A compound of formula: wherein, R 1 is C 1 -C 12 alkyl or C 1 -C 6 haloalkyl; R 2 is hydroxy, C 2 -C 6 acyloxy, C 2 -C 6 haloacyloxy, C 1 -C 6 alkoxyC 1 -C 6 alkoxy, C 1 -C 6 haloalkoxyC 1 -C 6 alkoxy, C 1 -C 6 alkoxyC 1 -C 6 haloalkoxy, C 2 -C 6 acyloxyC 1 -C 6 alkoxy, C 2 -C 6 haloacyloxyC 1 -C 6 alkoxy, or C 2 -C 6 acyloxyC 1 -C 6 haloalkoxy; R 3 is hydrogen, C 1 -C 6 alkyl, C 1 -C 6 alkoxy or C 3 -C 8 cycloalkyl; R 4 and R 5 are each independently C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, C 1 -C 6 haloalkyl or C 1 -C 6 alkoxyC 1 -C 6 alkyl; R 6 is hydrogen, C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, aryl or heteroaryl, wherein the heteroaryl moiety is a 5- or 6-membered aromatic ring which comprises 1, 2, 3 or 4 heteroatoms individually selected from N, O and S, and wherein the aryl and heteroaryl moieties are each optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; R 7 is hydrogen, C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, aryl or heteroaryl, wherein the heteroaryl moiety is a 5- or 6-membered aromatic ring which comprises 1, 2, 3 or 4 heteroatoms individually selected from N, O and S, and wherein the aryl and heteroaryl moieties are each optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; or R 6 and R 7 together with the carbon atom to which they are attached form a C 3 -C 8 cycloalkyl ring which is optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; R 8 is C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, aryl, aryloxy, heteroaryl, or heteroaryloxy, wherein the heteroaryl moiety is a 5- or 6-membered aromatic ring which comprises 1, 2, 3 or 4 heteroatoms individually selected from N, O and S, and wherein the aryl and heteroaryl moieties are each optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; R 9 is halogen, cyano, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, or C 1 -C 4 haloalkoxy; or a salt or an N-oxide thereof. R 1 is C 1 -C 12 alkyl or C 1 -C 6 haloalkyl; R 2 is hydroxy, C 2 -C 6 acyloxy, C 2 -C 6 haloacyloxy, C 1 -C 6 alkoxyC 1 -C 6 alkoxy, C 1 -C 6 haloalkoxyC 1 -C 6 alkoxy, C 1 -C 6 alkoxyC 1 -C 6 haloalkoxy, C 2 -C 6 acyloxyC 1 -C 6 alkoxy, C 2 -C 6 haloacyloxyC 1 -C 6 alkoxy, or C 2 -C 6 acyloxyC 1 -C 6 haloalkoxy; R 3 is hydrogen, C 1 -C 6 alkyl, C 1 -C 6 alkoxy or C 3 -C 8 cycloalkyl; R 4 and R 5 are each independently C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, C 1 -C 6 haloalkyl or C 1 -C 6 alkoxyC 1 -C 6 alkyl; R 6 is hydrogen, C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, aryl or heteroaryl, wherein the heteroaryl moiety is a 5- or 6-membered aromatic ring which comprises 1, 2, 3 or 4 heteroatoms individually selected from N, O and S, and wherein the aryl and heteroaryl moieties are each optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; R 7 is hydrogen, C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, aryl or heteroaryl, wherein the heteroaryl moiety is a 5- or 6-membered aromatic ring which comprises 1, 2, 3 or 4 heteroatoms individually selected from N, O and S, and wherein the aryl and heteroaryl moieties are each optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; or R 6 and R 7 together with the carbon atom to which they are attached form a C 3 -C 8 cycloalkyl ring which is optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; R 8 is C 1 -C 12 alkyl, C 3 -C 8 cycloalkyl, aryl, aryloxy, heteroaryl, or heteroaryloxy, wherein the heteroaryl moiety is a 5- or 6-membered aromatic ring which comprises 1, 2, 3 or 4 heteroatoms individually selected from N, O and S, and wherein the aryl and heteroaryl moieties are each optionally substituted by 1, 2 or 3 substituents, which may be the same or different, selected from R 9; R 9 is halogen, cyano, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, or C 1 -C 4 haloalkoxy; or a salt or an N-oxide thereof.