Tertiary amine A-oxide

Sigmatropic rearrangement of tertiary amine A -oxides to hydroxylamines ... 

Azomethine ylides such as 64 can be generated from tertiary amine A-oxides (63) by reaction with lithium diisopropylamide (EDA) (Scheme 12.22) (97). Several different chiral A -substituted azomethine ylides were prepared in this manner. The best results were obtained when using 64 in 1,3-dipolar cycloaddition with alkenes, but the de values obtained of the product 65 were <60%. 

Oxo-rhenium complexes can catalyze various OAT reactions between suitable oxo-donors (XO = sulfoxides (R2SO) tertiary amine A-oxides (R3NO) pyridine A-oxide (C5H5NO, PyO) triphenyl-phosphine, -arsine, or -stilbene oxide (R3AO) (A = P, As, Sb) peroxides (Bn OOH, H2O2) ... 

Te catalyst) reduces tertiary amine A -oxides to the corresponding amines Azides are reduced to primary amines by sodium hydrogen telluride ... 

Vinylogous trifluoromethyl amides. The Potier-Polonovski rearrangement of tertiary amine A(-oxides induced by (CFjCOjjO is frequently followed by trifluoroacetylation. This method is most suitable for the synthesis of (-)-altemicidin. ... 

The tertiary amine A-oxides with a (3-hydrogen in the alkyl substituted group may also undergo Cope elimination to give a hydroxylamine and an olefin. The A-oxide metabolite of SC-57461 was found to be unstable in organic... 

A significant advance in the Pauson-Khand reaction was made by the discovery that various additives, such as tertiary amine A-oxides, promote the cycloaddition reaction. For example, treatment of the dicobalt complexed alkyne 187 with trimethylamine A-oxide at only 0 °C provides the cyclopentenone 188 in good yield (1.192). More recent advances have been made in catalytic Pauson-Khand reactions. " Only 3 mol% of dicobalt octacarbonyl [Co2(CO)8] under one atmosphere of CO effects the formation of the cyclopentenone 188 from the alkyne 189 in benzene at 70 °C (an improvement in the yield to 90% was achieved in the presence of the additive Bu3P=S) (1.193). " ... 

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

It is accepted that this reaction involves the formation of the alkynedicobalt hexacarbonyl complex from an alkyne and Co2(CO)s by the evolving of two CO ligands, followed by the alkene coordination at one of the two enantiotopic Co atoms with concomitant CO insertion, and final reductive elimination of the metal to an a,(3-unsaturated cyclopentenone. In the traditional protocol, the reaction mixture is heated in toluene at 110°C, or tertiary amine A-oxides are added to promote the reaction at ambient temperature. For the purpose of stereochemical control, many Pauson-Khand reactions are designed as intramolecular reactions P " or using cyclic alkenes, such as norbornene. It has been found that the reactivity of cyclic alkenes is in the order of cyclohexene < cyclopentene < norbornene. For the intermolecular Pauson-Khand reaction, alkene is positioned adjacent to the less bulky acetylenic substituent during coordination because of steric hindrance, and a subsequent C-C bond forms between an alkenic... 

The formation of N-oxides of tertiary amines and demethylation of secondary amines are biochemical processes which may also be involved in detoxification. In the case of A, iV-dimethylaniline, the N-oxide is considered to be the possible intermediate in its NADPH- and oxygen-dependent oxidative demethylation. The formation of this A -oxide appears to be catalyzed via a flavoprotein oxidase (509). Tertiary amine A -oxides, thus formed, are often excreted in urine. In the case of A -methyl-4-aminoazobenzene (MAB), demethylation to 4-aminoazoben-zene (AB) appears to occur via a cytochrome P-450 mediated oxidation. Since an A -methyl substituent is regarded as essential for carcinogenic activity among derivatives of AB, this oxidative demethylation would be a specific mode of detoxifying this carcinogenic aromatic amine. 

Sugiura M, Iwasaki K, Kato R. Reduction of tertiary amine A -oxides by liver microsomal cytochrome P-450. Mol Pharmacol 1976 12 322-334. 

The combination of A -bromoacetamidc, silver acetate, and dry acetic acid has been shown to be superior to Woodward s procedure for the rfy-hydroxylation of olefins. Work up of the reaction mixture is simply effected by hydrolysis of the dioxolenium ion, followed by cleavage of the hydroxyacetate intermediate with lithium aluminium hydride. The use of a co-oxidant, such as sodium chlorate or hydrogen peroxide, allows the addition of catalytic quantities of osmium tetroxide to prepare c/y-diols from olefins. However the reaction is often complicated by further oxidation of the glycol to the a-ketol. The use of tertiary amine A -oxides, particularly A -methylmorpholine A -oxide, prevents this oxidation and gives higher yields of the desired product (Table 6). Another variation on this theme employs... 

Transalkylation of Tertiary Amine A-Oxides. N- t-Butyldimethylsilyloxy)-A-methylpiperidinium triflate is quantitatively formed from the reaction of A-methylpiperidine A-oxide (eq 13). The resulting amine salts derived from various trialkylamine A-oxides undergo transalkylation by treatment with Methyllithium in THF at 0 °C followed by alkyl halides and Tetra-n-butylammonium Fluoride in a sealed tube at 110 °C for 10 h, to afford trisubstituted amines (eq 14). ... 

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