Ring-ring interconversions.: Part 2.: Effect of the substituent on the rearrangement of 6-aryl-3-methyl-5-nitrosoimidazo[2,1-b][1,3]thiazoles into 8-aryl-8-hydroxy-5-methyl-8H-[1,4]thiazino[3,4-c][1,2,4]oxadiazol-3-ones.: A novel class of potential antitumor agents

The reaction of several 6-aryl-3-methyl-5-nitrosoimidazo[2,1-b][1,3]thiazoles with hydrochloric acid by refluxing in ethanol gives new 8-aryl-8-hydroxy-5-methyl-8H-[1,4]thiazino[3,4-c] [1,2,4]oxadiazol-3-ones for testing of their biological activity. By carrying out the reaction at room temperature it has been possible to isolate reaction intermediates to which structures have been assigned. This study has provided information on the reaction mechanism and on the effect of the substituent in the phenyl ring on the yield of the reaction. (C) 1999 Elsevier Science Ltd. All rights reserved.