Rearrangement nitroso group

As in other areas of the chemistry of nitroso compounds, the tacit assumption has been that the rearrangement of aliphatic nitroso compounds bearing hydrogens on the carbon atom which also carries the nitroso group rearranges to the oxime virtually instantaneously. Yet, recently, the existence of all types of aliphatic nitroso compounds has been well established. Without going into details here, nitrosomethane, nitrosocyclohexane, and nitrosodibenzoyl-methane have been prepared and appear to exist as reasonably stable dimers. 

F ritsch-Buttenberg-Wiechell — homoallyl — migration nitroso groups rearrangement position shift retroallyl rearrangement ring — santonin —... 

Migration of the Nitroso Group The Fischer-Hepp Rearrangement... 

There is indirect kinetic evidence that S-nitrosation of a sulphide occurs70, followed by a S to IV rearrangement of the nitroso group, leading finally to deamination (equation 31). The evidence is based on the much higher reaction rate when the sulphur atom is present. 

Rearrangement reactions involving the amino, nitro and nitroso groups... 

Typical primary amines which undergo such nitrosation are m-toluidine, p-xylidine, m-anisidine, 2-amino-4-methoxytoluene, 3-amino-4-methoxy-toluene, m-aminophenol, a-naphthylamine, l-naphthylamine-2-, -6-, -7-, and -8-monosulfonic acids, and l-naphthylamine-4-monosulfonic acid (which reacts with displacement of the sulfonic acid group). The secondary amines derived from these primary amines also can be nitrosated directly (i.e., without the intermediate formation of an JV-nitroso compound which needs to be subjected to the Fischer-Hepp rearrangement). The entering nitroso group appears to substitute exclusively in the para position. 

For a review of this and closely related reactions, see Morrison, in Feuer The Chemistry of the Nitro and Nitroso Groups, pt. 1 Wiley New York, 1969, pp. 165-213, 185-191. For a review of photochemical rearrangements of benzene derivatives, see Kaupp Angew. Chem. Int. Ed. Engl. 1980, 19, 243-275 [Angew. Chem. 92, 245-276). See also Yip Sharma Res. Chem. Intermed. 1989, 11, 109. 

The nitrosamines are neutral oily liquids of little importance in themselves. This reaction, however, serves to separate secondary bases from mixtures of primary, secondary and tertiary. The aromatic nitrosamines undergo an interesting rearrangement when heated with alcoholic hydrochloric acid (B., 20, 1247), the nitroso group migrating to a position in the nucleus, forming p-nitroso compounds. 

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