1. In a medium saucepan, bring the mandarin oranges with their syrup and the cinnamon to a boil. Continue boiling until reduced to 3/4 cup, about 10 minutes.
2. Divide half of the pound cake cubes among 8 trifle glasses and spoon half of the orange sauce on top. Divide the pineapple chunks among the glasses, then top with the remaining cake and sauce.
3. Whisk the cream until soft peaks form. Divide among the glasses and top with the coconut.
Tip: The orange sauce can be refrigerated in an airtight container for up to 1 week.