Abstract: An improved condensation process for preparing N-[4-(3,4-dichlorophenyl)-3,4-dihydro-1(2H)-naphthalenylidene]methanamine from 4-(3,4-dichlorophenyl)-3,4-dihydro-1(2H)-naphthalenone and methylamine is disclosed. The process involves the use of a hydratable molecular sieve having a pore size that is at least about three Angstrom units in diameter as the dehydrating agent (catalyst) in a reaction-inert aprotic organic solvent. The ketimine final product so produced is known to be useful as an intermediate leading to cis-(1S)(4S)-N-methyl-4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-1-naphthal enamine (sertraline), which is an anti-depressant agent.