Methylhydroxylamine

The secondary allylic methylamine 324 can be prepared by the allylation of A -methylhydroxylamine (323), followed by hydrogenolysis[201], Monoallylation of hydroxylamine, which leads to primary allylamines, is achieved using the jV,0-bis-Boc-protected hydroxylatnine 326. N -... 

IV-Substituted derivatives have been prepared by the reaction of IV-methylhydroxylamine with phenylpropiolic esters or acid chlorides (71CPB1389), the cyclization of A"-substituted /3-ketohydroxamic acids or the reaction of phenylhydroxylamine with diketene (Scheme 150) 63GEP1146494). 

Compound (253) is formed from benzaldehyde and methylhydroxylamine-O-sulfonic acid in 35% yield. With ethyl-substituted chloramine or hydroxylamine-O-sulfonic acid yields do not exceed 10%, which is assumed to be due to steric hindrance and is foreseeable for both carbonyl addition and O —N bond formation. 

Mixtures of benzaldehyde, iV-methylhydroxylamine-O-sulfonic acid and dilute sodium hydroxide react to give oxaziranes [Eq. (7)]. The 2-mcthyl-3-phenyloxazirane (15) obtained (40% yield) is iden-... 

Thus the structure of the oxazirane must formally involve elimination of water from one molecule each of the carbonyl compound and of an alkyl hydroxylamine. (In the synthesis of oxazirane from N-methylhydroxylamine-O-sulfonic acid and benzaldehyde, this method... 

A simple chemical proof of structure of the diaziridines is given by the synthesis of the same diaziridine 42 from cyclohexanone either using methylamine and hydroxylamine-O-sulfonic acid or using ammonia and methylhydroxylamine-O-sulfonic acid. ... 

Formylation of the V-allyl indole derivatives 311 (obtained by allylation of the indole 310) afforded l-allyl-7-formyl-indole 312. Subsequent condensation of 7-formyl indole derivatives 312 with ethyl acetate in presence of sodium ethoxide gave 313 (89S322). Reaction of 312 with N-methylhydroxylamine hydrochloride afforded the cycloadduct, tetracyclic... 

The condensation products of 39 with hydroxylamine, O-methylhydroxylamine, malononitrile or dimethyl malonate have been formulated as 41 and 42.235... 

Methyl-4-hexenal, 59, 110 Methyl n-hexylcarbamate, 56,40 METHYL-2-HEXYNOATE, 55, 73 Methyl hydrazinocarboxylate, 58, 103 A-Methylhydroxylamine hydrochloride,... 

R = H, Scheme 27). On the other hand, reaction of 255a with N-methylhydrox-ylamine hydrochloride produces a mixture of two regioisomers 257 and 258 (R = Me). When the E-l(10)-unsaturated 5-oxo-5,10-secosteroid 255b was treated with hydroxylamine hydrochloride (R = H) or AT-methylhydroxylamine hydrochloride (R = Me), isoxazolidine 259 was formed regio- and stereoselec-tively in high yield via intramolecular 1,3-dipolar cycloaddition of the nitrone intermediate 256 (R = H or Me). 

The nitrone arising from reaction between (Z)-19-nor-5,10-secosteroidal ketone 260 a and M-methylhydroxylamine hydrochloride undergoes transannu-lar 1,3-dipolar cycloaddition to give isoxazolidines 261 and 262 and an aromatic derivative 263 originating from 261 (Scheme 28). Corresponding reaction of 260b produces two types of structurally different isoxazolidines 264 and 265 as well as the dienone 266. 

Silylation of hydroxylamine or N-alkyl or N-ethoxycarbonyUiydroxylamines is usually accomphshed, in 52-84% yield, by silylation with TCS 14/NEt3 [63, 161, 162]. Whereas the reaction of N,0-bis(trimethylsilyl)methylhydroxylamine 952 with aldehydes such as benzaldehyde, or with ketones, with to adducts such as 953, has already been mentioned at the beginning of Section 7.3 thermal and other reactions of N,0-bis(trimethylsilyl)hydroxylamine 1141 or N-substituted N,0-bis(trimethylsi-lyl)hydroxylamines 1121, 1128, 1131 are discussed in this section. 

Scheme 2.25 shows some examples of additions of enolate equivalents. A range of Lewis acid catalysts has been used in addition to TiCl4 and SnCl4. Entry 1 shows uses of a lanthanide catalyst. Entry 2 employs LiC104 as the catalyst. The reaction in Entry 3 includes a chiral auxiliary that controls the stereoselectivity the chiral auxiliary is released by a cyclization using (V-methylhydroxylamine. Entries 4 and 5 use the triphenylmethyl cation as a catalyst and Entries 6 and 7 use trimethylsilyl triflate and an enantioselective catalyst, respectively. 

Methylnitrat 1942 Epichlorhydrin 1955 1,4-Dioxan 1950 Methylhydroxylamin 1941 Propylenoxyd 1955, 1957 MW Ameisensauremethylcster 1959 MW... 

Chiacchio and co-workers <97T13855> reported a stereoselective synthesis of 133 via an intramolecular 1,3-dipolar cycloaddition. Intermediate 132 was generated in situ by the reaction of tra .v-/V-(2-formylphenyl)-i -methyl-2-phcnylcthenc- l -sulfonamide 131 with N-methylhydroxylamine and afforded a tricyclic benzothiazine 133 in 51% yield (Scheme 36). 

A similar but less useful amination reaction was reported by the Erdik group.426,427 They found that diarylzincs and trialrylzincates reacted with acetone 0-(2,4,6-trimethylphenylsulfonyl)oxime 327 and O-methylhydroxylamine in the presence of GuGN. The products of this reaction were hydrolyzed to afford the corresponding primary amines in modest yield (Scheme 167). 

When the aldehyde 137 and N-methylhydroxylamine (166) were mixed with silica gel and irradiated with microwaves for 15 min the adduct obtained was 168 (82% yield). A mixture of 137 and N-methylhydroxylamine (166) in alcohol, heated at 120°C in a sealed tube, afforded the products 168 and 169 in an 8 1 ratio (Scheme 9.51) [93], The authors proposed that the selectivity observed in the microwave-induced reaction results from a faster transformation leading to the kinetically controlled product. 

The action of iV-methylhydroxylamine on enantiopure 4-formylazetidin-2-ones bearing an N-tethered alkynyl group 89 has been studied and products formed by 1,3-dipolar cycloaddition and reverse Cope elimination isolated, e.g. 90 <00TL1647>. 

In carbonyl addition reactions, a commonly occurring and important mechanistic step is the transfer of a proton from one site to another in a reactive intermediate (proton switch). If the proton switch occurs sufficiently rapidly compared with the rate of collapse of the intermediate to reactants, the overall reaction may be facilitated by trapping of the unstable intermediate by the proton switch (Jencks, 1976). For example, in the formation of oximes from the reaction of benzaldehyde with O-methylhydroxylamine shown in (87H89) (Sayer and Jencks, 1973 Rosenberg et al., 1974), the first unstable intermediate (It) on the reaction pathway is converted by a proton switch (88) to the intermediate (I2) which has less tendency than It to... 

In order to study the mechanism of reverse Cope elimination reactions in the condensation of pentenal and hexenal with iV-methylhydroxylamine. it seemed reasonable to synthesize unsaturated nitrones (226). 

Recently a quantitative method for the determination of carbonyl groups in oxidized xylan has been developed.106 The method involves the reaction of the carbonyl group with O-methylhydroxylamine hydrochloride to form the corresponding oxime with the liberation of one mole of titratable acid. 

N-Methylhydroxylamine.—An aqueous solution of nitromethane is mixed with about its own weight of ammonium chloride, the mixture is then cooled (temperature about 10°) and three parts of zinc dust are added in small portions with constant shaking. Zinc dust is now removed by filtration, and it is found that the filtrate reduces ammoniacal silver and Fehling s solutions. The preparation of this easily accessible alkylhydroxylamine as hydrochloride is described by Beckmann, Annalen, 1909, 365, 204. 

---