Notes and references § Evidence that the preferred atropoisomer has an anti arrangement comes not from the single crystal structure, rather from the observation of the nature of the NMR signal (2 x AB signals) as the syn isomer would have a plane of symmetry and so the meta-hydrogens would no longer be related as diastereotopic. † Crystal structures have been deposited at CCDC with deposition numbers 2195198-2195200.