Amines unsymmetrical hydroxylamines

As an alternative to an olefination method, the Cope elimination can be used as a preparative method for unsymmetrical hydroxylamines. Addition of unsymmetrical secondary amine 41 to a,p-unsaturated compounds gave access to compound 42, which underwent oxidation and Cope elimination to yield the unsymmetrical hydroxylamine product 44.16... 

Another aspect to Rogers s work on the synthesis of unsymmetrical hydroxylamines (Section 4.2.5.1) is that the elimination step is base catalyzed (occurring at room temperature).16 Salts of amine oxides derived from P-aminopropionic esters 45 or nitriles 46 undergo the reaction, which involves a retro-Michael addition, facilitated by the formal positive charge on nitrogen. 

A convenient synthetic procedure for the preparation of azo compounds, particularly unsymmetrically substituted ones, involves the reaction of aromatic nitroso compounds with aromatic amines [31a, b]. The reaction is of particular interest because the replacement of the amine by the corresponding hydroxylamine leads to the formation of the related azoxy compounds (see Chapter 15, Azoxy Compounds ). 

A very flexible method of preparing unsymmetrical azo compounds makes use of the condensation of C-nitroso compounds with amines. Thionylamines have also been condensed with substituted hydroxylamines to produce azo compounds not usually accessible by other means. Treatment of dialkylsulfuric diamides with sodium hypochlorite is one means of preparing aliphatic azo compounds. Aromatic amines and aromatic nitro compounds at high temperature produce azo compounds. 

A coupling procedure particularly suited to the synthesis of unsymmetrical diacetylenes involves the reaction of a terminal acetylene with a 1-bromo-acetylene in the presence of a catalyst consisting of a solution of copper(i) chloride in a primary amine to which small quantities of hydroxylamine hydrochloride is added (the Cadiot-Chodkiewicz coupling). 

Secondary amines give only a monosubstituted product. Both of these reactions are thermally reversible. The product with ammonia (3,3, 3"-nitrilotrispropionamide [2664-61-1] C9HlgN403) (5) is frequently found in crystalline acrylamide as a minor impurity and affects the free-radical polymerization. An extensive study (8) has determined the structural requirements of the amines to form thermally reversible products. Unsymmetrical dialkyl hydrazines add through the unsubstituted nitrogen in basic medium and through the substituted nitrogen in acidic medium (9)). AlonoalkyHiydroxylamine hydrochlorides react with preservation of the hydroxylamine structure (10). Primary nitramines combine in such a way as to keep the nitramine structure intact. 

Unsymmetrically substituted 1,3-diynes can be obtained via the Cadiot-Chodkiewicz copper(I)-catalyzed coupling of 1-alkynes with 1-halo-l-alkynes in the presence of hydroxylamine hydrochloride and an amine. ... 

The crude product obtained was purified by column chromatography over silica gel with 1 1 ethyl acetate-hexane as the eluant to secure the final compound (229) in 55% yield. Careful isolahon and characterization showed that one of the major by-products of this reaction to be the bisurea derivative (259) in yields of up to 20%. We explored phe-nylchloroformate as a substitute to triphosgene in the preparation of unsymmetrical urea derivatives. Phenylchloroformate (260) in the presence of an appropriate base on reaction with an amine (241) gave the corresponding carbamate, which on further reaction with A-methyl hydroxylamine gave a urea derivative (229). However, the formation of bisurea... 

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