3-Arylsydnone-4-carbohydroximic acid chlorides 1 were reacted with hydrazine hydrate to give hydrazino(3-arylsydnon-4-yl)methanone oximes 2 which are good precursors of 4-triazolyl sydnones. 5-Aryl-3-(3-arylsydnon-4-yl)-1H-[1,2,4]triazoles 4 could be synthesized in excellent yields by reacting hydrazino(3-arylsydnon-4-yl)methanone oximes 2 with aromatic aldehydes 3 under acid catalysis. Compounds 2 were also reacted with 3-aryl-4-formylsydnones 5 and aliphatic aldehydes 7 to produce 3-(3-arylsydnon-4-yl)-5-(3-arylsydnon-4-yl)-1H-[1,2,4]triazoles 6 and 5-alkyl-3-(3-arylsydnon-4-yl)-1H-[1,2,4] triazoles 8, respectively.Many sydnone compounds are associated with pharmacological activities, such as antimicrobial, anti-inflammatory, analgesic and antipyretic properties, 1-6 and various substituted triazoles also exhibit biological properties and behavior. 7-12 Therefore, there exists a continuous interest in the syntheses of triazole derivatives. 13-18 Thus, synthesis of sydnones with a 1,2,4-triazolyl group substituted at a suitable position using a convenient method should be a significant aim for obtaining new biological active compounds. In the previous study, 3-arylsydnone-4-carbohydroximic acid chlorides 1, which were stable at room temperature were easily converted into 3-arylsydnone-4-carbonitrile oxides in polar solvent or basic aqueous solution. 19 The active nitrile oxides generated by this route could undergo cycloaddition with dipolarophiles to produce 4-heterocyclic sydnones. 20-25 3-Arylsydnone-4-carbohydroximic acid chlorides could also be used to react with some nucleophiles to give the precursors which were expected to cyclize with other reagents to yield the desired 4-heterocyclic sydnones. [25][26][27] The present work focuses on the syntheses of 5-aryl-3-(3-arylsydnon-4-yl)-1H-[1,2,4]triazoles 4. The corresponding hydrazino(3-arylsydnon-4-yl)methanone oximes 2 were first obtained through the reaction of starting materials 1 with hydrazine hydrate, and then compounds 2 were cyclized with various aromatic aldehydes 3 to give the desired products 4 under suitable acid catalyzing conditions.Although numerous aspects of 3-arylsydnone-4-carbohydroximic acid chlorides 1 have already been studied, and many 4-heterocyclic sydnones were synthesized, 22-26 the truly stereoisomeric structures of compounds 1 remained unknown until now. Generally, N-hydroxybenzimidomyl chloride contains two stereoisomers, with both E and Z forms existing simultaneously. In this study, compounds 1a-d synthesized as described in the literature 19 (Scheme 1) are exclusively Z-isomers based on the direct X-ray structure analyses of compounds 1a and 1b, and comparison of spectral data. Figures 1 and 2 display the molecular structures of compounds 1a and 1b. Scheme 1 1a: Ar = C 6 H 5 ; 1b: Ar = 4-CH 3 C 6 H 4 ; 1c: Ar = 4-CH 3 OC 6 H 4 ; 1d: Ar = 4-C 2 H 5 OC 6 H 4 Figure 1 Crystal structure of compound 1a Downloaded by: University of Florida. Copyrighted material.

3‐Arylsydnone‐4‐carbohydroximic acid chlorides (1) could react with sodium azide to produce the corresponding 3‐arylsydnone‐4‐carbazidoximes (2), but not 1‐hydroxytetrazoles 3. Treatment of 3‐arylsydnone‐4‐carbazidoximes (2) with acid chlorides such as acetyl chloride (4a), propionyl chloride (4b) and benzoyl chloride (4c) in the presence of excess triethylamine generated the derivatives of the azidoximes 5. To obtain the desired tetrazoles, the azidoximes 2 should first cyclize directly with acetyl chloride (4a) or propionyl chloride (4b) to afford the acetyl or propionyl derivatives 6. The cyclized tetrazole derivatives 6 underwent deacylation upon heating in ethanol to give 1‐hydroxy‐5‐(3‐arylsydnon‐4‐yl)tetrazoles (3).