Amine oxides deoxygenation

Divalent chromium reduces triple bonds to double bonds (trans where applicable) [195], enediones to diones [196], epoxides to alkenes [192] and aromatic nitroso, nitro and azoxy compounds to amines [190], deoxygenates amine oxides [191], and replaces halogens by hydrogen [197,198],... 

Deoxygenation. Amine oxides are deoxygenated by heating with Cul and i-Pr2NEt in THF. ... 

Deoxygenation. The Tebbe reagent deoxygenates amine oxides, sulfoxides, and selenoxides. 

In the pyrolysis of pure amine oxides, temperature has a significant effect on the ratio of products obtained (22). The principal reaction during thermal decomposition of /V,/V-dimetby11 amyl amine oxide [1643-20-5] at 80—100°C is deoxygenation to /V,/V-dimetby11 amyl amine [112-18-5] (lauryl = dodecyl). 

Reduction. Just as aromatic amine oxides are resistant to the foregoing decomposition reactions, they are more resistant than ahphatic amine oxides to reduction. Ahphatic amine oxides are readily reduced to tertiary amines by sulfurous acid at room temperature in contrast, few aromatic amine oxides can be reduced under these conditions. The ahphatic amine oxides can also be reduced by catalytic hydrogenation (27), with 2inc in acid, or with staimous chloride (28). For the aromatic amine oxides, catalytic hydrogenation with Raney nickel is a fairly general means of deoxygenation (29). Iron in acetic acid (30), phosphoms trichloride (31), and titanium trichloride (32) are also widely used systems for deoxygenation of aromatic amine oxides. 

Titanous chloride (titanium trichloride) is applied in aqueous solutions, sometimes in the presence of solvents increasing the miscibility of organic compounds with the aqueous phase [199, 200]. Its applications are reduction of nitro compounds [201] and cleavage of nitrogen-nitrogen bonds [202] but it is also an excellent reagent for deoxygenation of sulfoxides [203] and amine oxides [199] (Procedure 38, p. 214). 

A-Amine oxides can be reduced (deoxygenated) to tertiary amines. Such a reaction is very desirable, especially in aromatic nitrogen-containing heterocycles where conversion to amine oxides makes possible electrophilic substitution of the aromatic rings in different positions than it occurs in the parent heterocyclic compounds. The reduction is very easy and is accomplished by catalytic hydrogenation over palladium [736, 737], by borane [738], by iron in... 

Deoxygenation of amine oxides. Trialkylamine N-oxides and dialkylarylam-ine N-oxides are converted to the tertiary amines on reaction with this anhydride in CH2C12 at 25°.1... 

Although molybdenum and tungsten enzymes carry the name of a single substrate, they are often not as selective as this nomenclature suggests. Many of the enzymes process more than one substrate, both in vivo and in vitro. Several enzymes can function as both oxidases and reductases, for example, xanthine oxidases not only oxidize purines but can deoxygenate amine N-oxides [82]. There are also sets of enzymes that catalyze the same reaction but in opposite directions. These enzymes include aldehyde and formate oxidases/carboxylic acid reductase [31,75] and nitrate reductase/nitrite oxidase [83-87]. These complementary enzymes have considerable sequence homology, and the direction of the preferred catalytic reaction depends on the electrochemical reduction potentials of the redox partners that have evolved to couple the reactions to cellular redox systems and metabolic requirements. 

Deoxygeuation of N-oxides. Amine oxides are deoxygenated to the corresponding amines by reaction with iron pentacarbonyl in boiling di-n-butyl ether. ... 

Deoxygenation of Nitrones, Nitrile Oxides and Tertiary Amine Oxides... 

Methods of deoxygenation of nitrones (28), nitrile oxides (29), heteroaromatic N-oxides (30) and tertiary amine oxides (31) are described in this section. There are some reagents, such as trialkyl phosphites, which can deoxygenate compounds of all these types as well as those in the preceding section, whereas others are more limited in scope. Oae and coworkers have outlined three distinct mechanistic types of deoxygenation process, which are illustrated in Scheme 17. Clearly, a mechanism of type C will not apply to tertiary amine oxides (31) on the other hand, these compounds are more easily deoxygenated than heteroaromatic N-oxides, such as (30), by some reagents because the aromatic N-oxides are inherently more stable. 

Rosenau, T., Potthast, A., Ebner, G., Kosma, P. Deoxygenation of amine oxides by in-situ-generated formic pivalic anhydride. Syn/eff 1999, 623-625. 

Deoxygenation of amine oxides. Since transformations sometimes can be accomplished more satisfactorily with a pyridine-1-oxide than with the pyridine itself, an efficient method of deoxygenation with PCI3 introduced by Ochiai has found wide usage. For example, 1 g. of 4-nitropyridine-1-oxide was suspended in 15 ml. of cold... 

Hexachlorodisilane has been found to be a convenient deoxygenating agent of amine oxides and sulfoxides, and has been used in the synthesis of condensed bridged phosphinesIn addition, the first and only stereospecific desulfurization of phosphine sulfides reported to date was also accom-... 

Reductive desulfurization of the dithioketals 5.14 and 5.15 is performed under the same conditions as for thioethers [G02] LAH in the presence of copper salts or borohydrides in the presence of nickel salts (Figure 5.8). The deoxygenation of tertiary amine-oxides such as 5.16 and 5.17 can be performed with borohydride exchange resin-copper sulfate in methanol at room temperature or under reflux. This reaction tolerates other functional groups such as carbon-carbon double bonds, chlorides, epoxides, esters, amides, nitriles, sulfoxides, and sulfones [SA4] (Figure 5.8). 

Tervalent phosphorus compounds (phosphorous derivatives) are weil-established reagents for the deoxygenation of amine oxides and nitrones, and they provide a clean and convenient method for the preparation of furazans from furoxans. Mukaiyama et al.425 and Grundmann426 used trialkylphosphites, and they have been widely employed since that time, both with and without solvents.80,85,93,95,97,352 The simple dialkyl- and diarylfuroxans usually require more vigorous conditions (e.g., refluxing triethyl phosphite) than do strained derivatives or the benzofuroxans.85,97... 

Deoxygenation. Removal of the oxygen atom from amine oxides with the mixed anhydride at the temperature of ice is quite convenient. The mixed anhydride is formed and used in situ from HCOONa and pivaloyl chloride. 

The course of the reaction between A -methylmorpholine-A -oxide 290 (NMMO) and cyanuric chloride is strictly dependent on the hydrate water content of the amine oxide (Scheme 55). The reaction can be conducted in such a way that a clean deoxygenative demethylation is achieved <2002T9809>. 

Burka LT, Guengerich FP, Willard RJ, Macdonald TL. Mechanism of cytochrome P-450 catalysis. Mechanism of N-dealkylation and amine oxide deoxygenation. J Am Chem Soc 1985 107 2549-2551. 

Deoxygemttion of amine oxides. Cbromous chloride is useful for deoxygenation of aromatic amine oxides (yields 60-90%). ... 

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