A process of preparing chiral N -acyl-(3-substituted)-(8-substituted)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine of general Formula I: or solvates thereof, wherein R 1 is alkyl, haloalkyl, hydroxyalkyl or alkoxyalkyl; R 2 is alkyl, alkoxyalkyl or haloalkyl; Ar is a phenyl group, optionally substituted by one or more substituent(s) selected from H, halo, alkyl, alkoxy, haloalkyl, nitrile and thiophen-2-yl; X 1 is N and X 2 is S or O; or X 1 is S and X 2 is N; --- represents a single or a double bond depending on X 1 and X 2; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; said process comprising the following steps: a) reacting a compound of Formula A: wherein R 1 is as defined above; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; with a compound of Formula B: wherein Ar is as defined above; and Y is hydroxyl or halo; so as to obtain a compound of Formula C: wherein the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; b) converting the compound of Formula C with a tri(C1-C2 alkyl)oxonium salt, a (C1-C2)alkylsulfate, a (C1-C2)chloroformate or PCl 5 /POCl 3 /(C1-C2)hydroxyalkyl, so as to obtain a compound of Formula D: wherein Ar and R 1 are as defined above; R 3 is C1-C2 alkyl; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; in the presence of a base; c) reacting the compound of Formula D with a compound of Formula E or a salt or solvate thereof, wherein X 1, X 2 and R 2 are as defined above; so as to obtain a compound of Formula I or solvate thereof. R 1 is alkyl, haloalkyl, hydroxyalkyl or alkoxyalkyl; R 2 is alkyl, alkoxyalkyl or haloalkyl; Ar is a phenyl group, optionally substituted by one or more substituent(s) selected from H, halo, alkyl, alkoxy, haloalkyl, nitrile and thiophen-2-yl; X 1 is N and X 2 is S or O; or X 1 is S and X 2 is N; --- represents a single or a double bond depending on X 1 and X 2; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; a) reacting a compound of Formula A: wherein R 1 is as defined above; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; with a compound of Formula B: wherein Ar is as defined above; and Y is hydroxyl or halo; so as to obtain a compound of Formula C: wherein the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; b) converting the compound of Formula C with a tri(C1-C2 alkyl)oxonium salt, a (C1-C2)alkylsulfate, a (C1-C2)chloroformate or PCl 5 /POCl 3 /(C1-C2)hydroxyalkyl, so as to obtain a compound of Formula D: wherein Ar and R 1 are as defined above; R 3 is C1-C2 alkyl; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; in the presence of a base; Ar and R 1 are as defined above; R 3 is C1-C2 alkyl; and the solid line with a star indicates that the individual enantiomers are meant, excluding racemic mixtures thereof; c) reacting the compound of Formula D with a compound of Formula E or a salt or solvate thereof, wherein X 1, X 2 and R 2 are as defined above; so as to obtain a compound of Formula I or solvate thereof.