On the opening lap of the race, polesitter Razgatlioglu, Rea and Michael Ruben Rinaldi went three-wide into Turn 6, with the championship leader holding onto the lead as Rea slipped behind Rinaldi.
Rea would run wide at the same corner three laps later, allowing Redding to breeze past him and begin an intra-Ducati battle for second.
An opportunity opened up for Redding when Rinaldi ran wide into Turn 6 on lap 7 and the British rider duly took advantage of the situation to pass his teammate into the final corner.
Once clear of Rinaldi, Redding set about chasing the Yamaha of Razgatlioglu, who had won the opening race this morning to extend his lead over Rea in the standings.
After spending the middle stages of the race in his shadows, Redding made a bold move over Razgatlioglu under braking for the Turn 10 right-hander on lap 17, taking the lead for the first time in the race.
However, Razgatlioglu didn’t allow Redding to run away at the front and, after an unsuccessful attempt at Turn 6, he came from a long way back to repass the Ducati into the final corner.
Razgatlioglu covered the inside line into the same corner on the penultimate lap and then did enough to hold on to the lead on the final lap, scoring his 10th victory of the season and 14th of his career.
With Rea finishing down in fifth in a race to forget for the Kawasaki star, Razgatlioglu takes a 20-point advantage into the final three rounds of the season.
Behind race winner Razgatlioglu and Redding, Alvaro Bautista finished third to bag a second podium for Honda in as many rounds.
The Spanish rider, who will join Ducati next year, demoted the second Yamaha of Andrea Locatelli to fourth after passing the Italian at the final turn just two laps from the finish.
Rinaldi was unable to keep up with the frontrunners following his early battle with Redding for second, slipping to seventh at the finish behind Rea and Axel Bassani on the Motocorsa Ducati.
Michael van der Mark climbed from 12th on the grid to finish eighth on the BMW, while the top 10 was rounded out by ex-MotoGP rider Loris Baz – replacing the injured Chaz Davies at Go Eleven Ducati – and GRT Yamaha’s Garrett Gerloff.
Eugene Laverty – substituting for Tom Sykes – was classified 11th ahead of Leon Haslam, who endured another difficult race on the factory Honda.
Kawasaki rider Alex Lowes didn’t take part in the second race to allow his hand to recover fully, having suffered a fracture in his hand last weekend in Barcelona.