| abstract |
New (di- or tetra-hydro)imidazo(2,1-b)thiazole cpds. have the formula: (where R1-4 are H, (substd.) alkyl, alkenyl, cycloalkyl, ar(alk)yl, halogen, NO2, CN, OH, SH, alkoxy, alkylmercapto, COOH, carboxylic ester, carbonamido or acyl. R1 and R4 together can form a bond. R2 and R3 together with the C atoms to which they are attached can form a (substd.) carbo- or hetero-cyclic ring). (I) are specified for use in photographic material for the Ag dye bleach process. They prevent undesirable bleaching adjacent to the exposed areas, so that colour pictures with purer tones and better contrast can be produced. |