7V-nitroso compounds

Some of the most important reactions of amines are brought about by nitrous acid (HONO). The character of the products depends very much on whether the amine is primary, secondary, or tertiary. In fact, nitrous acid is a useful reagent to determine whether a particular amine is primary, secondary, or tertiary. With primary amines nitrous acid results in evolution of nitrogen gas with secondary amines insoluble yellow liquids or solid 7V-nitroso compounds, R2N—N=0, separate tertiary alkanamines dissolve in and react with nitrous acid solutions without evolution of nitrogen, usually to give complex products ... 

In all the diazotization reactions discussed in Sections 2.1-2.4 an equimolar amount of water is formed as byproduct. There are two general pathways for obtaining diazonium salts without formation of water. One is based on the rearrangement of 7V-nitroso-7V-arylacetamides, the other on the nitrosation of a monoarylated sp2-hybridized nitrogen compound by nitrosating reagents XNO in which X is a weak nucleophile. 

AMJnsubstituted /3-lactams are nitrosated in acetic acid under nitrogen at 15 °C to give 7V-nitroso-/3-lactams (81), which can be reduced by zinc dust in acetic acid to afford the corresponding TV-amino compounds (82) (67G1719). 

Methylpyridine methiodide condenses with iV,7V-dimethyl-4-nitrosoaniline in the presence of piperidine to give the Schiff base (66 Scheme 53). The reaction fails with 2-methylpyridine itself but N-oxide analogues condense similarly (63JCS4600). 9-Methyl-acridine condenses with C-nitroso compounds to yield anils or nitrones. 

Similar to hydroxylamines, alkoxyamines may be oxidized to the nitroso compounds under loss of the alkyl group [165]. Radical cations or radicals obtained from 7V-alk-oxyamines may undergo intramolecular cyclization to double bonds like in pentenyl-alkoxyamines [26] or in 5-methoxyamino-5-methyl dibenzocycloheptene [166] [Eq. (33)]. 

Preparation of 7V-Labeled iV-Nitroso Compounds. The precursor urea, l,3-bis(2-chloroethyl) urea (la, BCU), was prepared in 40% yield by the method of Bestian (9). Its carbamate analog, N-chloroethyl-l-chloroethyl carbamate (2a), was prepared by the method of McQuinn et al. (10). Carbaryl (3a) was purchased from Aldrich Chemical Company (Milwaukee, WI) and was recrystallized from ethanol. 

Decomposition of diazo compounds to carbenes is a quite general reaction. Examples include the decomposition of diazomethane and other diazoalkanes, diazoalkenes, and diazo compounds with aryl and acyl substituents. The main restrictions on this method are limitations on the synthesis of the diazo compounds and their modest stability. The lower diazoalkenes are toxic and potentially explosive. They are usually prepared immediately before use. The most general synthetic route involves base-catalyzed decomposition of 7V-nitroso derivatives of amides or sulfonamides. These reactions are illustrated by several methods used for the preparation of diazomethane. 

Catechols and hydroquinones are oxidized to quinones (eq 5), and 7V-hydroxyureas are oxidized to nitroso compounds (eq 6). ... 

Aconine, the amino alcohol, is the parent of two ester-alkaloids, aconitine (the acetate benzoate) and jesaconitine (the acetate p-methoxybenzo-ate), and differs from mesaconine, the parent of mesaconitine (the acetate benzoate), only in the A-alkyl substituent. Aconine carries an 7V-ethyl (40, 49) and mesaconine an A-methyl group these two compounds thus yield the same nitro-AT-nitroso derivative, and aconitine and mesaconitine give the same oxidation product, oxonitine (41), with elimination of the A-alkyl group. It is convenient, therefore, to combine the discussion of these closely related alkaloids. 

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