The conformation of trans-18a in which both substituents are equatorial is likely to be overwhelmingly favoured and this will make the molecule more rigid, preventing further C-H insertion steps from taking place. It is possible that trans-18a is formed via epimerisation of the intermediate palladium complex from cis-23 to trans-23 prior to the arylation reaction with the iodoarene. Similarly, monoarylation of 14 and 21 almost certainly occurs selectively due to the requirement for the directing group to be axial in order for the palladium to reach the C-3 hydrogen atom. In the products 15/22, the conformation with both substituents axial is likely to be energetically unfavourable, so no second arylation takes place.