Advances in Bifunctional Squaramide-Catalyzed Asymmetric Sulfa-Michael Addition: A Decade Update

Abstract

Bifunctional organocatalysts have remarkably advanced in organic chemistry owing to their high stability to moisture/air, relatively non-toxicity, ease of handling, and recoverability. Among chiral bifunctional organocatalysts, squaramides have emerged as the privileged catalyst in recent years. This review article proposes a comprehensive report on fine-tunable bifunctional chiral squaramide-catalyzed sulfa-Michael addition, which is based upon synchronous interplay of synergistic ‘electrophilicnucleophilic’ dual activation strategy via multiple H-bonding interactions for the construction of common and/or complex molecular entities bearing multiple stereocenters. Mechanistic discussions were kept only briefly, wherein significant understandings have been realized. The contribution of squaramide catalyst in the construction of C–S bond via sulfa-Michael addition has been amenable in medicinal, natural, and industrial chemistry. Attention has been paid to summarizing the progress made in chiral squaramide-catalyzed asymmetric sulfa-Michael addition and subsequent cascade/domino reaction sequences between 2011 and 2022.

Enantioselective Synthesis of Spiro Heterocyclic Compounds Using a Combination of Organocatalysis and Transition‐Metal Catalysis

“…[85][86][87][88][89][90][91] Other important types of non-covalent catalysts widely used in the asymmetric synthesis are chiral thiourea [92][93][94] and squaramide derivatives. [95][96][97] Recently, a combination of non-covalent catalysis with TM catalysis has been of high interest in stereocontrolled synthesis. Undoubtedly, it provides new opportunities in synthesizing optically pure spiro heterocycles as privileged compounds in medicinal and synthetic organic chemistry.…”

“…Over the last decade, Brønsted acid catalysis using chiral phosphoric acids has been a rapidly growing area of non‐covalent catalysis concerning the synthesis of optically pure compounds [85–91] . Other important types of non‐covalent catalysts widely used in the asymmetric synthesis are chiral thiourea [92–94] and squaramide derivatives [95–97] . Recently, a combination of non‐covalent catalysis with TM catalysis has been of high interest in stereocontrolled synthesis.…”