A compound of Formula (1) wherein R1 represents hydrogen, halo, a C1-C4 alkyl group, a C1-C4 alkylhalide group, a C1-C4 alkoxy-C2-C4 alkyl group, a C2-C4 alkenyl group, a C2-C4 alkynyl group or a C3- C7 cyclo alkyl group； R2 represents Formula (1)' or Formula (1)'' a tautomer thereof； and R3 represents hydrogen, a C1-C4 alkyl group, a C1-C4 alkoxy-C2-C4 alkyl group or a C7 cyclo alkyl group； or a pharmaceutically acceptable salt or solvate thereof. Processes to prepare said compounds and novel intermediates are also claimed. Such compound finds utility in treating neuropathic pain and disorders of the central nervous system.
