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ChiralQuest Phosphines

By: Professor Xumu Zhang, chemfiles volume 5 article 4

Professor Xumu Zhang at Penn State has made remarkable advances by creating a toolbox of chiral phosphines which can be used on a variety of substrates, some of which have been historically resistant to facile hydrogenation. Furthermore, an additional benefit in some reductions is reduced catalyst loading, due to increased turnover numbers (TON). Sigma-Aldrich is pleased to announce an agreement with ChiralQuest to distribute research quantities of a series of Zhang’s chiral phosphines for catalytic asymmetric hydrogenations.1

(S)-C3-TunePhos

C3-TunePhos, a member of the atropisomeric aryl bisphosphine ligand family with tunable dihedral angles, provides comparable or superior enantioselectivities and catalytic abilities to BINAP in Ru-catalyzed asymmetric hydrogenations of b-keto esters (Scheme 3),2 cyclic b-(acylamino)acrylates (Scheme 4),3 and a-phthalimide ketones (Scheme 5).10


Scheme 3


Scheme 4


Scheme 4

(1S,1S’,2R,2R’)-TangPhos

A highly electron-donating, low molecular weight, and rigid P-chiral bisphospholane ligand, TangPhos proves highly efficient in the rhodium-catalyzed hydrogenation of a variety of functionalized olefins such as α-dehydroamino acids (Scheme 6) and α-arylenamides (Scheme 7),5 β-(acylamino)acrylates (Scheme 8),6 itaconic acids (Scheme 9), and enol acetates (Scheme 10).7


Scheme 6


Scheme 7


Scheme 8


Scheme 9


Scheme 10

(S)-Binapine

(S)-Binapine, a highly electron-donating rigid ligand, demonstrates excellent enantioselectivity and reactivity, with TON up to 10,000 for the asymmetric hydrogenation of Z-β-aryl(β-acylamino)acrylates (Scheme 11).8


Scheme 11

(R)-Binaphane

(R)-Binaphane shows excellent enantioselectivity (up to >99% ee) for hydrogenation of E/Z-isomeric mixtures of β-substituted arylenamides (Scheme 12).9


Scheme 12

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References

  1. For an excellent review, see: Tang, W.; Zhang, X. Chem. Rev. 2003, 103, 3029.
  2. Zhang, Z. et al. J. Org. Chem. 2000, 65, 6223.
  3. Tang, W. et al. J. Am. Chem. Soc. 2003, 125, 9570.
  4. Lei, A. et al. J. Am. Chem. Soc. 2004, 126, 1626.
  5. Tang, W.; Zhang, X. Angew. Chem., Int. Ed. Engl. 2002, 41, 1612.
  6. Tang, W.; Zhang, X. Org. Lett. 2002, 4, 4159.
  7. Tang, W. et al. Org. Lett. 2003, 5, 205.
  8. Tang, W. et al. Angew. Chem., Int. Ed. Engl. 2003, 42, 3509.
  9. Xiao, D. et al. Org. Lett. 1999, 1, 1679.

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