Syntheses from other Heterocycles

摘要: It is important to be able aromatize imidazolines since a number of ring-synthetic procedures lead reduced imidazoles. 4-Aminoisoxazoles are sources α -acylaminoenaminones which cyclize with bases give 4-acylimidazoles. Oxazole-imidazole conversion has great importance, but it also implicated in some procedures, for example, the Bredereck method. Transformations benzofuroxans into 2-substituted benzimidazole N -oxides have synthetic importance. Although conversions other heterocyclic compounds benzimidazoles interest, there may value if reactions occur under neutral conditions (the usual cyclizations o -phenylenediamines acidic media). The chapter discusses imidazoles relation three- and five-membered rings. 2 H -Azirines or their salts converted when treated nitriles, process promoted by perchloric acid boron trifluoride etherate. Pyrazoles rearrange photochemical yields as high 30%. Frequently, however, mixtures isomers formed, decreasing utility approach.