Boychuk's blast from the right point threaded through traffic and eluded Craig Anderson 6:41 into the final frame, handing Boston a 4-3 lead. Daniel Paille added an insurance tally 37 seconds later for the Bruins.
Tim Thomas stopped 23-of-26 shots, including 9-of-10 in the final period, to earn the win.
Nick Foligno notched a goal and two assists while Anderson finished with 36 saves for the Senators, whose six-game winning streak came to an end.
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