c) converted by a reductive reaction followed by a deoxohalogenation reaction, optionally an N-alkylation reaction in order to introduce R4 if R4 is desired to be not equal to hydrogen, and finally a hydrolytic reaction to obtain a compound of formula V wherein R1, R3 and R4 are as defined above in formula I and Halo is a halogen atom, and optionally convert the above resulting compound V into ano