Unable to map option sets

Hi 

I have 2 entities A and B and 4 option sets for each. 

Option Sets are Global.

I am unable to map these option set values via Workflow from Entity A to Entity B. 

I have tried to set the mapping via 1:N relationship from A to B and that doesnt work either as B is created via workflow from A. 

How can i map these option sets?

Thank you

Elsa