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Issue 15, 2019
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New enantiopure binaphthyl-cinchona thiosquaramides: synthesis and application for enantioselective organocatalysis

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Abstract

This work presents the first successful applications of cinchona-thiosquaramides in asymmetric reactions. Binaphthyl-cinchona squaramides and thiosquaramides were synthesised, and then used as organocatalysts to promote the catalytic enantioselective Michael addition reaction of pentane-2,4-dione to trans-β-nitrostyrene with excellent yields (up to 99%) and enantioselectivities (up to 99% ee) at as low as 0.2 mol% catalyst loadings. Thiosquaramides gave higher enantioselectivities (up to 92% ee) in conjugate addition reaction of lawsone to β,γ-unsaturated α-keto ester than its oxo analogue, with high yields (up to 100%). Also, only thiosquaramide could catalyse the aza-Diels–Alder addition reaction of 2-siloxydiene to benzylideneacetone. Furthermore, quantum chemical computations showed that the geometrical structure of binaphthyl-cinchona thiosquaramide is similar to that of squaramide.

Graphical abstract: New enantiopure binaphthyl-cinchona thiosquaramides: synthesis and application for enantioselective organocatalysis

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Supplementary files

Article information


Submitted
21 Dec 2018
Accepted
20 Mar 2019
First published
21 Mar 2019

This article is Open Access

New J. Chem., 2019,43, 5948-5959
Article type
Paper

New enantiopure binaphthyl-cinchona thiosquaramides: synthesis and application for enantioselective organocatalysis

S. Nagy, G. Dargó, P. Kisszékelyi, Z. Fehér, A. Simon, J. Barabás, T. Höltzl, B. Mátravölgyi, L. Kárpáti, L. Drahos, P. Huszthy and J. Kupai, New J. Chem., 2019, 43, 5948
DOI: 10.1039/C8NJ06451B

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