Thiazolotriazole herbicides

The invention provides certain herbicidal thiazolotriazole sulphonamides, processes for their preparation, and compositions containing them, the compounds being of the formula: where: R' and R2, which may be the same or different, each represent hydrogen, hydroxy, halo, cyano, substituted or unsubstituted alkyl, alkoxy, alkenyloxy, alkynyloxy, aryl, aralkyl, heteroaryl or carbamoyl, or a group -COR8 or -CO2Ra or where R8 is hydrogen or alkyl: or R1 and R2 together represent an alkylene chain of 3 or 4 carbon atoms:R3 represents a substituted or unsubstituted aryl, heterocyclyl or benzheterocyclyl group; andR4 represents hydrogen, an alkali-metal atom, an ammonium group, a substituted or unsubstituted alkyl, alkenyl, alkynyl, acyl, alkoxycarbonyl or aralkyl group, a heterocyclic group, or a group of the formula: where R1 and R2 are as defined hereinbefore.