Compounds for treating spinal muscular atrophy

A process for the preparation of a compound of formula (I):

• or a pharmaceutically acceptable salt thereof, wherein
• R1 is hydrogen or C1-7-alkyl;
• R2 is hydrogen, cyano, C1-7-alkyl, C1-7-haloalkyl or C3-8-cycloalkyl;
• R3 is hydrogen, C1-7-alkyl, or C3-8-cycloalkyl;
• A is N-heterocycloalkyl or NR12R13, wherein N-heterocycloalkyl comprises 1 or 2 nitrogen ring atoms and is optionally substituted with 1, 2, 3 or 4 substituents selected from R14;
• R12 is piperidinyl optionally substituted with 1, 2, 3 or 4 substituents selected from R14;
• R13 is hydrogen, C1-7-alkyl or C3-8-cycloalkyl;
• R14 is independently selected from hydrogen, C1-7-alkyl, amino, amino-C1-7-alkyl, C3-8-cycloalkyl and heterocycloalkyl or two R14 together form C1-7-alkylene;
• with the proviso that if A is N-heterocycloalkyl comprising only 1 nitrogen ring atom, then at least one R14 substituent is amino or amino-C1-7-alkyl;
• wherein the process comprises an aromatic nucleophilic substitution reaction between a compound of formula (VI):
• wherein
• R1 is hydrogen or C1-7-alkyl;
• R2 is hydrogen, cyano, C1-7-alkyl, C1-7-haloalkyl or C3-8-cycloalkyl;
• R3 is hydrogen, C1-7-alkyl, or C3-8-cycloalkyl;
• Y is halogen or trifluoromethanesulfonate;
• or a salt thereof;
• with a compound of formula M-A by heating in a solvent, wherein
• M is hydrogen, sodium or potassium, and wherein M is linked to A via a nitrogen atom of A.