The Catalan giants were ready to pay Seri's €40m release clause and had agreed a contract.
Dembele moved to Barcelona from Dortmund for a club-record fee of €105m.
Pereira will spend the 2017/18 campaign with La Liga outfit Valencia.
Director Albert Soler claims Argentine will formally sign new deal agreement soon.
Director Albert Soler says Catalan giants were not prepared to engage in such an inflated market.
Munir spent the last season on loan at Valencia and scored six goals in the process.
Divisive striker was substituted after 83 minutes of forgettable 2018 World Cup qualifier in Montevideo.
The Premier League side rejected three bids for the playmaker this summer.
Lemar turned down a chance to join Arsenal on transfer deadline day.
The 21-year-old became Tottenham's record signing after his £42m arrival from Ajax.
Three clubs seemingly in the running for Portuguese midfielder as transfer deadline approaches.
Antoine Grizmann and Paulo Dybala are also on a three-man shortlist for Barcelona's 'Plan B'.
Brazilian's departure could give Thomas Vermalen a chance to serve as fourth choice centre-back this season.
Los Colchoneros midfielder claims transfer, while complicated, would be "very exciting" for the club.
Costa is determined to return to Atletico Madrid but Ronald Koeman would welcome him at Goodison Park.
Recent reports claim that the Catalans could offer €140m plus add-ons to sign the Liverpool star.
Midfielder says that Liverpool, Arsenal, PSG, Juventus and Roma are also interested in his signature.
Brazilian playmaker looks very unlikely to leave Anfield at this stage of the summer.
Turan, 30, is not in Barcelona coach Ernesto Valverde's plans for the season.
Reports in Germany claim an official announcement will be made on Friday afternoon.
Bundesliga outfit are reportedly eager to avoid seeing German international join Bayern Munich for free next summer.
The new signing missed the weekend's 2-0 victory over Real Betis due to bureaucratic issues.