Nitrosoamides, decomposition

DEAMINATION OF AMINES. 2-PHENYLETHYL BENZOATE VIA THE NITROSOAMIDE DECOMPOSITION... 

In general, the nitrosoamide decomposition proceeds with retention of configuration6i 0... 

A similar trend has been observed for the closely related, N-nitrosoamide decomposition see Ref. 23. 

Table 7. Intramolecular and intermolecular products in the nitrosoamide decomposition in acetic acid.

If, after the nitrogen molecule has been ejected, the p orbital of the cation and the counter ion are not aligned for orbital overlap, some rotation of the cation will be required for bonding. In some cases, sufficient rotation will occur so that bond formation can occur on what was the back side of the cation thus the intramolecular inversion observed in the nitrosoamide decomposition and the nitrous add deamination can be accounted for at this stage in the reaction. This interpretation also accounts for the fact that in the acetic acid decomposition of the tolyltriazene of 1-phenylethylamine, the reaction of the cation with tolylamine proceeds with more retention of configuration than the reaction of the cation with the add anion that is, the position of the counter ion with respect to the cation determines the overall stereospecificity (section b). 

Path d) retention of corfguration. Alcohols are formed in low yield in the nitrous acid deamination of amines in acetic acid, and they have been isolated in only a few instances. The alcohol represents the intramolecular product of the deamination and with the exception of the norbomanols, which will be discussed later, they are formed from secondary and tertiary carbinamines with overall retention of configuration (Table 12). The results are so striking and so similar to those of the nitrosoamide decomposition (Tables 6 and 7) that we feel a common reaction mechanism must be involved. Paths (d) and (g) (equation 146) involving predominant collapse on the front side of the cation are proposed for the formation of the alcohoP° -i3i-i °. 

Front-side exchange (path (e)) partakes of the character of an add-base reaction in the nitrosoamide decomposition (section a (2) (e)), and in view of the basicity of the incipient hydroxide ion, one would expect extensive exchange of the counter ion in the nitrous add deamination (equation 146, path (e)). In fact, acetate esters are the chief products from deaminations in acetic add (ref. of Table 12), and the alcohol component of the reaction has only rarely been reported (Table 12). In acetic acid runs, the adds present in the medium (HX, equation 146) are HO2CCH3, HONO and HONO2 (the latter from the disproportionation of nitrous add). Acetate esters have invariably been reported as products in deamination and in a few instances nitrite and nitrate estershave been isolated. 

The relationship of the nitrous acid and nitrosoamide methods of deamination is more tenuous in water since only one example of the i nitrosoamide decomposition in aqueous media has been reported. The decomposition of A -nitroso-A -n-propylbenzamide in dimethyl-formamide-water (60/40 by vol) yielded a propyl benzoate fraction containing 9% of the isopropyl isomer and a propanol fraction con- taining 33% of isopropyl alcohoP . The nitrous acid deamination of n-propylamine under the same conditions yielded an alcohol fraction containing 31% of isopropyl alcohoP. The similarity in the isomer contents of the alcohol portions suggests that common intermediates were involved. The less extensive isomerization of the benzoates may be a reflection of the shorter lifetime of the propyl cations trapped by negatively charged coimter ions compared to those trapped by neutral solvent molecules on the other hand, the role of diazopropane must be determined before definitive conclusions are possible. 

The known free-radical decomposition of aryl nitrosoamides (ArN(NO)COR ) and the report that nitrosoamides of 0-alkyl-hydroxylamines decompose by a free-radical pathway indicate that free-radical processes might occur in the normal nitrosoamide decomposition. In fact, the aliphatic nitrosoamides have been used as initiators at elevated temperatures for the polymerization of styrene and other olefins At, or near, room temperature, however, it appears that free radicals are not formed in the nitrosoamide decomposition. It has been found, for example, that (1) COj (a product of the decarboxylation of carboxyl radicals) is not formed in the decomposition (2) the scavenger nitric oxide has no effect on the reaction (3) normal products and no polymer are formed in the decomposition of A -(i-butyl)-A -nitrosobenzamide ° ° and N-nitroso-7V-(l-phenylethyl)acetamide -in styrene and (4) no difference in acetate yields is observed when A -nitroso-A-(1-phenyl-ethyl) acetamide is decomposed in benzene in the presence or absence of 0-1 m Styrene and 1-phenylethyl acetate react with... 

Finally, the mechanism outlined in equation (133) can account for other observations on the non-concertedness of the nitrosoamide decomposition and related reactions. For example, although the solvolysis of acetate yields only tram-diacetate, presumably via 46 formed by a neighboring group interaction (equation 136) , the nitrosoanude decomposition on an... 

As in the nitrosoamide decomposition, the yields are satisfactory for primary carbinamines and moderate for secondaiy carbinamines (Table 10). The decrease in yields in the latter case is largely the... 

The reaction of nitrosyl chloride with n-butylamine in methylene dichloride yields n-butyl chloride free of isomers and the reaction with 1-phenylethylamine in dioxane yields 1-phenylethyl chloride with overall retention of configuration . These results are similar to those obtained in the nitrosoamide decomposition in non-polar solvents, and a similarity in mechanisms seems certain. The reaction of nitrosyl chloride with various amines at —75° in methylene dichloride was shown to yield both the alcohol and the chloride (Table 14). 1-Phenylethylamine yielded a larger fraction of alcohol than did... 

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