Biaryl sulfonamides from O-acetyl amidoximes: 1,2,4-Oxadiazole cyclization under acidic conditions

摘要

A series of 4-cyanobenzenesulfonamides (1a-h) was converted to the corresponding O-acetylated amidoximes (2a-h). The reaction of 1a was exemplarily investigated with respect to the formation of a byproduct, which was identified as 1,2,4-oxadiazole derivative 3a. This observation led to the development of an improved procedure for the preparation of 2a-h. Compounds 2 could be transformed to 1,2,4-oxadiazoles 3a-h in high yields and purity upon heating in acetic acid.