In a small bowl, combine reserved pineapple juice, soy sauce, oil, onion, garlic and brown sugar, mixing well.
Pour mixture over pork chops, cover and marinate in refrigerator at least 2 hours.
Remove chops from marinade. Grill over medium heat 30-35 minutes, turning frequently.
Place a pineapple ring on each chop during the last few minutes of cooking time.