A Modified Procedure for the Synthesis of 5-Amino-3-arylisoxazoles and Their Reactions with Tetrasulfur Tetranitride Antimony(V) Chloride Complex (S4N4ÅESbCl5) : Novel Synthesis of 3-Aryl-1,2,5-thiadiazole-4-carboxamides

Dropwise addition of a-bromo ketoximes to a solution of KCN in MeOH at room temperature gave 5-amino-3-arylisoxazoles in moderate to good yields.Treatment of the isoxazoles prepared with tetrasulfur tetranitride antimony (V) chloride complex (S 4 N 4 •SbCl 5 ) in toluene at 100°C afforded novel 3-aryl-1,2,5-thiadiazole-4-carboxamides.Isoxazoles are an important class of heterocyclic compounds and their chemistry has been extensively studied. 1 Recently we have shown that treatment of 3-alkyl-5-aryl-and 3,5-diarylisoxazoles (1) with tetrasulfur tetranitride antimony(V) chloride complex (S 4 N 4 •SbCl 5 ) (2) in toluene at reflux gave 3-alkyl-4aroyl-and 3-aroyl-4-aryl-1,2,5-thiadiazoles (3), 2 whereas compounds (1) did not react with tetrasulfur tetranitride (S 4 N 4 ) (4) under the same conditions with quantitative recovery of 1 (Scheme 1).