Amines V-oxides

Azomethine ylides such as 64 can be generated from tertiary amine /V-oxides (63) by reaction with lithium diisopropylamide (LDA) (Scheme 12.22) (97). Several different chiral -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%. 

There have been comprehensive reviews on the coordination chemistry of aromatic JV-oxides by Garvey et al. (up to 1968)67 and Karayannis et al. (up to 1971),68 the latter including a short section on aliphatic amine (V-oxides and secondary amine nitroxide free radicals. A further review by Karayannis et al. (up to 1975)69 covers mono- and di-oxides of bipyridyl, o-phenanthroline and some diazines. 

Polonovski reaction. Demethylation of tertiary (or heterocyclic) amine V-oxides on treatment with acetyl chloride or acetic anhydride to give N-acylated secondary amines and formaldehyde, along with O-acylated aminophenols as a result of a side reaction. 

Analytical characterization Mass spectrometry2,4 is suitable for detecting triethylcyclotriboroxane (base peak m/z = 139) in tetraethyldiboroxane (base peak m/z = 125). 0.5% Triethylcyclotriboroxane (511b = 33 ppm) or triethylborane (fi j j = 86 ppm) in tetraethyldiboroxane (5 2 2 B = 53.3 ppm) can be identified by nB-NMR spectroscopy.5 Triethylcyclotriboroxane or triethylborane amounts can be determined quantitatively by finding the Bc-values using the trimethyl-amine /V-oxide method6 in conjunction with the combined pyridine /V-oxide/ trimethylamine, /V-oxide method and the total boron content. 

A possibility for azomethine ylide generation from 4-isoxazolines was first suggested by Baldwin, who demonstrated a thermal N—O bond cleavage of 4-isoxazoline systems (68JA5325). Cycloaddition of N-methylene(t-butyl)-amine V-oxide to dimethyl acetylenedicarboxylate takes place at 0°C, rapidly and quantitatively, to give 4-isoxazoline 146 (R = t-Bu, =R = COOMe), which isomerizes at 80°C into 4-oxazoline 148 (R = f-Bu, R = R = COOMe). The nitrone bearing an N-aryl substituent and the same acetylene directly afford 2-acylaziridine 147 (R = 2,4,6-trimethylphenyl, R = R = COOMe). Reaction of the N-t-butylnitrone with 3-methylbutyn-... 

Scheme 15.15 Reetz s diastereoselective r2.31-Meisenheimer rearrangement of enantioenriched amine /V-oxides with carbon stereorenters.

FIG. 8 Cumulative enthalpy isotherms of displacement of water by V,V-dimethyldecyl-amine-V-oxide onto CPG silica glass (O) and Vulcan 3G graphitized carbon black ( ) at 298.15 K. 

The cellulose dissolving potential of the amine oxide family was first realized (79) in 1939, but it was not until 1969 that Eastman Kodak described the use of cycHc mono(/V-methy1amine-/V-oxide) compounds, eg, /V-methylmorpho1ine-/V-oxide [7529-22-8] (NMMO), as a solvent size for strengthening paper (80) by partially dissolving the cellulose fibers. 

It has been proposed that the ring-expansion reaction is initiated by attack of the base at position 2 of the quinazoline oxide, which is rendered electron deficient by the inductive effect of the (V-oxide group. In fact, 2-(Chloromethyl)quinazolines, compounds that lack this feature, react with amines to give only simple substitution products.1133... 

CN 7-chloro-/V-methyl-5-phenyl-37/-1,4-benzodiazepin-2-amine 4-oxide... 

There is an extensive literature on the use of 2,1,3-benzoxadiazole 1-oxide [often called benzofuroxan(e) (BFO) (462)] as a substrate for the primary synthesis of quinoxaline 1,4-dioxides and occasionally quinoxaline mono-V-oxides or even simple quinoxalines. Very few substituted derivatives of the parent substrate (462) have been employed in recent years. The general mechanism clearly involves a fission (usually amine-catalyzed) of the oxadiazole ring followed by reaction with an ancillary synthon. The following examples are divided according to the type of synthon employed. 

The effects of various metal oxides and salts which promote ignition of amine-red fuming nitric acid systems were examined. Among soluble catalysts, copperQ oxide, ammonium metavanadate, sodium metavanadate, iron(III) chloride (and potassium hexacyanoferrate(II) with o-toluidine) are most effective. Of the insoluble materials, copper(II) oxide, iron(III) oxide, vanadium(V) oxide, potassium chromate, potassium dichromate, potassium hexacyanoferrate(III) and sodium pentacyanonitrosylferrate(II) were effective. 

The affinity of [Au(CN)2] for primary, secondary, and tertiary amines is very low at pH values typical for cyanide feed solutions, but in 1983 Mooiman et al. showed that the addition of solvating phosphorus(V) oxides enhanced extraction at higher pH.335,336 During the course of this work it was discovered that TBP and DBBP (see Table 6) could themselves extract gold.337 This led to subsequent investigations on phosphates and phosphorus oxides.333... 

The synergistic action of a phenol and aromatic amine mixture on hydrocarbon oxidation was found by Karpukhina et al. [16]. A synergistic effect of binary mixtures of some phenols and aromatic amines in oxidizing hydrocarbon is related to the interaction of inhibitors and their radicals [16-26]. In the case of a combined addition of phenyl-A-2-naphthylamine and 2,6-bis(l,l-dimethylethyl)phenol to oxidizing ethylbenzene (v, = const, 343 K), the consumption of amine begins only after the phenol has been exhausted [16], in spite of the fact that peroxyl radicals interact with amine more rapidly than with phenol (7c7 (amine) = 1.3 x 105 and /c7 (phenol) = 1.3 x 104 L mol 1 s respectively 333 K). This phenomenon can be explained in terms of the fast equilibrium reaction [27-30] ... 

In summary, the reaction of osmium tetroxide with alkenes is a reliable and selective transformation. Chiral diamines and cinchona alkakoid are most frequently used as chiral auxiliaries. Complexes derived from osmium tetroxide with diamines do not undergo catalytic turnover, whereas dihydroquinidine and dihydroquinine derivatives have been found to be very effective catalysts for the oxidation of a variety of alkenes. OsC>4 can be used catalytically in the presence of a secondary oxygen donor (e.g., H202, TBHP, A -methylmorpholine-/V-oxide, sodium periodate, 02, sodium hypochlorite, potassium ferricyanide). Furthermore, a remarkable rate enhancement occurs with the addition of a nucleophilic ligand such as pyridine or a tertiary amine. Table 4-11 lists the preferred chiral ligands for the dihydroxylation of a variety of olefins.61 Table 4-12 lists the recommended ligands for each class of olefins. 

Some reactions of 2,2 -bipyridine /V-oxides have been reported. The l,T-dioxide is nitrated readily to 4,4 -dinitro-2,2 -bipyridine 1,T-dioxide. ° ° °" 2,2 -Bipyridine 1-oxide is also nitrated in the 4 position. The nitro groups in 4,4 -dinitro-2,2 -bipyridine l,T-dioxide are reactive, being replaced by chlorine with concentrated hydrochloric acid," by bromine with acetyl bromide, by hydroxyl with dilute sulfuric acid, and by alkoxy groups with sodium alkoxides. Some of the dialkoxy derivatives are useful catalysts for the oxidation of aromatic compounds. The dinitro dioxide is deoxygenated to 4,4 -dinitro-2,2 -bipyridine with phosphorus trichloride in chloroform, and other substituted l,T-dioxides behave similarly, but with phosphorus trichloride alone, 4,4 -dichloro-2,2 -bipyridine results. The dinitro dioxide is reduced by iron powder in acetic acid to 4,4 -diamino-2,2 -bipyridine, whereas 4,4 -dichloro-2,2 -bipyridine l,T-dioxide is converted to its 4,4 -diamino analogs with amines. Related reactions have been described. ... 

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