HETEROCYCLIC COMPOUNDS

A herbicidal compound of formula (I): in which the dotted line indicates the presence of two double bonds arranged so as to form a fused hetro-aromatic ring system; Py is an optionally substituted pyrazole ring; W is O or NR ; where R is hydrogen or lower alkyl; X is (CH2)n, CH=CH, CH(OR )CH2, COCH2; where n is O, 1 or 2; R and R are independently selected from H, optionally substituted alkyl, alkenyl or alkynyl, halogen, NR R , or R and R together with the carbon to which they are attached form an optionally substituted alkenyl or cycloalkyl group; R is CO2R , CN, COR , CH2OR , CH(OH)R , CH(OR )R , CSNH2, COSR , CSOR , CONHSO2R , CONR R , CONHNR R , CONHNR R R R , CO2R or COON=CR R ; R is an agriculturally acceptable cation and R is an agriculturally acceptable anion. R , R and R are independently selected from H or an optionally substituted alkyl, aryl, alkenyl or alkynyl group; R , R , R , R and R are independently selected from H or an optionally substituted alkyl, alkenyl, aryl or alkynyl group; or any two of R , R , R , R and R together with the atom to which they are attached form a cycloalkyl or heterocyclic ring. Processes for the preparation of these compounds and compositions containing them are also described.