Aminoaryl sulphonamide derivatives as functional 5-HT6 ligands

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

• or a pharmaceutically acceptable salt thereof wherein:
• —Ar represents any one group selected from phenyl, naphthyl, a monocyclic or bicyclic heteroaryl, each of which may be further substituted by one or more independent substituents and those substituents are defined as R1;
• R represents either a hydrogen atom, (C1-C3)alkyl or halo(C1-C3)alkyl group;
• R1 and R4 independently represents one or multiple substitutions on the benzene ring, and includes a hydrogen, halogen, cyano, (C1-C3)alkyl, halo(C1-C3)alkyl, (C1-C3)alkoxy, halo(C1-C3)alkoxy, cyclo(C3-C6)alkyl or cyclo(C3-C6)alkoxy;
• R2 whenever present, represents hydrogen, halogen, (C1-C3)alkyl, halo(C1-C3)alkyl, (C1-C3)alkoxy or halo(C1-C3)alkoxy;
• R3 whenever present, represents hydrogen, (C1-C3)alkyl or halo(C1-C3)alkyl;
• R5 and R6 represents either hydrogen or methyl
• which comprises of contacting a compound of formula (a) wherein R1, R4 and Ar are as defined in claim-1 earlier, with a piperidone derivative of formula (b):
• wherein, R5, R6 and R are as defined above by reductive amination using a suitable reducing agent/catalyst in presence of inert solvent at ambient temperature to obtain a compound of formula (I).

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

• or a pharmaceutically acceptable salt thereof wherein:
• —Ar represents any one group selected from phenyl, naphthyl, a monocyclic or bicyclic heteroaryl, each of which may be further substituted by one or more independent substituents and those substituents are defined as R1;
• R represents either a hydrogen atom, (C1-C3)alkyl or halo(C1-C3)alkyl group;
• R1 and R4 independently represents one or multiple substitutions on the benzene ring, and includes a hydrogen, halogen, cyano, (C1-C3)alkyl, halo(C1-C3)alkyl, (C1-C3)alkoxy;
• halo(C1-C3)alkoxy, cyclo(C3-C6)alkyl or cyclo(C3-C6)alkoxy;
• R2 whenever present, represents hydrogen, halogen, (C1-C3)alkyl, halo(C1-C3)alkyl, (C1-C3)alkoxy or halo(C1-C3)alkoxy;
• R3 whenever present, represents hydrogen, (C1-C3)alkyl or halo(C1-C3)alkyl;
• R5 and R6 represents either hydrogen or methyl
• which comprises of carrying out nucleophilic substitution in a compound of formula (a) herein, R1, R4 and Ar are as defined in claim-1 earlier, with a piperidinyl halide of formula (c):
• wherein R5, R6 and R are as defined above;
• X represents as a halogen atom such as fluoro, chloro or iodo, using a suitable base and inert solvent at a suitable temperature.