A compound of formula: wherein: A is a phenyl, pyridyl, pyridazinyl, pyrimidinyl or pyrazinyl ring which is substituted or unsubstituted, and when substituted A contains 1 to 3 substituents independently selected from: halo, =O, -CN, C 1-4 alkyl, C 1-4 haloalkyl, C 3-6 cycloalkyl, -OR A, -NR A R B, SO 2 R A and SOR A; R 1 is a substituted or unsubstituted heterocyclic moiety which either contains 5 or 6 atoms in a single ring or 8, 9, 10 or 11 atoms in a fused bicyclic ring system, when substituted R 1 contains 1 to 4 substituents independently selected from: halo, -OR A, -NR A R B, =O, -OC R C, -C R C, -C OR A,-NR A C R C, -C NR A R B, -SO 2 R C, -SOR C, -NR A SO 2 R C, -SO 2 NR A R B, -CN, C 1-4 alkyl, C 1-4 haloalkyl and C 3-6 cycloalkyl; X is N, O or S; Y is -CR 2B W or -CW; W represents: -het 1 -R 3 or -het 2, in which het 1 is a five or six membered heterocyclic ring, and het 2 is a heterocyclic ring system containing 8, 9 or 10 atoms in a fused bicyclic ring system; and in which each of het 1 and het 2 may be independently unsubstituted or substituted and contain 1 or 2 substituents independently selected at each occurrence from: halo, -OR A, -CN, C 1-4 alkyl, C 1-4 haloalkyl, C 3-6 cycloalkyl, in which the aforementioned alkyl, haloalkyl and cycloalkyl groups may themselves also be unsubstituted or substituted with 1 to 3 groups independently selected from: -OR A, -CN, -NR A R B; Z is N, O, S, -CR 2C, -CR 2C R 2D; R 2A, R 2B, R 2C and R 2D are each independently selected at each occurrence from: H, halo, -OR A, -CN, C 1-4 alkyl, C 1-4 haloalkyl and C 3-6 cycloalkyl; R 3 is selected from substituted or unsubstituted: C 1-6 alkyl, C 1-6 haloalkyl, a carbocyclic moiety or a heterocyclic moiety, wherein the carbocyclic moiety and heterocyclic moiety either contain 5 or 6 atoms in a single ring or 8, 9 or 10 atoms in a fused bicyclic ring system, and when substituted R 3 contains 1 to 4 substituents independently selected from: halo, -OR A, -NR A R B, -SO 2 R C, -SOR C, -CN, C 1-4 alkyl, C 1-4 haloalkyl, C 3-6 cycloalkyl in which the aforementioned alkyl, haloalkyl and cycloalkyl groups may themselves also be unsubstituted or substituted with 1 to 3 groups independently selected from: -OR A, -CN, -SOR C and -NR A R B; R A and R B are each independently selected from H, C 1-4 alkyl and C 1-4 haloalkyl; and R C is selected from C 1-4 alkyl and C 1-4 haloalkyl. A is a phenyl, pyridyl, pyridazinyl, pyrimidinyl or pyrazinyl ring which is substituted or unsubstituted, and when substituted A contains 1 to 3 substituents independently selected from: halo, =O, -CN, C 1-4 alkyl, C 1-4 haloalkyl, C 3-6 cycloalkyl, -OR A, -NR A R B, SO 2 R A and SOR A; R 1 is a substituted or unsubstituted heterocyclic moiety which either contains 5 or 6 atoms in a single ring or 8, 9, 10 or 11 atoms in a fused bicyclic ring system, when substituted R 1 contains 1 to 4 substituents independently selected from: halo, -OR A, -NR A R B, =O, -OC R C, -C R C, -C OR A,-NR A C R C, -C NR A R B, -SO 2 R C, -SOR C, -NR A SO 2 R C, -SO 2 NR A R B, -CN, C 1-4 alkyl, C 1-4 haloalkyl and C 3-6 cycloalkyl; X is N, O or S; Y is -CR 2B W or -CW; W represents: -het 1 -R 3 or -het 2, in which het 1 is a five or six membered heterocyclic ring, and het 2 is a heterocyclic ring system containing 8, 9 or 10 atoms in a fused bicyclic ring system; and in which each of het 1 and het 2 may be independently unsubstituted or substituted and contain 1 or 2 substituents independently selected at each occurrence from: halo, -OR A, -CN, C 1-4 alkyl, C 1-4 haloalkyl, C 3-6 cycloalkyl, in which the aforementioned alkyl, haloalkyl and cycloalkyl groups may themselves also be unsubstituted or substituted with 1 to 3 groups independently selected from: -OR A, -CN, -NR A R B; Z is N, O, S, -CR 2C, -CR 2C R 2D; R 2A, R 2B, R 2C and R 2D are each independently selected at each occurrence from: H, halo, -OR A, -CN, C 1-4 alkyl, C 1-4 haloalkyl and C 3-6 cycloalkyl; R 3 is selected from substituted or unsubstituted: C 1-6 alkyl, C 1-6 haloalkyl, a carbocyclic moiety or a heterocyclic moiety, wherein the carbocyclic moiety and heterocyclic moiety either contain 5 or 6 atoms in a single ring or 8, 9 or 10 atoms in a fused bicyclic ring system, and when substituted R 3 contains 1 to 4 substituents independently selected from: halo, -OR A, -NR A R B, -SO 2 R C, -SOR C, -CN, C 1-4 alkyl, C 1-4 haloalkyl, C 3-6 cycloalkyl in which the aforementioned alkyl, haloalkyl and cycloalkyl groups may themselves also be unsubstituted or substituted with 1 to 3 groups independently selected from: -OR A, -CN, -SOR C and -NR A R B; R A and R B are each independently selected from H, C 1-4 alkyl and C 1-4 haloalkyl; and R C is selected from C 1-4 alkyl and C 1-4 haloalkyl.