Heterocyclic compounds

A heterocyclic compound of the formula

• wherein
• R1 represents a hydrogen atom or a methyl group,
• A represents an ethylene group which may be substituted by methyl,
• X represents an oxygen or sulfur atom or the group
• in which R2 represents a hydrogen atom, a C1-C4 alkyl group which may be substituted by a substituent selected from halogens, C1-C4 alkoxy groups, C1-C4 alkylthio groups and cyano, a C2-C4 alkenyl group, a C2-C4 alkynyl group, a pyridylmethyl group which may be substituted by halogen and/or methyl, a benzyl group which may be substituted by halogen and/or methyl, a formyl group, an alkylcarbonyl group having 1 to 2 carbon atoms in the alkyl moiety which may be substituted by halogen, a phenylcarbonyl group which may be substituted by halogen and/or methyl, an alkoxy or alkylthiocarbonyl group having 1 to 4 carbon atoms in the alkyl moiety, a phenoxycarbonyl group, a C1-C4 alkylsulfonyl group which may be substituted by halogen or a phenylsulfonyl group which may be substituted by methyl,
• R3 represents a hydrogen atom or a C1-C7 alkyl group, and
• Z represents a 3-pyridyl group or a 4-pyridyl group optionally substituted by at least one substituent selected from halogen atoms, alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, alkylthio groups having 1 to 4 carbon atoms, alkylthio groups having 1 to 4 carbon atoms, haloalkyl groups having 1 to 4 carbon atoms, haloalkoxy groups having 1 to 4 carbon atoms, alkylsulfonyl groups having 1 to 4 carbon atoms, a cyano group and a nitro group.