The bromination of 4-chloro-3-sulfamoyl acetophenone (I) with Br2 in ethyl acetate gives 4-chloro-3-sulfamoyl-alpha-bromoacetophenone (II), which is cyclized with N,N'-dimethylthiourea (III) in acetone and finally treated with NaHCO3 in water.
The bromination of 4-chloro-3-chlorosulfonylacetophenone (IV) with Br2 in ethyl acetate yields 4-chloro-3-chlorosulfonyl-alpha-bromoacetophenone (V), which is cyclized with N,N'-dimethylthiourea (III) affording 4-(4-chloro-3-chlorosulfonylphenyl)-3-methyl-2-(methylimino)-1,3-thiazolidin-4-ol (VI). Finally, this compound is treated with NH3 in methanol.
The reaction of 4-chloro-3-sulfamoyldiazoacetophenone (VII) with HCl in diglyme yields 4alpha-dichloro-3-sulfamoylacetophenone (VIII), which is cyclized with N,N'-dimethylthiourea (III) in acetone. Compound (VIII) can also be obtained by reaction of 4-chloro-3-sulfamoyl-alpha-hydroxyacetophenone (IX) with refluxing SOCl2.