PROCESS FOR THE PREPARATION OF TETRAZINE DERIVATIVES

摘要

The present invention provides a process for the preparation of a tetrazine derivative of formula (I), or a pharmaceutically acceptable salt thereof wherein R1 represents a hydrogen atom, a straight or branched C1-C6 alkyl group, C2-C6 alkenyl group or C2-C6 alkynyl group, which C1-C6 alkyl group, C2-C6 alkenyl group and C2-C6 alkynyl group is unsubstituted or substituted with 1, 2 or 3 substituents selected from halogen atoms, straight or branched C1-C4 alkoxy groups, C1-C4 alkylthio groups, C1-C4 alkylsulphinyl groups, C1-C4 alkylsulphonyl groups and phenyl groups, which phenyl groups are unsubstituted or substituted with one or more substituents selected from C1-C4 alkyl groups, C1-C4 alkoxy groups and nitro groups; or R1 represents a C3-C8 cycloalkyl group; and R2 represents a group of formula—(C═O)NR3R4, wherein R3 and R4 are independently selected from hydrogen atoms, C1-C4 alkyl groups, C2-C4 alkenyl groups and C3-C8 cycloalkyl groups, which process comprises: i) providing a compound N of formula (III), wherein R1 is as defined; R1—N═C═O ii) absorbing the compound of formula (III) into a solvent to obtain a solution of the compound of formula (III); iii) adding to the thus obtained solution a compound of formula (II), to obtain a compound of formula (I), as defined above, wherein R2 is as defined above; iv) decomposing any excess compound of formula (III) remaining by addition of water; and v) optionally salifying the thus obtained compound with a pharmaceutically acceptable acid, or base.