An 18-year-old man was punched in the face by a thief wearing brass knuckles and robbed when he agreed to exchange cash and a pair of sneakers for a new cell phone, police sources said.

The teen was at the 174th Street station in Crotona Park along the 2 and 5 train lines when he agreed to trade $200 and a pair of Air Jordan sneakers for an iPhone 6 around 10:30 p.m.Sunday.

That’s when the suspect socked the victim in the mouth with the brass knuckles and stole the shoes and $100 of the man’s money.

The victim attempted to chase the suspect down Bryant Avenue before losing sight of him, police said.

The suspect is described as being in his late teens or early 20s.