Synthesis of thieno[2,3-d]thiazole-6-carboxylic acid derivatives as potential inducers of systemic resistance in plants

Reduction of nitrothiocyanatothiophene 2, available via nucleophilic substi tution from the corresponding bromo compound 1, gave thienothiazole 3 in ex cellent yield. Conversion of the amino functionality under Sandmeyer condit ions gave access to halo compounds 4 as key intermediates for the subsequen t introduction of sulfur, nitrogen, and oxygen nucleophiles. An unexpected side-reaction was observed when DMF was used as solvent and a mechanism for the introduction of a dimethylamino group is proposed.