(-)-sparteine-mediated metalation of ferrocenesulfonates. The first case of double asymmetric induction of ferrocene planar chirality

[GRAPHICS] A new process for induction of planar chirality via a matched chiral-directed metalation group (DMG)/(-)-sparteine interaction is demonstrated. Thus, s-BuLi metalation of (-)-menthylferrocenesulfonate (8b) with (-)-sparteine constitutes a matched pair resulting in amplification of the dr in the 2-formyl product 10a.