Compounds of the formula (I) and their salts as defined in claim 1, in which R1 is CO—Q—R8, where R8=H or R R2 and R3 are H or (C1-C4)alkyl, R4 is H, R, RO, OH, RCO, RSO2, PhSO2 R5 is RSO2, PhSO2, PhCO, RNHSO2, R2NSO2, RCO, CHO, COCOR′, CW—T—R9, CW—NR10R11, CW—N(R12)2 or R4 and R5 together are the chain (CH2)mB or —B1—(CH2)m1B— where B=SO2, m=3, 4; m1=2, 3; T and W=O, S; Q=O, S, NR13 where R13=H, R; R6=H, R, RO, RCO, ROCO, Hal, NO2, CN; R7=H, CH3; R9=R; R10, R11=H, R; N(R12)2=heterocycle A=pyrimidinyl and triazinyl radical or an analog thereof, where R=(substituted) aliphatic hydrocarbon radical, are suitable as selective herbicides. They are prepared by analogous processes via sulfonamides, some of which are new, of the formula (II) (see claim 4).