Monoximes

It can act either as a nitrosophenol or as a quinone monoxime. Coloured derivatives, e.g. the sodium salt, are derived from the quinone form. Direct methylation gives a coloured compound which has been shown to be quino-nemethoxime OlCeH4tNOCH3 p-nitrosoani-sole CH30 C6H4 N0 has been obtained by another route and is colourless. 

Methyl ethyl ketone is allowed to react with n-butyl or iso-amyl nitrite in the presence of hydrochloric acid to yield diacetyl monoxime (nitrosomethyl ethyl ketone) ... 

The diacetyl monoxime condenses readily with hydroxylamine hydrochloride or sulphate with the formation of dimethylglyoxime (diacetyl dioxime) ... 

Monooximes of a-diketones have found applicability in the synthesis of 2-aminopyrazine 1-oxides by condensation with a-aminonitriles, and this reaction was used by White and coworkers in an approach to the synthesis of Cypridina etioluciferamine (Scheme 66 R = 3-indoloyl) (73T3761). In this instance, the use of TiCU as a catalyst was essential, since the carbonyl group in 3-acylindoles is normally deactivated and the required amine/carbonyl condensation is impractically slow. Under normal circumstances the carbonyl group in simple alkyl-substituted monoximes of a-diketones is the more reactive site and the reaction is rapid, requiring no catalysis (69LA(726)loo). 

Scheme 4 also represents the classical route to isoxazoles, first studied in 1888 by Claisen and his coworkers (1888CB1149). Reaction of a 1,3-diketone with hydroxylamine gives, via the isolable monoxime (108) and the 4-hydroxyisoxazole (109), the isoxazole (110). Unsym-metrical 1,3-diketones result in both possible isomers (110) and (111), but the ratio of the isomeric products can be controlled by the right combination of the 1,3-dicarbonyl component and the reaction conditions used. These important considerations are described in Chapter 4.16, along with the variations possible in the 1,3-dicarbonyl component designed to yield diverse substituents in the resultant isoxazole. 

In 1888 Claisen (1888CB1149) first recognized a general synthesis of isoxazoles (283) by the condensation-cyclization of 1,3-diketones (280) with hydroxylamine. It is now generally accepted that the monoxime (281) of the 1,3-diketone and the subsequent 5-hydroxy-isoxazoline (282) are the intermediate products of the reaction. The isolation of the monoxime (281) and 5-hydroxyisoxazoline (282), which were both readily converted into the isoxazole (283) by treatment with acid or base, has been reported (62HC(17)l). 

When the 1-monoximes or dioximes of 4-acetyl-l-tetralones are hydrogenated in the presence of palladium, mixtures of diastereoisomeric 1-aminotetralones are formed. The m-aminoketone isomers readily form dehydrobenzoisoquinuclideines (3,4-disubstituted-1,4-dihydro-1,4-ethano-isoquinolines). Quaternary immonium salts prepared from these bicyclic imines are then converted by bases to bicyclic enamines [2,4-disubstituted-3-alkylidene-1,4-ethano-1,2,3,4-tetrahydroisoquinolines (25)]. 

Diacetonamine hydrogen oxalate, 14,85 Diacetone alcohol, 10, no Diacetyl monoxime, 10, 22 Diallylcyanamide, 10, no Diaminodurene, 10, 41... 

Nitroso-1-Naphthol (Naphthochinon-(l,4)-monoxime). ON.CioHg.OH, mw 173.18, N 8.09%, OB to C02 —198.64%, pale yellow needles from benz or dil ale, mp 193—94° (decompn at 190° thru mp). Sol in ale, me ale, acet, eth, chlf C disulfide. Prepn from 4-nitroso-1-methoxy-naphthalene by saponification with mineral acid. 1166.4cal/g-mole q 1166.5 cal/g-mole... 

An analogous approach starting from monoximes 44 derived from 1,2 diketo derivatives was described in 2004 [44]. Reaction with different aldehydes in the presence of NH4OAC in acetic acid at 200 °C under microwave irradiation for 20 min gave the corresponding trisubstituted imidazoles 45... 

P-Benzilmonoxime. Boil 10 g. of the pure a-monoxime for 15 minutes with 1 g. of dried animal charcoal in a quantity of pure benzene just sufficient to dissolve the a-monoxime at the boiling point. Filter off the charcoal and allow the filtrate to stand. The p-monoxime -f 0-5 CgH, crystallises slowly on cooling a further crop can be obtained by evapora tion of the mother liquid. An excellent yield of the p-monoxime, m.p. 112°, is obtained. The pure S-oxime causes no colour change with aqueous - alcoholic copper acetate solution if it is contaminated with the a-oxinie, a greenisli colour is produced. 

Prompted by the dissociation of imidazole-iV-carboxamides into isocyanates, the preparation of alkoxyisocyanates (i.e. representatives of the hitherto unknown monoximes of carbon dioxide) was attempted. 141 151 However, when JV-benzyloxycarba-moylimidazole (ImCONHOCH2C6H5) was heated, the corresponding trialk-oxyisocyanuric acid was formed by trimerization of OCNOR. 141... 

The base was being prepared by distilling a mixture of hydroxylamine hydrochloride and sodium hydroxide in methanol under reduced pressure, and a violent explosion occurred towards the end of distillation [1], probably owing to an increase in pressure above 53 mbar. It explodes when heated under atmospheric pressure [2], Traces of hydroxylamine remaining after reaction with acetonitrile to form acetamide oxime caused an explosion during evaporation of solvent. Traces can be removed by treatment with diacetyl monoxime and ammoniacal nickel sulfate, forming nickel dimethylglyoxime [3], An account of an extremely violent explosion towards the end of vacuum distillation had been published previously [4], Anhydrous hydroxylamine is usually stored at 10°C to prevent internal oxidation-reduction reactions which occur at ambient temperature [5], See other REDOX REACTIONS... 

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