Catalytic asymmetric heterogeneous aziridination of styrene using CuHY: effect of nitrene donor on enantioselectivity

Taylor, Sophia, Gullick, John, McMorn, Paul, Bethell, Donald, Bulman Page, Philip C., Hancock, Frederick E., King, Frank and Hutchings, Graham J. (2001) Catalytic asymmetric heterogeneous aziridination of styrene using CuHY: effect of nitrene donor on enantioselectivity. Journal of the Chemical Society, Perkin Transactions 2 (9). pp. 1714-1723. ISSN 1472-779X

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Abstract

The copper-catalysed aziridination of styrene with copper-exchanged zeolite Y (CuHY) and copper(II) triflate (trifluoromethanesulfonate) (Cu(OTf)(2)) as catalysts is described in detail. Two nitrene donors, [N-(p-tolylsulfbnyl)-imino)]phenyliodinane (PhI=NTs) and [N-(p-nitrophenylsulfonyl)imino]phenyliodinane (PhI=NNs) are compared. Modification of the catalyst with bis(oxazolines) affords enantioselective catalysts and a range of chiral bis(oxazolines) has been studied. The ratio of nitrene donor to styrene is shown to bean important factor controlling, both the yield and ee of aziridine formed. The best results are obtained with PhI=NNs;ee, greater than or equal to 90%, together with high yields (greater than or equal to 85%), can readily be achieved with this nitrene donor using acetonitrile as solvent. Addition of the nitrene donor over a period of time, rather than all at the start of the reaction, is shown to enhance the yield of the aziridine but the ee is significantly decreased for both the homogeneous and the heterogeneous catalysts. Experiments in which the breakdown products of the nitrene donor, iodobenzene and the corresponding sulfonamide, are added at the start of the reaction show that a complex interplay exists at the copper active site between the reactants, products, chiral modifier and the solvent. However, the heterogeneous catalyst, CuHY, is found to give enhanced enantioselection for a range of bis(oxazolines) compared to the homogeneous catalyst, and the effect is considered to be due to the confinement of the catalyst within the micropores of the zeolite.

Item Type:	Article
Uncontrolled Keywords:	olefins,alkenes,chiral ligands,porphyrin,ligand-accelerated catalysis,iodosylbenzene,cyclopropanation,manganese,epoxidation,complexes
Faculty \ School:	Faculty of Science > School of Chemistry (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Groups > Synthetic Chemistry (former - to 2017) Faculty of Science > Research Groups > Chemistry of Materials and Catalysis
Depositing User:	Rachel Smith
Date Deposited:	21 Jun 2011 11:26
Last Modified:	24 Sep 2024 10:25
URI:	https://ueaeprints.uea.ac.uk/id/eprint/32831
DOI:	10.1039/B104522A

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