The invention relates to a process for the preparation of a compound of formula (I), which process comprises a) reacting a compound of formula (II), wherein X is chloro or bromo, with an organometallic species to (III) reacting the halobenzyne of formula (III) so formed with (IV) wherein R1 and R2 are hydrogen or C1-C6alkyl; to (V), b) hydrogenating V in the presence of a metal catalyst to (VI), c) ozonising (VI) to (VII) d) converting (VII) in the presence of a phosphane and CCI4 or CHCI3 to (VIII) (VIII), and either e1) reacting VIII with NH3 in the presence of a catalyst to (IX) and f) reacting IX in the presence of a base with the compound of formula (X), to the compound of formula (I); or e2) reacting the compound of formula (VIII), in the presence of a solvent, a base, a copper catalyst and at least one ligand with (Xa), to the compound of formula (I).