The match was played in an empty ground in Montpellier after Ligue 2 outfit Ajaccio were hit with a stadium ban following the ugly scenes that marred their penalty success over Le Havre at the weekend.
Supporters of the Corsican club were accused of attacking the visiting team bus, and Ajaccio were hit with a stadium ban for the home leg of their match with Toulouse.
Ajaccio now have a mountain to climb in the second leg of the clash - which will take place on Sunday night - following a three-goal defeat to their Ligue 1 opponents.
On-loan Bournemouth attacker Max Gradel sent Toulouse ahead with a super free kick in the latter stages of a first period which was short on quality.
Toulouse then doubled their lead six minutes into the second half when Christopher Jullien half-volleyed a corner into the back of the net from close range.
Ajaccio struggled throughout the night, and they conceded a third in the 65th minute when Sanogo bundled home after the Ligue 2 outfit had failed to clear their lines - leaving Toulouse with a strong advantage ahead of the return fixture.
AJACCIO (4-2-3-1): Leca (Mandanda 46'); Hergault, Marin, Avinel, Lejeune; Boe-Kane, Camara; Nouri, Cavalli (Laci 69'), Maazou; Gimbert (Vialla 60')
TOULOUSE (4-3-3): Lafont; Yago, Diop, Jullien, Moubandje; Somalia (Mubele 76'), Sangare, Imbula Wanga; Durmaz (Toivonen 66'), Sanogo (Blin 92'), Gradel