Nitrous oxide oxidative rearrangement

Rearrangement is also observed in the irradiation of Formula 450 which gives the hydroxamic acid (Formula 451) (203). This interesting rearrangement probably involves ring opening in the alkoxy radical (Formula 452) followed by recombination with nitrous oxide and cyclization (203). Oxidative fission of alkoxy radicals produced in nitrite... 

Therefore, intermediate IV may be safely postulated (see Scheme 9.1). When subjected to strong protic acid (HCl) the W-nitroso group of IV activates the C-N bond by providing an electron sink, which is a desirable component in the formation of carbenium ions. It is this carbocation that allows the Wag-ner-Meerwein rearrangement of the angular methyl that is illustrated in V. The more stable tertiary carbenium ion of VI is then ideally set up for the epoxide ring closure, following the departure of nitrous oxide from VI. 

Properties and reactions of nitramines Secondary nitramines are neutral, primary nitramines form salts with bases, but an excess of alkali often causes decomposition to the carbonyl compound, nitrogen, and water. Secondary nitramines and aqueous alkali afford nitrous acid, aldehyde, and primary amine. Acids decompose primary aliphatic nitramines with formation of nitrous oxide in a reaction that has not yet been clarified thus these compounds cannot be hydrolysed by acid to amines in the same way as nitrosamines, although, like the latter, they can be reduced to hydrazines. Primary and secondary aromatic nitramines readily rearrange to C-nitroarylamines in acid solution. Most nitramines decompose explosively when heated, but the lower aliphatic secondary nitramines can be distilled in a vacuum. 

The addition of ozone (O3) to alkenes to give a primary ozonide (molozonide), which rearranges to an ozonide and eventually leads, on reduction, to carbonyl compounds (aldehydes and/or ketones), has already been mentioned and the reaction itself is shown in Scheme 6.11. However, it is important to recognize that this is only one example of a 4th- 2n electrocyclic addition and that orbital overlap for many sets of these reactions dictates their courses as well. Thus, to show the similarity of some of these dipolar 3 -f 2 addition reactions Equations 6.53-6.56 are provided. Although any alkene might be used as an example, (Z)-2-butene is used in each to emphasize that aU of them occur with retention of stereochemistry and, in the first (Equation 6.53), the reaction with ozone to form the primary ozonide (molozonide) is presented again (i.e., see Scheme 6.11). In a similar way, with a suitable azide, R-N3, readily prepared from an alkyl halide (Chapter 7), the same alkene forms a triazoline (Equation 6.54) and with nitrous oxide (N2O) the heterocycle (Chapter 13) cis -4,5-dimethyl-A -l,2,3-oxadiazoline (ds-4,5-dihydro-4,5-dimethyl-l,2,3-oxadiazole) (Equation 6.55). Finally, with a nitrile oxide, such as the oxide derived from ethanenitrile (acetonitrile [CH3ON]), the same alkene yields a different heterocycle, the dihydroisoxazole, 3,4,5-trimethyl-4,5-dihydroisoxazole (Equation 6.56). 

In the traditional approach to s-caprolactam (Fig. 15.2), cyclohexanone reacts with hydroxylamine sulfate to obtain cyclohexanone oxime. The latter is then subjected to an oleum-catalyzed Beckmann rearrangement, affording the desired g-caprolactam. This complex approach is penalized by its complexity, the necessity to avoid emissions of nitrous oxides (NOx) and sulfur oxides (SOx), and mainly by... 

Usually, the cyclohexanone intermediate is made from the oxidation of cyclohexane. However, cyclohexanone is also made from phenol (Honeywell) or toluene (BASF, DSM). With the new processes, ammonia is oxidized to nitrous oxide (NjO), which is hydrogenated in the presence of sulfuric acid into hydroxylamine sulfate, which in turn is reacted with cyclohexanone to form cyclohexanone oxime. This chemical product is subjected to a Beckmann rearrangement with oleum to produce caprolactam. 

The formation of amidoazo-compounds by molecular rearrangement of diazoamido-compounds. The nitrous acid and nitric acid were oxidation products of the ammonia which was added. 

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