Sky sources understand that Arsenal are 'very confident' of signing the Chile international striker for around £30m.
Sanchez has reportedly turned down offers from Liverpool and Juventus, telling his representatives a move to the Emirates is his preferred destination.
Barcelona are believed to have bowed to Sanchez's request to move to London rather than Liverpool, where he could have been used as a makeweight in a potential deal for Luis Suarez.
Should the deal come off, he will become Arsenal's second most-expensive signing following the £42.5m capture of Mesut Ozil from Real Madrid last September.
Full-back Debuchy, meanwhile, is set to join the club for around £10m in the next 48 hours as boss Arsene Wenger attempts to fill the void left by the departure of Bacary Sagna to Manchester City.
Debuchy was preferred to Sagna by France boss Didier Deschamps throughout the World Cup. Debuchy, 28, has played 46 appearances for Newcastle, scoring once, since moving to the club from Lille for £5.5m in January 2013.
A defensive midfielder is also said to be on Wenger's wanted list, with Lars Bender of Bayer Leverkusen reportedly a long-term target.
Arsenal also released several players at the end of their contracts, including striker Nicklas Bendtner.
The Denmark forward has several options, reported to be both from within the Premier League as well as European sides.
Arsenal step up their pre-season schedule in New York at the end of the month ahead of hosting the Emirates Cup and the FA Community Shield against Manchester City at Wembley on August 10.