Synthesis of a biferrocene diphosphine ligand with only planar chirality and its application in the Rh-catalyzed asymmetric hydrogenation of β-keto sulfones

A new type of biferrocene diphosphine ligand bearing only planar chirality was developed and used in Rh(I)-catalyzed asymmetric hydrogenation of β-keto sulfones, giving the corresponding optically active β-hydroxy sulfones in excellent yields and in 72.4–97.9% ee.

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(S)-p-TolylsulfinylferroceneC17H16FeOS[α]D20=+314(c0.525,CHCl3)Source of chirality: (−)-menthol

(SFc,SS)-1-p-Tolylsulfinyl-2-(diphenylphosphino)ferrocene borane complexC29H28BFeOPS[α]D20=-533(c0.545,CHCl3)Source of chirality: (−)-menthol

(R)-2-Diphenylphosphino-ferrocenecarboxaldehyde borane complexC23H22BFeOPS[α]D20=-556(c0.2,CHCl3)Source of chirality: (−)-menthol

(R,R)-Bis[2-(diphenylphosphino)ferrocenyl]methanolC45H38Fe2OP2[α]D20=+400(c0.215,CHCl3)Source of chirality: (−)-menthol