Solvias Ferrocenyl-Based Ligands

Aldrich ChemFiles 2006, 6.8, 12.

Aldrich ChemFiles 2006, 6.8, 12.

Solvias AG has demonstrated the incredible utility of chiral ferrocenyl diphosphine ligands in a wide range of reaction paradigms ranging from hydrogenation1 to the aldol reaction2 to hydroboration.3 For years, BINAP was considered the only ligand platform that could perform at a high-level in a wide variety of reactions. The ferrocenyl architecture in the Solvias portfolio serves as the superstructure for a unique group of chiral ligands that can be fine tuned electronically and/or sterically for asymmetric synthesis optimization. The Solvias ligands can be combined with metal precursors to form exceptionally active catalysts that exhibit high levels of enantiocontrol in industrially useful processes such as hydrogenation (Scheme 36).1 This example illustrates the high enantioselective control exerted by the Josiphos ligand on dimethyl itaconate derivative 8. The dimethyl (S)-2-methylsuccinate product was isolated in quantitative yield and with an optical purity of 99%. Also of interest to synthetic chemists is the high substrate to catalyst ratio (1000:1), while the low hydrogen pressure and fast conversion times further improve the attractiveness of this system.

Scheme 36


Feringa and co-workers have pioneered the use of the Solvias ligand family in the copper-catalyzed asymmetric conjugate addition of Grignard reagents to unsaturated carbonyl compounds.4 Prior to this group’s research, only meager selectivities had been observed in the conjugate addition of Grignard reagents, which stands in stark contrast to the success seen with the related addition of dialkylzinc reagents.5 The Feringa group utilized the Taniaphos-type ligand in conjunction with Cu(I) salts to create a highly effective catalyst system. For instance, the conjugate addition of EtMgBr to methyl cinnamate affords 96% enantiopure product at a modest 65% conversion (Scheme 37). The lower conversions in this chemistry are most likely due to the necessity of running the reaction at –78 ºC.

Scheme 37


Sigma-Aldrich, in collaboration with Solvias AG, is pleased to offer a diverse array of chiral ligands that can be ligated to metal complexes to afford highly active catalysts for asymmetric hydrogenation and other innovative transformations.6 We are excited to offer 40 different ligands and catalysts in 100 mg sample sizes in both enantiomeric forms giving you access to a total of 80 products all in one convenient kit! This kit will allow rapid screening of your asymmetric synthesis plans. Each individual ligand from the unique families below can also be ordered as individual units (Scheme 38).

Scheme 38


 

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Materials

     

References

  1. Togni, A. et al. J. Am. Chem. Soc. 1994, 116, 4062.
  2. Togni, A. et al. J. Org. Chem. 1990, 55, 1649.
  3. Togni, A. et al. Organometallics 1997, 16, 255.
  4. Feringa, B. L. et al. J. Am. Chem. Soc. 2006, 128, 9103.
  5. (a) Lippard, S. J. et al. J. Am. Chem. Soc. 1988, 110, 3175. (b) Lippard, S. J. et al. Organometallics 1990, 9, 3178. (c) van Koten, G. et al. J. Am. Chem. Soc. 1992, 114, 3400. (d) Pfaltz, A. et al. Tetrahedron 1994, 50, 4467. (e) Seebach, D. et al. Angew. Chem., Int. Ed. 2000, 39, 153. (f) Tomioka, K. et al. Tetrahedron Lett. 1998, 54, 10295. (g) Sammakia, T. et al. Tetrahedron 1997, 53, 16503.
  6. Solvias ligands and kit are sold in collaboration with Solvia, AG. for research purposes only.

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