Ruthenium-Lewis Acid Catalyzed Asymmetric Diels-Alder Reactions between Dienes and α,β-Unsaturated Ketones

The complex [Ru(Cp)(R,R‐BIPHOP‐F)(acetone)][SbF6], (R,R)‐1 a, was used as catalyst for asymmetric Diels–Alder reactions between dienes (cyclopentadiene, methylcyclopentadiene, isoprene, 2,3‐dimethylbutadiene) and α,β‐unsaturated ketones (methyl vinyl ketone (MVK), ethyl vinyl ketone, divinyl ketone,...

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Bibliographic Details
Published in:Chemistry : a European journal 2007-01, Vol.13 (12), p.3354-3368
Main Authors: Rickerby, Jenny, Vallet, Martial, Bernardinelli, Gerald, Viton, Florian, Kündig, E. Peter
Format: Article
Language:English
Subjects:
Alkadienes - chemistry
asymmetric catalysis
Catalysis
Combinatorial Chemistry Techniques
Diels-Alder reactions
dienophiles
Hydrocarbons, Cyclic - chemistry
Ketones - chemistry
Lewis acids
Molecular Structure
ruthenium
Ruthenium - chemistry
Stereoisomerism
Vinyl Compounds - chemistry
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Summary:The complex [Ru(Cp)(R,R‐BIPHOP‐F)(acetone)][SbF6], (R,R)‐1 a, was used as catalyst for asymmetric Diels–Alder reactions between dienes (cyclopentadiene, methylcyclopentadiene, isoprene, 2,3‐dimethylbutadiene) and α,β‐unsaturated ketones (methyl vinyl ketone (MVK), ethyl vinyl ketone, divinyl ketone, α‐bromovinyl methyl ketone and α‐chlorovinyl methyl ketone). The cycloaddition products were obtained in yields of 50–90 % and with enantioselectivities up to 96 % ee. Ethyl vinyl ketone, divinyl ketone and the halogenated vinyl ketones worked best and their reactions with acyclic dienes consistently provided products with >90 % ee. α‐Chlorovinyl methyl ketone performed better than α‐bromovinyl methyl ketone. The reaction also provided a [4.3.1]bicyclic ring system in 95 % ee through an intramolecular cycloaddition reaction. Crystal structure determinations of [Ru(Cp)((S,S)‐BIPHOP‐F)(mvk)][SbF6], (S,S)‐1 b, and [Ru(Cp)((R,R)‐Me4BIPHOP‐F)(acrolein)][SbF6], (R,R)‐2 b, provided the basis for a rationalization of the asymmetric induction. A one‐point binding transition metal Lewis acid catalyst capable of coordinating and activating α,β‐unsaturated ketones for enantioselective Diels–Alder reactions has been developed. The asymmetric induction ranges from modest to excellent. The catalyst is capable of operating effectively in both syn (shown in figure) and the more usual anti–s‐trans orientations for asymmetric Diels–Alder reactions.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.200600851