Dimethylhydroxylamine

A.A-Dimethylhydroxylamine reacts with 73a to give the chiral animation reagent 89 with retention of configuration at the phosphorus atom. On reacting (-)- 89 with... 

Hydroxylamine, JV-methylhydroxylamine and V,V-dimethylhydroxylamine were determined by ion chromatography. Amperometric detection using a GCE showed best sensitivity and selectivity, with injections of nanomole amounts620. 

Esters ofN,N-dialkylhydroxylamines ((acyloxy)amines) appear to be possible candidates for prodrugs of carboxylic acids, but more studies must be published before any firm conclusion can be drawn. First, there are indications of low acute toxicity for N,N-(1 al ky I hydroxy Iambics [87], Whether the same applies (acutely and chronically) to the pro-moieties after their release from the prodrugs is not known. A second argument is the low basicity of hydroxylamines (the pKa of Ar,AT-dimethylhydroxylamine is 5.2), and the expected lower basicity of O-acylatcd hydroxylamines. As a result, esters of hydroxylamines will be in the unprotonated, more lipophilic form at physiological pH and should be absorbed more readily than the corresponding carboxylic acid [88]. 

Dimethylethyl) -3- (methylthio) -1,2,4 -triazin-5 - (4 H) -one, see Metribuzin 7V,7V-Dimethylformamide, see Dimethylamine Dimethyl hydrogen phosphate, see Dichlorvos TV.O-Dimethylhydroxylamine, see Linuron 0,0-Dimethyl 5- (TV-hydroxymethylcarbamoyhnethyl) phosphorothioate, see Dimethoate 0,0-Dimethyl 5- (TV-hydroxymethylcarbamoyhnethyl) phosphorothiolate), see Dimethoate 0,0-Dimethyl 5- (A-methylcarbamoylmethyl) phosphorothiolate, see Dimethoate O, O-Dimethyl-0- (4- (methylthio) -m-tolyl) phosphate. 

Engelhard , G., Wallnofer, P.R., and Plapp, R. Identification of N, O-dimethylhydroxylamine as a microbial degradation product of the herbicide, linuron, Appl Microbiol, 23 664-666, 1972. 

Starting from AT-(Boc)-(S)-phenylalanine (77) the Weinreb amide was formed by a DCC-mediated condensation with AT,0-dimethylhydroxylamine. Treatment of the Weinreb amide with undecynyl lithium yielded the ynone... 

Addition of a lithiated secondary amine to an aldehyde both protects the aldehyde from attack by RLi and turns it into an ortholithiation directing group. The best lithioamines for this purpose are A-lithio-A-methylpiperazine 53, iV-lithio-iV,iV,iV -trimethylethylene-diamine 56 and Al-lithio-Al,0-dimethylhydroxylamine 58 , which optimize the opportunity for coordination of BuLi to the intermediate alkoxide (54) (Scheme 27) . ... 

We shall now compare some properties of prototypical examples of hydroxylamines, oximes and hydroxamic acids. These will be structures 1, 2 and 3 with methyl groups at the remaining positions, i.e. dimethylhydroxylamine (6), acetoxime (7) and acetohydroxamic acid (8). 

TABLE 3. Some computed properties of dimethylhydroxylamine (6), acetoxime (7) and acetohy-droxamic add (8) ... 

As points of reference, we will take two well-established hydrogen-bond donor/ acceptors, H2O and NH3. Their computed gas-phase Vs,max and Vs,mm are in Table 5, along with the same data for all of the molecules that have been discussed hydroxylamine (5), dimethylhydroxylamine (6), acetoxime (7), acetohydroxamic acid (8), and the isomeric pairs of oximes examined in the last section. Finally, we included an additional hydroxamic acid, 11, to see the effects of the strongly electron-withdrawing cyano group. 

Hydroxylamine and dimethylhydroxylamine, 5 and 6, are extremely weak acids, judging from how much less are their conjugate base /s.min than that of acetohydroxamic acid, 8. Accordingly the experimental p Ta of hydroxylamine, 5.94, must refer to its behavior as a base, with pX b = 8.06. Indeed its p Ta and its nitrogen /s.min are both quite similar to those of pyridine. 

Stolze, K., and Nohl, H. (1990a). Free radical intermediates in the oxidation of N-meth-ylhydroxylamine and N,N-dimethylhydroxylamine by oxyhemoglobin. Free Radical Res. Commun. 8, 123-131. 

The aqueous layer is combined with the two neutral aqueous extracts and acidified by addition of 45 ml. of concentrated hydrochloric acid. The solution is concentrated under reduced pressure at 60-70° until no more distillate comes over. The residue, which solidifies on cooling, is dried in a vacuum desiccator over potassium hydroxide pellets to yield 30.7-32.7 g. (90-96%) of crude N,N-dimethylhydroxylamine hydrochloride, m.p. 103-106° (sealed tube). Crystallization from 40 ml. of isopropyl alcohol gives 26.6-30.7 g. (78-90%) of the pure hydrochloride, m.p. 106-108° (sealed tube). 

N,N-Dimethylhydroxylamine has been prepared by the action of methylmagnesium iodide on ethyl nitrate.17... 

The reaction of 6-methylpyridine-3-carboxylic acid methyl ester with N,0-dimethylhydroxylamine and isopropyl-magnesium chloride in toluene gives the N-methoxyamide derivative (x), which is reduced with diisobutyl aluminium hydride (DIBAL) to afford 6-methylpyridine-3-carbaldehyde (xi). The reaction of the aldehyde (xi) with a phosphite provides the diphenyl phosphonate derivative, which is condensed with 4-(methylsulfonyl)benzaldehyde in the presence of potassium fe/f-butoxide in HF to yield the enimine (xii). Finally, this compound is hydrolyzed with HCI to yield the ketosulfone (ix). 

Horner-Emmons reaction of N-terminal blocked aldehyde 1 with sulfonylphosphonates in the presence of sodium hydride gives the amino acid vinyl sulfone 2, which is deprotected with acid and converted into its chloride or tosylate salt 3 and coupled by the mixed anhydride method with an N-terminal protected peptide or amino acid to give the desired peptide vinyl sulfones 4 (Scheme 2). 4 5 N-Terminal protected aldehydes 1 are obtained from reduction of Boc amino acid V-methoxy-A-methylamides (Weinreb amides, see Section 15.1.1) by lithium aluminum hydride. 9 The V-methoxy-V-methylamide derivatives are prepared by reaction of Boc amino acids with N,O-dimethylhydroxylamine hydrochloride in... 

ALDEHYDES Acetone cyanohydrin. Dichlorobis(cyclopentadienyl)titanium(II). Diisobutylaluminum hydride. Dimethylformamide. N,0-Dimclhylhydroxylamine hydrochloride. 4-Eormyl-l -methylpyridinium hcnzcncsuifonatc. N-Formylpiperidine. N.O-Dimethylhydroxylamine hydrochloride. 2-(2,6-l)imethylpipcridino)aectonitrile Mclhoxy(triniclhyl.silyl)incihyl lidiiiim... 

KETONES N.O-Dimethylhydroxylamine hydrochloride. N,N,-Diphenyl-/>-mcthoxyphenylchloromethyleniminum chloride. Formaldehyde dimethyl dithioacetal S.S-dioxidc 4-Fonmyl l methylpyridiniuni bcnzencsullonatc. l.ithi[Pg.651]

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