Preheat the oven to 325 degrees F (165 degrees C).

Melt butter in a saucepan over medium heat. Add ketchup and brown sugar and stir until sugar dissolves. Whisk cornstarch into vinegar in a small bowl until smooth, then pour into the pan. Whisk in salt, soy sauce, and Worcestershire sauce and bring to a simmer while continuing to whisk constantly. Cook until thickened, about 2 minutes. Stir in pineapple and remove from the heat.

Arrange chicken pieces in a 9x13-inch baking dish; pour pineapple sauce over top.

Bake in the preheated oven until the sauce is bubbling and the chicken is browned and the juices run clear, about 45 minutes. An instant-read meat thermometer inserted into the thickest part of a thigh should read at least 165 degrees F (74 degrees C).