Ruthenium-Lewis acid catalyzed asymmetric Diels-Alder reactions between dienes and alpha,beta-unsaturated ketones.
The complex [Ru(Cp)(R,R-BIPHOP-F)(acetone)][SbF(6)], (R,R)-1 a, was used as catalyst for asymmetric Diels-Alder reactions between dienes (cyclopentadiene, methylcyclopentadiene, isoprene, 2,3-dimethylbutadiene) and alpha,beta-unsaturated ketones (methyl vinyl ketone (MVK), ethyl vinyl ketone, divinyl ketone, alpha-bromovinyl methyl ketone and alpha-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. alpha-Chlorovinyl methyl ketone performed better than alpha-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)][SbF(6)], (S,S)-1 b, and [Ru(Cp)((R,R)-Me(4)BIPHOP-F)(acrolein)][SbF(6)], (R,R)-2 b, provided the basis for a rationalization of the asymmetric induction.
Rickerby
Jenny
J
Department of Organic Chemistry, Sciences II, University of Geneva, 30 Quai Ernest-Ansermet, CH1211, Geneva 4, Switzerland.
Vallet
Martial
M
Bernardinelli
Gerald
G
Viton
Florian
F
Kündig
E Peter
EP
D000466:Alkadienes / Q000737:chemistry*; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D006844:Hydrocarbons, Cyclic / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism; D014753:Vinyl Compounds / Q000737:chemistry
D000466:Alkadienes; D006844:Hydrocarbons, Cyclic; D007659:Ketones; D014753:Vinyl Compounds; D012428:Ruthenium