(S)-N,N-Dimethyl-3-(1-naphthalenyloxy)-3-(2-thienyl)propanamine maleate (DNT-maleate) and polymorphs of DNT-maleate, compositions of DNT-maleate and its polymorphs, processes for the preparation of DNT-maleate and its polymorphs, and processes for the preparation of duloxetine hydrochloride from DNT-maleate are provided.