Associate Functionality Using Dynamic 365 For Entities in an N:N relationship

Question

I was working on a use case where I have two entities salesorder and account of Microsoft Dynamic 365 with which I need to perform associate functionality . These entities are present in an N:N relationship.
Do we have any Rest API call to achieve the same in dynamic 365. (Like Rest API call which includes call to dynamic 365 organization specific url , the two entities and their specific Id) . Note that N:N related entities do not have any field to bind the two.
If we have such Rest call for associate kindly provide with example . O r if we do not have any such functionality how to procced with the same.