Position Isomerism in the Azoxybenzenes

o-Nitrobenzylidene compounds. Part 3. Formation of 4-arylamino-3-methoxycinnoline 1-oxides from N-o-nitrobenzylideneanilines, cyanide ion, methanol: the intermediacy of 2-aryl-3-cyano-2H-indazole 1-oxides

“…It is thus a reasonable starting hypothesis that those cyclisations which produce no indazole are those in which the initial formation of the indazole oxide is suppressed. Most of the anils which show this reaction behaviour are derived from orthosubstituted amines, an observation which gives support to the idea that steric effects may be important in inhibiting the cyclisation (7) (8) and thus permitting the alternative mode of cyclisation to the cinnoline oxides (10). It is significant in this connection that previous workerss have failed to obtain indazole oxides of the type (8) from the o-nitrobenzylidene derivatives of ortho substituted amines, and significant also that the only such anil from which we have even detected an indazole is (7i), in which the ortho substituent (fluoro-) is small.…”

“…(ii) o-Ffuoro-N-o-nitrobenzyfideneanifine (7i). If, as previously suggested, ortho substituents in the amine-derived ring of the anils (7) sterically hinder the formation of indazole oxides (S), then the smaller this ortho substituent, the better the chance of this type of cyclisation. The reactions of the o-fluoroanil (7i) support this suggestion.…”

“…It is thus clear that the formation of 4-arylamino-3-methoxy- (7).-All the anils except (7g) and (71) were prepared by dissolving equimolar quantities of o-nitrobenzaldehyde and the appropriate amine in the minimum volume of warm ethanol, boiling the solution for ca. 5 min, and cooling in ice-water.…”

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The N-o-nitrobenzylidene derivatives of variously substituted anilines (7) have been cyclised by potassium cyanide in methanol, to give 4-arylamino-3-methoxycinnoline 1 -oxides (9), the structures of which have been confirmed by independent synthesis of one representative [thep-toluidino-compound. (9b)l. These cinnoline oxides are the main products (sometimes the only isolated products) when the amine-derived ring in ( 7) is ortho-substituted; in other cases the cinnoline oxides are minor products formed along with 2-aryl-3-cyano-2H-indazoles (10).

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Azoxy Compounds

“…(29) [34]. This required assumptions about directing influences which were difficult to sub stantiate.…”