A Pd-catalyzed synthesis of 3,4,5-trisubstituted cyclopentenes from diazabicyclic olefins and o-iodobenzoates has been developed. The hitherto unknown cascade process involves three stages: carbopalladation, oxypalladation and a Tsuji–Trost reaction. We have also developed a facile route involving a novel benzylic C–H activation towards cyclopentenoindane moieties.