Latos (1-0) retired the first batters and 10 and 15 of the first 16 he faced. He walked one and struck out four over seven-plus innings.
After he walked Dioner Navarro and Luis Valbuena singled to open the eighth, he was lifted for Jonathan Broxton, who got out of the jam. Aroldis Chapman pitched a one-hit ninth for his fourth save. That gave the Reds a combined five-hit shutout.
Chicago starter Jeff Samardzija (1-4) pitched nearly as well, going six innings and allowing seven hits while walking three and striking out eight. Three of the strikeouts came in the third after Cincinnati opened with two singles.
Samardzija got two outs in the sixth but Frazier crushed a 2-1 pitch well beyond the wall in straightaway center. It was his sixth home run of the season.
Samardzija lost his fourth consecutive decision but his earned run average dropped to 3.03.