β-Amino-α-Cyanoacrylates of formula I where the variables have the following meanings: R1 is n-alkyl, n-alkenyl or alkoxyalkyl; R2,R3 are alkyl, which may be partially or fully halogenated and/or may carry a substituent from the group consisting of cyano, alkoxy, haloalkoxy, alkylthio, haloalkylthio, C1-C6-alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl and haloalkylsulfonyl, are alkenyl or alkynyl; or R2 and R3 together with the carbon atom to which they are attached form a cycloalkyl ring in which one or two nonadjacent CH2 groups may be replaced by oxygen or sulfur, and where the cycloalkyl ring may be substituted by halogen or alkyl; R4 is hydrogen, halogen, cyano or alkyl, where the substituents R2, R3 and R4 or two of the radicals R2, R3 and R4 are not simultaneously methyl, and their agriculturally useful salts, processes and intermediates for their preparation; and the use of these compounds or of compositions comprising these compounds for controlling undesirable plants are described.