Constraining asymmetric organometallic catalysts within mesoporous supports boosts their enantioselectivity.
By constraining tethered asymmetric organometallic catalysts within the nanopores of silica supports so as to increase the interaction between the pore wall and the active center (and hence to restrict access of the reactant to the catalyst), a significant improvement in enantioselectivity is achieved. A schematic illustration of a cationic chiral, organometallic catalyst, [Rh(I)(COD)PMP] {(S)-(+)-1-(2-pyrrolidinylmethyl)-pyrrolidine and cyclooctadiene}, which is noncovalently anchored via a N-H...F hydrogen bond with the triflate ion, CF3SO3-, to the curved inner surface of a 38 A diameter pore of a silica support for the asymmetric hydrogenation of the C=O bond in methyl benzoylformate to the corresponding methyl mandelate is shown. Rh (purple); N (blue); H (white); F (green); C (gray); S (yellow); O (red).
Raja
Robert
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Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albemarle Street, London, UK.
Thomas
John Meurig
JM
Jones
Matthew D
MD
Johnson
Brian F G
BF
Vaughan
David E W
DE