 57) of 0/N-alkylation. Under such conditions, the two heteroatoms are of approximately the same hardness. 

Steroids Biie acids Fatty acids Urinary acids Ketones Prostagiandins Oximes, TMS, t-BDMS ethers Methyl esters, TMS ethers Methyl esters, TMS, t-BDMS esters Methyl esters, TMS, t-BDMS esters Oximes Methyl esters, oximes, TMS, ethers Steroid profiles Liver disease, peroxisomal deficiencies Phospholipids, triglycerides Acidurias, diabetes Diabetes Healing processes, pain... 

SCHEME 7.64 Nitrate-promoted palladium-catalyzed C—H fluorination using O-methyl oxime ethers as directing groups [102]. 

This is a challenging reaction, and general approaches are rare. Many reactions tend to be substrate specific. For example, methyl oxime ethers can be converted into vinyl fluorides under very mild conditions using silver salts and NFSI as the fluorine source [102]... 

CH3ONH2 HCI results in methyl ethers of oximes 85a,b and 86a. Acylation of oximes 44a and 52 with benzoyl chloride leads to the corresponding derivatives of oximes 85c and 86c, and treatment with p-toluenesulfochlor-ide gives nitriles 87 and 88. Nitriles 87 and 88 were also prepared by... 

---