Bifunctional Squaramide‐Catalysed Asymmetric Michael/Hemiketalization/Retro‐Aldol Reaction of Unsaturated Thiazolones with α‐Nitroketones: Synthesis of Chiral 4‐Acyloxythiazole Derivatives

Abstract

An efficient and practical organocatalytic asymmetric cascade Michael/hemiketalization/retro-aldol reaction of unsaturated thiazolones with α-nitroketones by using cyclohexanediamine-derived bifunctional squaramide as the catalyst has been developed. Under mild conditions, a broad range of chiral 4acyloxythiazole derivatives were obtained in high yields (up to 98% yield) with excellent enantioselectivities (up to 95% ee). Meanwhile, a few synthetic transformations have been demonstrated.

Asymmetric Addition and Cycloaddition Reactions with Ylidene‐Five‐Membered Heterocycles

“…Du developed a synthesis of 4‐acyloxythiazole derivatives through an asymmetric cascade Michael addition/hemiketalization/retro‐aldol reaction between α‐nitroketones and 5‐arylidene‐thiazol‐4‐ones catalyzed by the bifunctional squaramide C1 7 (Scheme 109). [162] …”

Recent Advances in Catalytic Asymmetric Reactions of Thiazolones, Rhodanines and Their Derivatives

“…With the identified catalyst C50, Du et al developed a Michael-type reaction of unsaturated thiazolones 149 with α-nitroketones 150 (Scheme 44). [52] The Michael-type reaction comprised a cascade Michael/ hemiketalization/retro-aldol reaction, affording 4-acyloxythiazole derivatives 151 in 60-98% yields with 74-93% ee.…”

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

“…[14][15][16][17][18]. Other groups also contributed contemporarily [19][20][21]. In recent years 4-arylidenepyrrolidine-2,3-diones have been explored mainly for the preparation of bicyclic dihydropyran derivatives through the catalytic inverse-electrondemand hetero-Diels-Alder reaction [22][23][24].…”