Sanchez broke the deadlock for Arsenal in the 63rd minute after a fine passing exchanges between Chamberlain and Welbeck saw the Chilean forward score his sixth goal in the last four appearances for Arsenal.
Arsenal who lost a three goal lead in midweek against Anderlecht, saw their lead cut short by a beautifully curled free-kick by Gulfyi Sigurdsson, with quarter an hour to go. Substitute Gomis took just two minutes to head home Swansea's winner two minutes after the equalizer to condemn Arsenal to their second loss of the loss.
Newcastle continued their excellent form with a 0-2 away win at West Bromwich Albion, to make it four successive league games for the first time since November 2013. Perez opened the scoring on the stroke of half-time with a sublime backheel from 12 yards out.
The game was ended as a contest on 62 minutes when an unmarked Coloccini headed in at the far post.
Everton survived a scare after full back scored from the spot Leighton Baines scored from the penalty spot to salvage a 1-1 draw away at Sunderland.
The Black Cats had taken the lead when Sebastian Larsson curled in a free-kick after Baines had fouled Will Buckley.
But England defender Baines made amends with a spot-kick following Connor Wickham's rash challenge on Seamus Coleman inside the box.
In other results: Stoke shocked 12th placed Tottenham with a 1-2 rare win.
-BBC