R1 to R3 are defined as mentioned at the outset and Z1 is a leaving group such as a halogen atom, a substituted hydroxyl, mercapto, sulphinyl, sulphonyl or sulphonyloxy group such as a chlorine or bromine atom, a methanesulfonyl or methanesulfonyloxy group, with piperazine or [1,4]diazepane or their salts.