Transformations of heterocycles into tetrazoles as well as conversions of the latter into other rings are reviewed. The literature is covered through early 1998 (material that has been surveyed by Van der Plas [1] and Benson [2] is resumed in abridged fashion). From the wide variety of interconversions accumulated in this overview a great many processes emerge that are of prime importance preparatively; moreover, quite a number of reactions will arouse interest in their mechanisms.

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Hydroxylamin und seine N‐ und/oder O‐Alkylderivate lassen sich im sauren wäßrig‐alkoholischen Medium nach dem Syntheseprinzip der Vierkomponenten‐Kondensation (Ugi‐Reaktion) mit Aldehyden und Isocyaniden zu α‐Hydroxylamino‐carbonsäureamiden (4, 6, 8) (bzw. mit N‐Isocyan‐dialkylaminen zu α‐Hydroxylamino‐carbonsäurehydraziden 13) umsetzen. Aus Hydroxylaminen mit freier H2N‐Gruppe erhält man in bestimmten Fällen fast ausschließlich Produkte einer „doppelten”︁ Ugi‐Reaktion (9, 14).

For Abstract see ChemInform Abstract in Full Text.

Eingegangen a m 14. Marz 1974Auf Hydroxylamine wird die Tetrazol-Variante der Titelreaktion angewandt ; bei Vorliegen freier NH2-Gruppen tritt doppelte Umsetzung ein, wahrend stlrkere sterische Hinderung lediglich zur Bildung entsprechender (Hydroxyalky1)tetrazole fiihrt. Einige Produkte werden als Acylderivate charakterisiert, von denen ein Teil bei relativ niedriger Temperatur einer Seitenketten-Pyrolyse unterliegt. Hydroxylamines in the Four-Component Condensation (Vgi Reaction), II 1)Hydroxylamines undergo the title reaction in the presence of hydraroic acid to give the expected I ,S-disubstituted tetrazoles. In the case of an unsubstituted NH;! group a N,N-disubstituted reaction product is obtained, whereas in the case of severe steric hindrance the corresponding (hydroxyalky1)tetrazole is formed. A few of the tetrazoles obtained were converted to acyl derivatives, some of which are susceptible to side-chain pyrolysis under relatively mild conditions.

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3a,6‐Dihydro‐3H‐imidazo[1,2‐d]tetrazoles from 1‐ and 4‐Phenacyl‐1H‐tetrazolium Salts and Ammonia Treatment of the tetrazolium salts 1 with aqueous ammonia affords the novel ring system 2 (in certain cases along with the ylides 3). The structure of 2 has been confirmed by an X‐ray analysis of 2a.

No abstract