1.2.4- Triazole, 1-halo-, rearrangement

Rearrangement of acyl and halo groups are the most common reactions of nitrogen substituents of triazoles. 

Rearrangement of acyl and halo groups are the most common reactions of triazoles with functions on nitrogen. The chemistry of 4-hydroxytriazoles , in effect Af-oxides, has been less extensively studied than that of triazolinones. The N—O bond is cleaved by phosphorus halides and acidic anhydride but not by oxidation with permanganate or by alkaline bromination (70jpr610). 

For 1,2,4-triazoles, all the A-halo derivatives are relatively stable. Their stability is determined mainly by possibile rearrangement to C-halotria-zoles and dissociation to the starting materials (67ZC184 72JPR923 90IZV2814). 

In contrast to other azoles whose stability decreases from A-iodo to A-bromo and further to A-chloro derivatives, l-chloro-3-nitro-l,2,4-triazoles are more stable that their 1-bromo and 1-iodo analogs. In this series the stability order is reversed (96UP1). Rearrangement of A-halo-1,2,4-triazoles is described in Section IV,B,2. 

Rearrangement of V-halo-l,2,4-triazoles to C-haloderivatives is described in a series of reports. The possibility of formation of C-halo-1,2,4-triazoles depends on the reactions conditions on the nature of the halogen and on the presence, type, and location of substituents at the carbon atoms of the ring. 

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