FIELD: organic chemistry, agriculture. SUBSTANCE: invention describes the novel derivatives of 2-cyano-1,3-dione of the formula (I): 
where R means cycloalkyl-group containing from 3 to 6 carbon atoms; R1 means hydrogen atom or direct or branched alkyl-group containing up to 6 carbon atoms that is substituted with the group -OR5 where R5 means direct or branched alkyl-group containing up to 6 carbon atoms that is optionally substituted with one or some halogen atoms being the latter can be similar or different; or R1 means the group taken among R5, nitro-group, -S(O)R5,-OR5; R2 means halogen or hydrogen atom or the group taken among -OR5,-S(O)R5; R3 means hydrogen atom; R4 means direct or branched alkyl-group containing up to 6 carbon atoms; n = 0, 1 or 2; p = 0; q = 0; or its agriculturally acceptable salt showing herbicide activity. Invention describes also method of their synthesis, herbicide composition and method of weed suppression. EFFECT: enhanced effectiveness of herbicide composition as compared with known one. 11 cl, 32 ex
