The invention provides a the use of a (hetero)cycloalkyne and an oxo-group containing (hetero)1,3-diene for coupling a first system (A) of interest to a second system (A) of interest, wherein a (hetero)cycloalkyne is created in one of the first system (A) of interest and the second system (A) of interest, and wherein an oxo-group containing (hetero)1,3-diene is created in the other system of interest, and allowing the (hetero)cycloalkyne and the oxo-group containing (hetero)1,3-diene to react to form an A-A conjugate.