Fischer-Hepp

Fischer-Hepp rearrangement The nitros-amines of aromatic secondary amines when treated with hydrochloric acid give nuclear substituted nitrosoamines. Among the benzene derivatives, if the para position is free the -NO group displaces the hydrogen atom there in naphthalene derivatives it enters the 1-position ... 

Dibenz[6,/]azepine, 10,11-dihydro-N-nitroso-Fischer-Hepp rearrangement, 7, 527 Dibenz[6,/]azepine, 10,11-ethoxyring opening, 7, 526 Dibenz[6,/]azepine, N-nitroso-synthesis, 7, 527... 

FISCHER - HEPP Nilrosamine Rearrangemenls Rearrangement ol N-nitroso lo C-nitroso denvalives... 

Nitroso-5//-dibenz[/>,/]azepine (9, R = NO) is relatively stable to photolysis under argon, whereas in benzene solution in the presence of oxygen, irradiation induces an oxidative Fischer -Hepp-type rearrangement to 2-nitro-5//-dibenz[6,/]azepinc (10, R = N02), accompanied by ring contraction to acridine-9-carbaldehyde184 (see also Section 3.2.2.4.). 

We mention Williams work briefly here because it may also explain Blangey s observations strongly basic primary amines unequivocally form 7V-nitrosoanilinium ions in strongly acidic media. In contrast to the rate-limiting deprotonations of the less basic aromatic and heteroaromatic nitrosoamine cations discussed in this section, the TV-nitroso cation of a strongly basic amine deprotonates extremely slowly. Therefore, the nitroso rearrangement, the Fischer-Hepp reaction, competes effectively with the 7V-deprotonation. 

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

Rearrangement of N-nitroso aromatic amines (Fischer-Hepp)... 

The Fischer-Hepp rearrangement generally gives only the 4-isomer and, apart from examples in the naphthyl series, the 2-isomer has rarely been identified. Now the 2-isomer has been characterized96 as the minor product from the reaction of the diphenylamine derivative 96. The 2-nitroso product gives the cyclized product 97 on treatment with hydrogen peroxide (Scheme 17). 

Quite different from the Fischer-Hepp rearrangement is the reaction of N-nitrosodehydromorpholine 98 which, in methylene chloride containing HC1, gives at room temperature l-azo-4-oxa-3-oximinocyclohexene 99, which ring-opens on treatment... 

Fischer-Hepp rearrangement, 22 151 Fischer-Tropsch catalysis, by graphite intercalation compounds, 23 318 Fish, arsenic in, 44 150, 167, 168, 170, 180 Fission... 

One of the best-knbwn methods for the preparation of aromatic nitroso compounds is the Fischer-Hepp rearrangement of A-nitrosoamines (Eq. 2). In effect, this reaction is the C-nitrosation of secondary aromatic amines. 

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