Brouwer's tally with Benoit Pouliot off for slashing handed the Capitals a 3-games-to-2 advantage over the Bruins in their best-of-seven Eastern Conference quarterfinal series.
Jay Beagle, Mike Knuble and Alexander Semin also had goals for the Capitals while Braden Holtby turned aside 34-of-37 shots for Washington, which will try to close out the defending NHL champions Sunday in Boston.
The Bruins got goals from Johnny Boychuk, Brad Marchand and Dennis Seidenberg but still fell, placing them in danger of being eliminated in the first round for the first time in four years.
Tim Thomas made 28 saves in the loss.
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