Chiral Cationic Cp(x)Ru(II) Complexes for Enantioselective Yne-Enone Cyclizations
David Kossler1, Nicolai Cramer1
1Laboratory of Asymmetric Catalysis and Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
Journal of the American Chemical Society
|September 17, 2015
Summary
Chiral cyclopentadienyl ruthenium(II) complexes catalyze yne-enone cyclizations efficiently. This method rapidly produces pyrans with high enantioselectivity, yielding iridoid skeletons from unsaturated esters or Weinreb amides.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Organic Synthesis
Background:
- Cyclopentadienyl (Cp) ligands are crucial in transition-metal catalysis.
- Cationic CpRu(II) complexes offer versatile catalytic applications due to available coordination sites.
Purpose of the Study:
- Synthesize novel CpRu(II) complexes featuring chiral Cp ligands.
- Maximize available coordination sites for enhanced catalytic activity.
- Investigate their efficiency and selectivity in yne-enone cyclizations.
Main Methods:
- Synthesis of a new family of Cp(x)Ru(II) complexes with chiral Cp ligands.
- Utilizing these cationic complexes as catalysts.
- Performing formal hetero-Diels-Alder reactions (yne-enone cyclizations).
Main Results:
- The cationic CpRu(II) complexes are efficient and selective catalysts.
- Yne-enone cyclizations proceed rapidly (<1 hour at -20 °C).
- Pyrans are formed with high enantiomeric ratios (up to 99:1 er).
- Iridoid skeletons are directly obtained from unsaturated ester or Weinreb-amide substrates.
Conclusions:
- Chiral CpRu(II) complexes represent valuable catalysts for atom-economic transformations.
- The developed method offers a highly enantioselective route to pyrans and iridoid skeletons.
- This work expands the utility of CpRu(II) complexes in asymmetric catalysis.
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