On the enantioselectivity of aziridination of styrene catalysed by copper triflate and copper-exchanged zeolite Y: consequences of the phase behaviour of enantiomeric mixtures of N-arene-sulfonyl-2-phenylaziridines

Jeffs, Laura E., Arquier, Damien, Kariuki, Benson ORCID: https://orcid.org/0000-0002-8658-3897, Bethell, Donald, Page, Philip C. Bulman and Hutchings, Graham John ORCID: https://orcid.org/0000-0001-8885-1560 2011. On the enantioselectivity of aziridination of styrene catalysed by copper triflate and copper-exchanged zeolite Y: consequences of the phase behaviour of enantiomeric mixtures of N-arene-sulfonyl-2-phenylaziridines. Organic & Biomolecular Chemistry 9 (4) , pp. 1079-1084. 10.1039/c0ob00724b

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Abstract

By synthesising S-2-phenyl-N-(4-nitrophenyl)aziridine from S-phenylglycinol, it has been demonstrated that the aziridination of styrene by [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane (nosyliminophenyliodinane, PhINNs) in the presence of S,S-2,2′-isopropylidene-bis(4-phenyl-2-oxazoline), catalysed by copper(II) triflate in CH3CN solution or heterogeneously by CuHY, has predominantly an R-configuration. The enantioselectivity of the aziridination of styrene by [N-arenesulfonylimino]-phenyliodinanes catalysed by copper-exchanged zeolite Y (CuHY), in conjunction with a chiral bis-oxazoline ligand, has been re-examined. In the case of PhINNs, it is shown that the product mixture of enantiomeric aziridines, on treatment with hexane, gives rise to a solid phase of low enantiomeric excess (ee) and a solution phase of high ee. Separation of the solid phase and recrystallisation afforded a true racemate (racemic compound), which has been confirmed by X-ray crystallography. The aziridine obtained from the solution phase could be recrystallised to produce the pure enantiomer originally in excess. A consequence of the new findings is that previous reports on the enantioselectivity of copper-catalysed aziridination, both in heterogeneous and homogeneous conditions, should be regarded with caution if the analytical procedure involved HPLC with injection of the enantiomeric mixture in a hexane-rich solvent. Such a method has been used in previous work from this laboratory, but has also been used elsewhere, following the procedure developed by Evans and co-workers when the (homogeneous) copper-catalysed aziridination by PhINTs was first discovered. Evidently, the change of substituent in the benzenesulfonyl group reduces the solubility in hexane, affording a solution phase of enhanced ee.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Cardiff Catalysis Institute (CCI) Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	RSC
ISSN:	1477-0520
Last Modified:	18 Oct 2022 13:14
URI:	https://orca.cardiff.ac.uk/id/eprint/13134

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