Disclosed are compounds of Formulae 1, 1a, 1b and 2, wherein R1, R1a, R1b, R2, R3 and R4 are as defined in the disclosure. Also disclosed are compositions containing the compounds of Formulae 1, 1a and 1b, and methods for controlling a parasitic nematode comprising contacting the parasitic nematode or its environment with a biologically effective amount of a compound or composition of Formulae 1, 1a, 1b and 2.