Corinthians beat Botafogo to extend lead
Striker Liedson opened the scoring for Corinthians a minute before half-time and midfielder Paulinho made the game safe in a counter-attack in the final minute.
Corinthians, who a day earlier pulled out of a bid to bring back Argentine Carlos Tevez from Manchester City, have 28 points from 10 matches after seven consecutive victories.
Sao Paulo are second on 21 points and Flamengo third a point further back after a 0-0 draw at fourth-placed Palmeiras.
Corinthians hope to give Adriano his debut in the coming weeks. The former Brazil and Inter Milan striker was signed earlier in the year but has yet to play for them after Achilles tendon surgery in April.
Struggling champions Fluminense announced they had signed three players before Wednesday night's closure of Brazil's transfer window for signings from abroad.
Fluminense signed Alejandro Martinuccio from South American champions Penarol, 18-year-old River Plate midfielder Manuel Lanzini and have taken former Brazil striker Rafael Sobis of UAE side Al Jazira on loan.