Abstract: A process for the preparation of compounds of Formula I and their pharmaceutically acceptable acid addition salt wherein, R1 is phenyl or substituted phenyl R2 is selected from a group consisting of phenyl which is unsubstituted or substituted with 1 or 2 substituents, each independently selected from Cl, F, or pyridine, or naphthalene, or NHCOR4 wherein R4 is aryl, unsubstituted or substituted heteroaryl, unsubstituted or substituted heterocyclyl. R3 is selected from a group of formula wherein R5 is phenyl which is unsubstituted or substituted with 1 or 2 substituents each independently selected from the group consisting of halogen, C1-C4 alkyl, C1-C4 alkoxy, nitro, amino, haloalkyl, haloalkoxy etc.

Abstract: A novel method for preparing a compound of formula I which comprises of coupling the piperazine derivative of formula II with alkyl halide containing compound of the formula III by heating in solvent free conditions or, optionally, in a minimum quantity of non-aqueous suspending liquid, in presence of a catalyst and a neutralizing agent to neutralize the hydrohalic acid.