An efficient synthetic method of functionalized naphthalenes having hydrogen, alkyl, alkenyl, aryl, or heteroaryl groups on the 4-position and ethoxycarbonyl group on the 2-position was developed through selective Pt-catalyzed 6-<i>endo</i> intramolecular hydroarylation of ethyl (<i>E</i>)-2-ethynyl/alkynyl cinnamates