2,4-Dichloro-5-thiazolecarboxaldehyde and a process for its preparation

The new 2,4-dichloro-5-thiazolecarboxaldehyde of the formula can be prepared in good yields by reacting 2,4-thiazolidinedione (III) with 1-1.5 mol of dimethylformamide and 3-10 mol of phosphorus oxychloride at the reflux temperature of the reaction mixture (about 115 DEG C.) until evolution of HCl gas has ended, and then working up hydrolytically. The aldehyde (II) can readily be converted, via the new oxime (IV), into the corresponding nitrile, 2,4-dichloro-5-cyanothiazole (V), which is a known intermediate for the preparation of herbicidal active compounds of the thiazolyloxyacetamide type.