Barcelona lead Real by three points with seven matches to play ahead of Wednesday's home clash with Deportivo La Coruna, while their title rivals travel to Almeria on Thursday.
After Donnelly's goal helped Tyrone leadbyseven, Daniel McLaughlin, Dermot Molloy and Karl Lacey all contributed two points as Donegal moved ahead by the interval.
Southerland hit a pair of 3s early in the second half to extend Syracuse's lead to 12, but Hopkins kept the Hoyas in it by scoring their first sevenpoints after halftime.