Son puts himself in timeout! Help!

mj

My 2.5 year old son is the most stubborn, strong willed child I've ever met. He doesn't care about the consequences. I don't believe in spanking so his consequences are "crime related" or classic timeout with righting his wrongs when he gets out. For example, if he threw something at someone, he needs to pick it up and put it back, then apologize. But over the last few weeks, he doesn't care. His main issues are throwing items, hitting, and not listening to directions. Now, if I say "Dont throw that. Set it down nicely." He throws it, tosses his paci over his shoulder (he can't have it in timeout), and sits himself in timeout. While he is in there he hums and smiles. Then when he decides he is done with timeout before his time is up, he just gets out. If I set him back in timeout, he gets up again. And we continue back and forth forever. There's no end. Unless I sit with him and physically hold him in timeout. And even then I'm like...is this even productive? Especially because having me right there, he uses the opportunity to be physical for attention. Guys please help! Any suggestions are welcome!