Hydrazine and Hydroxylamine

The chromate(V) metal-oxo complex [L2CrO] (L3 = 2-ethyl-2-hydroxybutyrato) converts hydroxylamine to Cr-NO complexes by prior loss of LH , coordination of NH2OH, and a pair of two-electron reactions which occur in rapid succession, leading ultimately to the (formally) Cr(I)-NO complexes, [(LH)2Cr(OH)(NO)] and [LCr(0H)(H20)(N0)]. 

Hydroxylamine and hydrazine react with [AuClJ in aqueous HCl according to equations (7)-(10)  

In both cases it is proposed (albeit on evidence we consider to be scant) that the reactions proceed by single-electron transfer, forming Au(II) and radicals (e.g., [AuCU] + NHjOH - Au(II) + H2NO + 2H ), followed by further rapid (but unverified) steps. The acid ionization of HAuCU (Ka = 1.01 M) was invoked in the second of these reactions, studied over the range 0.20-2.00 M H , whereas in the first, the same authors treat it over a range of 0.1-1.00 M as a more one-sided equilibrium, with HAUCI4 the predominant but unreactive form. 

The initial rates of oxidation of N2H by Fe in aqueous HCIO4 are reproducible only for a given stock solution of iron(III) perchlorate (otherwise scatter of 60-100% is noted). In light of this problem, and also because the rate constants tabulated and the data depicted disagree numerically, it will not be considered further. The oxidation of NH2OH by the peroxoacid H3PO5 is catalyzed by 

The Mn(III) complex [Mn(cdta)H20], with H4cdta = trans-l,2-cyclo-hexanetetra-acetic acid, oxidizes hydrazine by a rate law in which the major term is fc[Mn(III)][N2H5][H ] , whereas its oxidation of hydroxylamine is kinetically more complex and shows a quadratic dependence on hydroxylamine and a more complex dependence on Still unresolved are 

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The 1,2,4-oxadiazole dioxolanes 144 react with hydroxylamine and hydrazines to form the 5-pyrazole- and isoxazole-substituted 1,2,4-oxadiazoles 146 via the dioxolane ring-opened intermediates 145 (Scheme 17). Reaction of compounds 144 with amidine or guanidine salts allows access to pyrimidine substituted analogues 147, via intermediate 145 (X = C(NH)R1), albeit in lower yield <1996JHC1943, 1998JHC161>. 

The conjugate addition of activated nitrogen nucleophiles, such as hydroxylamine and hydrazine derivatives, to a,/3-unsaturated bicyclic lactam 284 gave the corresponding /3-amino product 285 in good yield and excellent diastereoselectivity. These products can be manipulated to afford enantiopure /3-aminopyrrolidinones of potential application as conformationally constrained, substituted glutamate templates (Equation 45) <2001J(P1)2997>. 

The anammox catabolism, an exceptionally slow process generating toxic intermediates (hydroxylamine and hydrazin), takes place in an intracytoplasmic compartment called the anammoxosome. A surrounding impermeable membrane protects the cytoplasm from the toxic molecules produced inside this organelle-like structure. Such a tight barrier against diffusion seems to be realised by four-membered aliphatic cyclobutane rings that have been found... 

In our hands, base-activated phosphoramidite-Ir complexes were not suited for the allylation of hydroxylamine and hydrazine derivatives (R. Weihofen and G. Helmchen, unpublished results). However, interesting results were obtained by Takemoto and coworkers with Pybox type ligands (Scheme 9.30) [40]. Phosphates... 

Derivatives containing Hydroxylamine and Hydrazine in >lace of Ammonia. 

Ammino-derivatives of Platinum Salts—Derivatives of Platinous Salts— Derivatives of Platinio Saits—Derivatives containing Hydroxylamine and Hydrazine in place of Ammonia—Symmetrical and Asymmetrical Compounds—Diplato-animino-salts—Diplati-ammino-salts. 

This enzyme system catalyzes the oxidation of various nitrogen-, sulfur -, and phosphorus-containing compounds, which tend to be nucleophilic, although compounds with an anionic group are not substrates. For example, the N-oxidation of trimethylamine (Fig. 4.19) is catalyzed by this enzyme, but also the hydroxylation of secondary amines, imines, and arylamines and the oxidation of hydroxylamines and hydrazines ... 

Hydroxylamines and hydrazines can be acylated on insoluble supports using the same type of acylating agent as is used for the acylation of amines [146-149]. Because of their higher nucleophilicity, hydroxylamines or hydrazines can be acylated more readily than amines, and unreactive acylating agents such as carboxylic esters can sometimes be successfully employed (Table 13.10). Polystyrene-bound O-alkyl hydroxamic acids can be N-alkylated by treatment with reactive alkyl halides and bases such as DBU (Entry 5, Table 13.10). 

Figure 2.8 A Brpnsted plot for the nucleophilic attack of primary and secondary amines of p-nitrophenyl acetate. Note that the a -effect nucleophiles—semicarbazide (SC), hydroxylamine, and hydrazine—are more reactive than would be expected from their pAT s. [From W. P. Jencks and M. Gilchrist, J. Am. Chem. Soc. 90,2622 (1968).]...

This reaction scheme was later confirmed for the reduction of oximes in acidic solution by isolation of the intermediate ketimine in two cases 143-). However, in alkaline medium, reduction of the C=N bond in oximes and semicarbazones pre-ceds splitting of the N-Y bond, so that hydroxylamines and hydrazines may be obtained144 The stereochemistry of the electrochemical and chemical (H2/Pt, Na/EtOH) reduction of several imines to amines has been compared recently by Fry and Reed 144b ... 

In practice hydroxylamine and hydrazine are very reactive nucleophiles, far more so than might be expected from consideration of simple physical parameters. The inceased nucleophilicity of a heteroatom when bonded to a second hereoatom is known as the a effect. For a theoretical rationalisation of the a effect in terms of frontier obitals see Fleming, 1976. 

Although there is ample evidence for nucleophilic additions to benzyne la> and some other unstable angle strained cycloalkyne intermediates 15,27,31,205 207), only a few addition reactions to isolable angle strained cycloalkynes are known which can be classified as nucleophilic. Hydroxylamine and hydrazine add to (31) to yield the corresponding oxime and hydrazone, resp. 208). 

Key Mechanism 18-5 Formation of Imines 851 18-16 Condensations with Hydroxylamine and Hydrazines 853 Summary Condensations of Amines with Ketones and Aldehydes 854 18-17 Formation of Acetals 855... 

Similar results are obtained with iron(II) sulphate solution. Reduction also occurs with hydroxylamine and hydrazine salts, and ascorbic acid. 

Amines and hydroxylamine and hydrazine derivatives react with 36 at the lactim ether group and not at the keto group76 88 [Eq. (2)]. By contrast, in the reaction between the imidochloride of isatin and tosylhydrazine (or aniline) the keto group at position 3 was found to be attacked and at the same time the imidochloride was transformed into the lactam89 [Eq. (3)]. Thus it may be argued that, at least in the case of the isatin derivatives, the lactim ether function is more reactive than the imidochloride. 

There is a general requirement for pyridoxal-5-phosphate (24, 25, 27, 44) although not all of the activity lost on dialysis is restored by adding the cofactor. This requirement explains the inhibition by hydroxylamine and hydrazine (24, 25). The reaction is a typical pyridoxal-5-phosphate catalyzed a,/ -elimination with a mechanism similar to serine dehydrase and cysteine desulfhydrase (45). The coenzyme is probably bound as a Schiff base with an amino group of the enzyme since there is an absorption maximum at 415 nm in solutions of the purified garlic enzyme (40). The inhibition by L-cysteine is presumably caused by formation of a thiazolidine with the coenzyme (46). Added pyridoxal-5-phosphate also combines directly with the substrate. The dissociation constant for the complex is about 5 X lO M. When this is taken into account, the dissociation constant of the holoenzyme can be shown to be about 5 X 10 M (47). The higher enzyme activity in pyrophosphate buflFer than in Tris or phosphate may be explained by pyrophosphate chelation of metal ions which otherwise form tighter complexes with the substrate and coenzyme (47). This decreases the availability of added coenzyme. 

Blumenfeld and Gallop (1962b) have used lithium borohydride reduction, with subsequent chromatographic separation of the amino alcohols produced, to identify the carboxyl donor of the ester links previously found by Gallop et al. (1959) using hydroxylamine and hydrazine. The peaks obtained on the chromatogram for the two products in question, namely homoserine and /3-amino-7-hydroxybutyric acid, are very small, but nonetheless seem to establish that a- and /3-carboxyl groups of aspartic acid participate in the hydroxylamine-sensitive links. 

To conclude on ester links, there is clearly much to be considered in the work cpioted using lithium borohydride, hydroxylamine, and hydrazine. 

Figure 13.27. Selectivity of the Sodium Channel. The ionic selectivity of the sodium channel partly depends on steric factors. Sodium and lithium ions, together with a water molecule, fit in the channel, as do hydroxylamine and hydrazine. In contrast, K+ with a water molecule is too large. [After R. D. Keynes. Ion channels in the nerve-cell membrane. Copyright 1979 by Scientific American, Inc. All rights reserved.]...

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