Enantioselective palladium-catalyzed addition of 1,3-dicarbonyl compounds to an allene derivative
Research output: Contribution to journal › Research article › Contributed › peer-review
Contributors
Abstract
Enhancing atom economy of the metal-catalyzed asymmetric allylic alkylation (AAA) shifts from the usual nucleophilic displacement of a leaving group to an addition of a pronucleophile to a double bond. Using 1-alkoxyallenes as proelectrophiles, the palladium-catalyzed AAA proceeds with 1,3-dicarbonyl compounds as pronucleophiles with excellent regioselectivity and enantiomeric excess under optimized conditions. The pH of the medium proved crucial for reactivity/selectivity. By using the more acidic Meldrum's acids, the reactions required a co-catalytic amount of Brønsted acid, such as trifluoroacetic acid. Single regioisomeric products of 82-99% ee were obtained. On the other hand, the less acidic 1,3-diketones failed to react under such conditions. The fact that a less acidic acid like benzoic acid sufficed, suggested the need for general base catalysis as well. Thus, a mixture of triethylamine and benzoic acid proved optimal (ee's 93-99). Employment of the (R,R)-phenyl Trost ligand gave a product with S configuration. A model to rationalize the results has been developed.
Details
Original language | English |
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Pages (from-to) | 7075-7082 |
Number of pages | 8 |
Journal | Chemistry - A European Journal |
Volume | 11 |
Issue number | 23 |
Publication status | Published - 15 Nov 2005 |
Peer-reviewed | Yes |
Externally published | Yes |
External IDs
PubMed | 16196061 |
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ORCID | /0000-0001-8423-6173/work/161891590 |
Keywords
ASJC Scopus subject areas
Keywords
- Alkylation, Allylic compounds, Asymmetric catalysis, Palladium, Proelectrophiles, Pronucleophiles