A new and simplified process for preparing N-[4-(3,4-dichlorophenyl)-3,4-dihydro-1(2H)-naphthalenylidene]methanamine and a telescoped process for the synthesis of (1S-cis)-4-(3,4-dichlorophenoI)-1 2,3,4-tetrahydro-N-methyl-1-naphthalenamine mandelate:: Key intermediates in the synthesis of sertraline hydrochloride

N-[4-(3,4-Dichlorophenyl)-3,4-dihydro-1(2H)-naphthalenylidene]-methanamine, sertraline imine (3), is an intermediate for the synthesis of Zoloft, sertraline hydrochloride (1). A cleaner, simpler, and more efficient alternative to the Schiff base-mediated formation of sertraline imine has been developed and is presented in this paper. The condensation reaction between 4-(3,4-dichlorophenyl)-3,4-dihydro-1(2H)-naphthalone, sertraline tetralone (2), and monomethylamine was carried out in ethanol, without the need for classical dehydrating agent, such as TiCl4, or more novel approaches, such as molecular sieves, both of which produce hazardous byproducts and solid wastes. The low solubility of the imine 3 in this type of solvent is exploited, such that the reaction equilibrium favorably enhances the imine formation. Furthermore, an improved and highly selective catalytic reduction of 3 with Pd/CaCO3 catalyst in ethanol as the reaction solvent, followed by the resolution of the racemic cis isomer (6) with D-(-)-mandelic acid results in a more efficient telescoped commercial process to (1S-cis)-4(3,4-dichlorophenol)-1,2,3,4-tetrahydro-N-methyl-1-naphthalen- amine mandelate, sertraline mandelate (4). This new process has been implemented commercially and eliminates the use of hazardous material such as TiCl4, significantly reduces undesirable byproducts, reduces the number of intermediate isolations, and improves the overall process yield and productivity on industrial scale.