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Catalytic Asymmetric Heterogeneous Aziridination Using CuHY/bis(oxazoline): Effect of Reaction Conditions on Enantioselectivity |
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| Authors: | Sophia Taylor John Gullick Natasha Galea Paul McMorn Donald Bethell Philip C Bulman Page Frederick E Hancock Frank King David J Willock Graham J Hutchings |
| Affiliation: | 1. Department of Chemistry, Cardiff University, P.O. Box 912, Cardiff, CF10 3TB, UK 2. Leverhulme Centre for Innovative Catalysis, Department of Chemistry, University of Liverpool, Liverpool, L69 3BX, UK 3. Department of Chemistry, Loughborough University, Loughborough, Leics, LE11 3TU, UK 4. Synetix, P.O. Box 1, Teeside, TS23 1LB, UK |
| Abstract: | The copper-catalyzed aziridination of styrene with copper-exchanged zeolite HY (CuHY) and copper(II) triflate (trifluoromethanesulfonate) (Cu(OTf)2) as catalysts is described using N-(p-tolylsulfonyl)imino]phenyliodinane (PhI=NTs) as the nitrene donor. The effects on the ee and yield of the aziridine when the catalyst is modified by the presence of a chiral bis(oxazoline) are investigated in detail. The heterogeneously catalyzed reaction under these conditions shows a slight, but significant, enhancement in ee with increasing conversion at 25 °C. This is not observed in the more rapid homogeneously catalyzed reaction under identical reaction conditions using PhINTs as the nitrene donor. The enhancement in ee is proposed to result from the preferential reaction of the (S)-aziridine with the Cu2+:bis(oxazoline) complex in the presence of PhI=NTs, leading to an enhancement of the (R)-aziridine in the remaining aziridine product. |
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