Curt Casali homered and had four RBIs, and Preston Tucker added a pinch-hit homer for Cincinnati, which has dropped four straight.
Jose Quintana (11-9) allowed two runs on six hits in five-plus innings — walking three and striking out two — to get his first win since Aug. 3.
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Reds starter Luis Castillo (7-11) allowed five runs on five hits in 3 1/3 innings.
Ian Happ drove in the Cubs’ first run with a two-out single in the second, and Murphy followed with a two-run shot for a 3-0 lead.
After Cincinnati got a pair of runs in the top of the fourth, Schwarber’s two-run shot in the bottom of the fourth restored the three-run advantage. Baez hit a solo blast in the fifth, and Anthony Rizzo’s run-scoring single in the sixth made it 7-2.
Chicago added three unearned runs in the seventh. The Reds scored four runs in the eighth against reliever Brandon Kintzler, who like Murphy was acquired in a midseason trade with the Washington Nationals. Casali hit a three-run homer and Tucker followed with a solo blast.
The Reds activated RF Scott Schebler (sprained right shoulder) before the game and optioned OF Aristides Aquino to Triple-A Pensacola. Schebler batted leadoff and went 1 for 5.
Reds: 1B Joey Votto (lower right leg) ran sprints on the field before the game. Manager Jim Riggleman said a decision on whether Votto will be activated for the finale of the series won’t be made until Sunday morning.
Reds RHP Homer Bailey (1-11, 6.21 ERA) faces RHP Kyle Hendricks (9-10, 4.04) in the finale of the four-game series on Sunday. Bailey is 0-4 with a 5.22 ERA in five starts since coming off the DL in late July, and Cincinnati is 1-16 in his 17 starts this season. Hendricks is 3-0 with a 1.83 ERA in six career starts against the Reds at Wrigley Field.