- Ruthenium-lewis acid catalyzed asymmetric diels-alder reactions between dienes and α,β-unsaturated ketones
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The complex [Ru(Cp)(R,R-BIPHOP-F)(acetone)][SbF6],(R,R)-1a. was used as catalyst for asymmetric Diels-Alder reactions between dienes (cyclopentadiene, methylcyclopentadienc, 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)-1b, and [Ru(Cp)((R,R)-Me4BIPHOP-F)(acrolein)][SbF6], (R,R)-2b, provided the basis for a rationalization of the asymmetric induction.
- Rickerby, Jenny,Vallet, Martial,Bernardinelli, Gerald,Viton, Florian,Kuendig, E. Peter
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p. 3354 - 3368
(2008/03/27)
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- New Carbonyl Compounds in the High-Boiling Fraction of Lavender Oil
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The occurrence of a series of new constituents which can be considered as Diels-Alder adducts of methyl vinyl ketone and ocimene (1-4), myrcene (9,10) or β-farnesene (11,12), respectively, was reported.Furthermore, the structures of four isomeric cyclohexene derivatives could be established as adducts 21-24 of (E,Z)- and (E,E)-1,3,5-undecatriene and methyl vinyl ketone.Another series of constituents having the norbornane skeleton represents adducts 25-32 and 33-40 of methylcyclopentadiene and octen-3-one or methyl vinyl ketone, respectively.In accordance with Alder's endo-rule the endo-isomers are preponderant in the natural as well as in the synthetic mixtures.Most of these constituents could also be identified in a lavender absolute as well as in a freshly prepared hexane extract of lavender flowers (Lavandula officinalis CHAIX).
- Kaiser, Roman,Lamparsky, Dietmar
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p. 1184 - 1197
(2007/10/02)
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