Compounds of formula (I) wherein R1-R4 and W are as defined in the description and the agrochemically acceptable salts and tautomers, enantiomers and stereoisomers of such compounds of formula are suitable for use as herbicides.
Mutterer,F.; Weis,C.D., Journal of Heterocyclic Chemistry, 1976, vol. 13, p. 1103 - 1104