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Chemistry. 2010 Jan 18;16(3):1033-45. doi: 10.1002/chem.200901893.

Expanding the scope of enantioselective ferroPHANE-promoted [3+2] annulations with alpha,beta-unsaturated ketones.

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  • 1Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles-CNRS UPR 2301, 1, av. de la Terrasse, 91198 Gif-sur-Yvette Cedex, France.

Abstract

The planar chiral 2-phospha[3]ferrocenophane I has been shown to be the first efficient nucleophilic organocatalyst for the enantioselective synthesis of cyclopentenylphosphonates, through [3+2] cyclizations between diethyl allenylphosphonate and alpha,beta-unsaturated ketones. The same catalyst has also been applied to the highly enantioselective [3+2] cyclizations of allenic esters with dibenzylideneacetone and analogous bis-enones, leading to functionalised cyclopentenes with either monocyclic or spirocyclic structures (ee 84-95 %). It has been shown that the residual enone functions in the resulting cyclopentenes can be involved in subsequent cyclization steps to afford unprecedented C(2)-symmetric bis-cyclopentenylketones. In order to provide insight into the behaviour of FerroPHANE I as a chiral catalyst in [3+2] cyclisations, the energetically most favoured isomers of the key phosphine-allene adduct have been calculated by DFT methods. Factors likely to control the chiral induction process are highlighted.

PMID:
19938005
[PubMed - indexed for MEDLINE]
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