1- Phenyl-4-formyl-l,2,3-triazole

In 1944, Hann and Hudson found that, when refluxed with cupric sulfate, osazones are converted into colorless triazole derivatives which they designated osotriazoles. They determined the structure of the d-orahmo-hexulose derivative by means of the following reactions (1) it gave a tetraacetate and a tetrabenzoate which could be saponified to the parent osotriazole, indicating the presence of four free hydroxyl groups therein (2) on periodate oxidation, 3 moles of oxidant were consumed per mole of (71), giving 1 mole of formaldehyde, 2 moles of formic acid, and a known compound, 4-formyl-2-phenyl-l, 2,3-triazole (72). 

The sugar residues in osotriazoles can be readily acetylated, benzoylated (see Table II, p. 117), or p-toluenesulfonated. Further, as previously stated, osotriazoles can be oxidized with sodium periodate or red lead to give 4-formyl-2-phenyl-l,2,3-triazole (3), or with 20% nitric acid, aqueous potassium permanganate, or ceric sulfate to give 2-phenyl-l,2,3-triazole-4-carboxylic acid (5). 

Interesting synthetic applications of these degenerate rearrangements are the preparation of l-alkyl-4-formyl-l,2,3-triazole 110 from l-phenyl-4-... 

Uber eine Relais-Synthese lassen sich aus 4-(a-Amino-benzy]idenamino)-4H-l,2,4-triazolcn mit Carbonsaureanhydriden oder Carbonsaure-chloriden in Dimethylformamid 2-substi-tuierte 1,3,4-Oxadiazole im Eintopfverfahren herstellen552,553. Diese Reaktion verlauft iiber Acyl-hydrazone von 1-Formyl-3-phenyl-l,2,4-triazol, dessen Pyrolyse ebenfalls gute Aus-beuten liefert552. Mit dieser Methode konnten einige 1,3,4-Oxadiazole in besseren Ausbeuten und groBerer Reinheit als nach anderen Verfahren synthetisiert werden. 

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