Arsenal had come into the game missing Jack Wilshere who was out due to illness and needed to beat Anderletch, and also Dortmund to defeat Galatassary in the other group encounter to secure qualification.
The Gunners had begun the game in fast tempo hoping to score immediately off the mark but the Belgian team kept their discipline and almost had the game opener at the 17th minute mark.
At the 24th minute, Arteta slotted in a penalty after Welbeck was brought down in the box.
By the 28th minute, Sanchez scored his 11th goal in 13 games when he smashed in a deflected free kick.On the second half, Alex Oxlade chamberlain broke off his defender, and slotted the ball home to make it
3-0.
Then it all came tumbling down with Arteta going off injured and then Anderletch big man Anthony Vanden Borre scored a tap in while in an offside position.
Vaden Borre then scored again, this time through a penalty after Mitrovic was brought down by Nacho Monreal in the box.
And as the game ticked off, The Serbian Mitrovic struck again as he sped past a slow Mertesacker and nodded the ball past Sczesny on the 89th minute.
Meanwhile in the other game, Dortmund beat Galatassary by 4-1, securing Qualification to the second round of the tournament
source; naij