Recent Advances in Phosphonium Salt Catalysis

Abstract

Quaternary phosphonium salts have been extensively used in organic synthesis as Lewis acid organocatalysts. This review covers recent applications of phosphonium salts as Lewis acidic catalysts for Mannich, Strecker, and Friedel‐Crafts reactions for the formation of C−C bonds, annulation reactions, etc., allowing the construction of structurally diverse and synthetically useful architectures.

Access to S-Stereogenic Free Sulfoximines via Bifunctional Phosphonium Salt-Catalyzed Desymmetrization of Bisphenols

“…Of note, the great challenge in such asymmetric desymmetrizing A–T process lies in not only the difficult stereodifferentiation between the two aryl rings when attaching the P-species to their hydroxyl groups, but also the competitive sites between the free N-H on the S-center and free O–H on the aryl ring for the chemoselective coupling reaction. Furthermore, the past few years have witnessed our great progress in bifunctional phosphonium salts , and their applications in a wide spectrum of catalytic asymmetric transformations. , Based on this, we reasoned that such highly tunable bifunctional phosphonium salt catalysts could offer the opportunity to solve the stereo- and chemoselectivity and reactivity issues of the desymmetrizing A–T reaction and the related transformation. In response to this assumption, herein, we presented the first catalytic protocol to construct chiral free N-H sulfoximines via a bifunctional phosphonium salt-catalyzed desymmetrizing A–T-type reaction together with the extended nucleophilic acyl substitution-type (NAS-type) reaction (Figure C).…”

Asymmetric Construction of Tertiary/Secondary Carbon–Phosphorus Bonds via Bifunctional Phosphonium Salt Catalyzed 1,6-Addition

“…On the basis of our disclosure of dipeptide-based phosphonium salts and their utilities in asymmetric synthesis, − we hypothesized that these bifunctional cationic phosphonium catalysts, which have semienclosed cavities and remarkable electrostatic potential (ESP) bearing an electropositive area (Figure c), would be effective for stabilizing the anionic phosphorus species through an H-bonding interaction between the oxygen atom of the P-nucleophile and phosphonium salt’s Brønsted acid moiety, together with ion-pair activation offered by the cationic phosphonium core, thus leading to the expected remote C–P formation; moreover, the simultaneous introduction of a side group (SG) such as cyano into the δ-position of the conjugated π-system would assist in improving the chiral induction (Figure d, the former). The successful implementation of this strategy would provide an expedient access to previously challenging chiral scaffolds bearing tertiary/secondary C–P bonds with quatarnary diarylacetonitrile units, both of which represent important building blocks in organic synthesis together with broad biomedical applications. , However, significant challenges are anticipated in exploring this asymmetric remote C–P bond formation (Figure d, the latter).…”

Asymmetric synthesis of N-bridged [3.3.1] ring systems by phosphonium salt/Lewis acid relay catalysis

“…In this context, asymmetric organocatalysis that greatly enhances the synthetic toolbox by complementing metal-based and enzymatic methodologies offers powerful solutions to this endeavor 26 , which is conducive to expanding the diversity of chiral molecules for modulating biological targets, thus providing more opportunities for drug discovery and development 27 . Among the well-known asymmetric organocatalytic systems, asymmetric phase-transfer catalysis (PTC) 28 particularly involving phosphonium salts as catalysts provide a powerful and versatile tool for the enantioselective synthesis of diverse chiral molecules [29][30][31][32] . The groups of Maruoka, Ooi, and Zhao have pioneered to make significant contributions in this field [33][34][35][36][37] .…”