Distributed space time coding can achieve full spatial diversity in wireless relay networks. However, it requires accurate symbol-level synchronization and priori coordination between cooperative relay terminals, which is difficult to implement in distributed networks. In this paper, we propose a novel scheme based on interleaving to achieve cooperative diversity in both synchronous and asynchronous networks with little protocol overhead. A low complexity iterative detection algorithm is also proposed to combine signals from different relays at the receiver. The simulation results demonstrate the comparable performance to space-time codes based cooperative schemes which require perfect synchronization and coordination.