TY - JOUR
T1 - Catalytic asymmetric heterogeneous aziridination of styrene using CuHY: effect of nitrene donor on enantioselectivity
AU - Taylor, Sophia
AU - Gullick, John
AU - McMorn, Paul
AU - Bethell, Donald
AU - Bulman Page, Philip C.
AU - Hancock, Frederick E.
AU - King, Frank
AU - Hutchings, Graham J.
PY - 2001
Y1 - 2001
N2 - 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.
AB - 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.
KW - OLEFINS
KW - ALKENES
KW - CHIRAL LIGANDS
KW - PORPHYRIN
KW - LIGAND-ACCELERATED CATALYSIS
KW - IODOSYLBENZENE
KW - CYCLOPROPANATION
KW - MANGANESE
KW - EPOXIDATION
KW - COMPLEXES
U2 - 10.1039/B104522A
DO - 10.1039/B104522A
M3 - Article
SP - 1714
EP - 1723
JO - Journal of the Chemical Society, Perkin Transactions 2
JF - Journal of the Chemical Society, Perkin Transactions 2
SN - 1472-779X
IS - 9
ER -