Using chiral ionic liquid additives to enhance asymmetric induction in a Diels-Alder reaction
P Goodrich1, H Q Nimal Gunaratne1, L Hall1
1School of Chemistry and Chemical Engineering/QUILL, Queen's University, Stranmillis Road, Belfast, Northern Ireland BT9 5AG, UK. p.goodrich@qub.ac.uk m.j.muldoon@qub.ac.uk.
Abstract:
A bis-oxazoline ligand has been complexed using Cu(ii) and Zn(ii) trifluoromethanesulfonate and a range of chiral ionic liquid (CIL) additives based on natural products were used as a co-catalyst for a Diels-Alder reaction. The catalytic performance of these systems was compared for the asymmetric Diels-Alder reaction between N-acryloyloxazolidinone and cyclopentadiene with and without the presence of a CIL additive. In the absence of the CIL, both catalysts resulted in low enantioselectivities in conventional solvents and ionic liquids. However, whilst only a minor effect of the CIL was observed for the Cu based catalyst, in the case of the Zn based catalyst, significant enhancements in endo enantioselectivity of up to 50% were found on the addition of a CIL.
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