In a nonstick wok or large frypan over high heat, warm oil. Add chicken and saute until firm and well-browned, about 6 minutes. Remove chicken and set aside. Add pineapple and molasses to wok and stir-fry until the pineapple is brown and tender. Stir in the lime juice, red pepper flakes, scallions and chicken. Saute until scallions are bright green and the chicken is fully cooked, about 5 minutes. Toss in ginger and serve over rice.