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Because of the peculiar charge distribution over the ring atoms, sydnone compouds are unstable and easily decomposed. This research focus on the acid fragmentation reaction of 3-aryl-4-acylsydnone. The research contents are divided into three subjects :
The first subject is to study the acid fragmentation reaction of 3-aryl -4-formylsydnone by the catalysis of hydrochloric acid. In the presence of hydrochloric acid in ethyl acetate at 60℃, 2-aryl-4-arylamino-2H-1,2,3-triazole is formed. This process involved the generation of aryl hydrazine from 3-aryl-4-formylsydnone which then reacted with 3-aryl-4-formylsydnone to produce arylhydrazone. Since arylhydra-zone is unstable, this compoud undergoes further fragmention and cyclization to give 2H-1,2,3-triazole.
The second subject deals with the acid fragmentation reaction of 3-aryl-4-acetylsydnone by the catalysis of hydrochloric acid. Only trace amount of 3-(p-chlorophenyl)-4-acetylsydnone could form two products. However 3-aryl-4-acetylsydnone arylhydrazone successfully undergoes acid fragmentation reaction. There are two possible ways to produce the same products: 3-aryl-4-acetylsydnone arylhydrazone are either undergo a series of fragmentation and cyclization to yield 2-aryl -4-arylammo-5-methyl-2H-1,2,3-triazoles or would be reacted with another arylhydrazine to form 1-aryl-4-arylazo-3-methyl-2-pyrazolin-5-ones.
The last subject is concerned with the acid fragmentation of 3-aryl -4-formylsydnone with acetyl chloride. 3-Aryl-4-formylsydnone was dissolved in acetyl chloride at 6~7℃, two α-substituted sydnonylal-dehyde arylhydrazone were obtained. A mechanism is proposed : 3-aryl-4-formylsydnone is partially converted into α-glyoxyloylarylhy-drazone. Which then further reacted with both 3-aryl-4-formylsydnone and acetyl chloride to give the two major products I and II in different ratio.
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