New enantiopure binaphthyl-cinchona thiosquaramides: synthesis and application for enantioselective organocatalysis. (27th March 2019)

• Record Type: Journal Article
• Authors: Nagy, Sándor; Dargó, Gyula; Kisszékelyi, Péter; Fehér, Zsuzsanna; Simon, András; Barabás, Júlia; Höltzl, Tibor; Mátravölgyi, Béla; Kárpáti, Levente; Drahos, László; Huszthy, Péter; Kupai, József
• Is Part Of: New journal of chemistry. Volume 43:Number 15(2019)
• Page Start: 5948
• Page End: 5959
• Publication Date: 2019-03-27
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c8nj06451b
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Binaphthyl-cinchona squaramide and thiosquaramide were applied as organocatalysts in three types of asymmetric reactions with excellent yields and enantioselectivities. 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.