Abstract: Compounds of the formula: ##STR1## wherein R.sub.1 and R.sub.2 each independently represents hydrogen, optionally substituted alkyl, aryl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, aralkyl, alkaryl, hydroxy, alkoxy, alkenyloxy, alkynyloxy, alkylcarbonyl, alkoxycarbonyl, amino, mono- or dialkylamino, alkoxycarbonylamino, optionally substituted heterocycle or arylamino, dialkylcarbamoyl, trialkylsilyl or fused ring structure, or together form an alkenylene chain or an alkylene chain which is optionally interrupted by oxygen or sulphur or --NR--, R being hydrogen or alkyl; R.sub.3 represents hydrogen or halogen, or optionally substituted alkyl, alkoxy, aryl or aryloxy, or cyano, carboxy, alkoxycarbonyl, (alkylthio) carbonyl, alkylcarbonyl, amido, alkylamido, nitro, alkenyloxy, alkynloxy, alkylthio, haloalkylthio, alkenylthio, alkynylthio, alkylsulphinyl, alkylsulphonyl, alkyloximinoalkyl or alkenyloximinoalkyl; R.sub.

Abstract: Compounds of formula I ##STR1## are useful as herbicides, effective against dicotyledonous weeds.