Cross-coupling reactions usually require a functionalised aromatic or heteroaromatic ring in one component. This may require one or more synthetic step to synthesise, but usually ensures that the coupling reaction occurs in the desired position on the ring, at the position replacing that functional group. However it may be more efficient if the aromatic or heteroaromatic ring can e directly coupled.

A recent review (L Ackermann et al, Angew Chem Int Ed, 2009, 48, 9792-9826) describes progress in this field. Some example are given below: