Borussia Dortmund cut the gap to Bundesliga leaders Bayern Munich with a 3-0 win at Union Berlin on Sunday. Dortmund are now six points behind Bayern, who were thrashed 4-2 by Bochum on Saturday. Captain Marco Reus scored a brace in the first half to give Dortmund the advantage, and Raphaël Guerreiro sealed the away win after the break. Kevin Möhwald seemed to have pulled one back for Union with some 15 minutes left but the potential lifeline was disallowed due to a foul on Dortmund defender Manuel Akanji. This was Dortmund’s first triumph at the An der Alten Försterei stadium since Union were…