1-Methoxynaphthalene (I) was lithiated with n-butyllithium and subsequently treated with N-methylformanilide (II) to give the 2-naphthaldehyde (III). The Knoevenagel condensation of (III) with the rhodanineacetic acid (IV) in the presence of NaOAc in AcOH provided the target 5-(alkylidene)thiazolidine.