Yiadom rejoined the Serbian giants before the transfer window shut at the end of last month but had to wait after the international break to make his second debut.
In the 33rd minute, Boakye opened the scoring when he shot from inside the box.
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Three minutes before the break, Marko Marin doubled the lead and in the 53rd minute Jonathan Cafu made it three-nil.
Boakye grabbed his personal second after shooting from inside the area into the roof.
Goran Causic and Nikola Stojiljkovic scored the remaining two goals.