A compound of formula: wherein R 1 is hydrogen, cyano, formyl, C 1 -C 6 alkylcarbonyl, C 1 -C 6 alkoxyC 1 -C 6 alkylcarbonyl, C 1 -C 6 haloalkylcarbonyl, C 1 -C 6 alkoxycarbonylC 1 -C 4 alkylcarbonyl, C 3 -C 6 cycloalkylcarbonyl, C 1 -C 6 alkoxycarbonyl, C 1 -C 6 alkoxycarbonylcarbonyl, C 1 -C 6 alkoxyC 1 -C 4 alkoxycarbonyl, C 2 -C 6 alkenyloxycarbonyl, C 2 -C 6 alkynyloxycarbonyl, C 1 -C 6 alkylsulfanylcarbonyl, phenylcarbonyl, phenoxycarbonyl, or heteroarylcarbonyl, wherein the heteroaryl is a 5- or 6-membered aromatic monocyclic ring comprising 1 or 2 heteroatoms individually selected from nitrogen, oxygen and sulfur; R 2 is hydrogen, halogen, cyano, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkyl, or HC NH-; R 3 is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkyl, or C 3 -C 4 cycloalkyl; R 4 is C 1 -C 8 alkyl, C 1 -C 8 haloalkyl, C 1 -C 8 alkoxy, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkylC 1 -C 2 alkyl, phenyl, phenylC 1 -C 2 alkyl, heteroaryl or heteroarylC 1 -C 2 alkyl wherein the heteroaryl is a 5- or 6-membered aromatic monocyclic ring comprising 1, 2, 3 or 4 heteroatoms individually selected from nitrogen, oxygen and sulfur, heterocyclyl or heterocyclylC 1 -C 2 alkyl wherein the heterocyclyl is a 4-, 5- or 6-membered non-aromatic monocyclic ring comprising 1, 2 or 3 heteroatoms individually selected from nitrogen, oxygen and sulfur, or a 5- to 10-membered non-aromatic spirocyclic carbobi- or carbotri-cyclyl ring system optionally comprising 1, 2, 3, 4 or 5 heteroatoms individually selected from nitrogen, oxygen and sulfur, optionally bonded to the rest of the molecule through a C 1 -C 2 alkylene linker, and wherein each cycloalkyl, phenyl, heteroaryl or heterocyclyl group is optionally substituted with 1 to 3 groups represented by R 5; and R 5 is halogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, or C 1 -C 4 haloalkyl; or a salt or an N-oxide thereof. R 1 is hydrogen, cyano, formyl, C 1 -C 6 alkylcarbonyl, C 1 -C 6 alkoxyC 1 -C 6 alkylcarbonyl, C 1 -C 6 haloalkylcarbonyl, C 1 -C 6 alkoxycarbonylC 1 -C 4 alkylcarbonyl, C 3 -C 6 cycloalkylcarbonyl, C 1 -C 6 alkoxycarbonyl, C 1 -C 6 alkoxycarbonylcarbonyl, C 1 -C 6 alkoxyC 1 -C 4 alkoxycarbonyl, C 2 -C 6 alkenyloxycarbonyl, C 2 -C 6 alkynyloxycarbonyl, C 1 -C 6 alkylsulfanylcarbonyl, phenylcarbonyl, phenoxycarbonyl, or heteroarylcarbonyl, wherein the heteroaryl is a 5- or 6-membered aromatic monocyclic ring comprising 1 or 2 heteroatoms individually selected from nitrogen, oxygen and sulfur; R 2 is hydrogen, halogen, cyano, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkyl, or HC NH-; R 3 is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkyl, or C 3 -C 4 cycloalkyl; R 4 is C 1 -C 8 alkyl, C 1 -C 8 haloalkyl, C 1 -C 8 alkoxy, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkylC 1 -C 2 alkyl, phenyl, phenylC 1 -C 2 alkyl, heteroaryl or heteroarylC 1 -C 2 alkyl wherein the heteroaryl is a 5- or 6-membered aromatic monocyclic ring comprising 1, 2, 3 or 4 heteroatoms individually selected from nitrogen, oxygen and sulfur, heterocyclyl or heterocyclylC 1 -C 2 alkyl wherein the heterocyclyl is a 4-, 5- or 6-membered non-aromatic monocyclic ring comprising 1, 2 or 3 heteroatoms individually selected from nitrogen, oxygen and sulfur, or a 5- to 10-membered non-aromatic spirocyclic carbobi- or carbotri-cyclyl ring system optionally comprising 1, 2, 3, 4 or 5 heteroatoms individually selected from nitrogen, oxygen and sulfur, optionally bonded to the rest of the molecule through a C 1 -C 2 alkylene linker, and wherein each cycloalkyl, phenyl, heteroaryl or heterocyclyl group is optionally substituted with 1 to 3 groups represented by R 5; and R 5 is halogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, or C 1 -C 4 haloalkyl; or a salt or an N-oxide thereof.