Achiral Cp*Rh(III)/Chiral Lewis Base Cooperative Catalysis for Enantioselective Cyclization via C–H Activation

Abstract

An enantioselective [4+3] cyclization via C­(sp2)–H activation with a cooperative catalytic system consisting of a Cp*Rh­(III) complex and a chiral Lewis base is described. An α,β-unsaturated acyl ammonium intermediate is generated from a chiral isochalcogenurea catalyst and an acyl fluoride reacts with a metallacycle generated from the Cp*Rh catalyst and a benzylamine derivative. This cooperative catalytic system gives a variety of benzolactams in good yields with excellent enantioselectivities (up to 99:1 er). The results demonstrated that chiral Lewis base catalysis is a powerful tool for controlling the enantioselectivity of transition metal-catalyzed C–H functionalizations.

Three-Component Chemo-Selective Synthesis of N-(o-Alkenylaryl) Pyrazoles by Pyrazole Annulation and Rh-Catalyzed Chemo-Selective Aryl C–H Addition Cascade

“…Achieving a target product with minimum synthetic operation saves not only working time but also the bulky consumption of chemicals resulting from intermediate purification. − Meanwhile, controlling the selectivity of a reaction constitutes the longstanding goal of chemical synthesis. − Although recent years have witnessed drastic advances in both step economical and selectivity tunable organic synthesis, developing more reactions by one-step construction of molecular complexity and disclosing the unconventional reaction selectivity associated with the designation of step economical reaction fashion is yet an issue of challenge. For example, as well-recognized powerful tools, the Rh-catalyzed C–H activation reactions have been proven to be highly reliable protocols in the synthesis of numerous organic compounds by the Rh insertion into inert C–H bond under the assistance of a coordinative directing group (DG); − the general requirement of a substrate containing such coordination structure, however, requires additional operation, which undermines the step efficiency of these Rh-catalyzed C–H activation reactions. Accordingly, searching for an alternative tactic of Rh-catalyzed C–H bond transformation without relying on a separately installed directing structure is highly demanding.…”

Cooperative Isothiourea/Iridium-Catalyzed Asymmetric Annulation Reactions of Vinyl Aziridines with Pentafluorophenyl Esters

“…Recently, chiral isothioureas (ITUs) have been shown to serve as effective Lewis base catalysts combined with transition metals in the discovery of new reaction manifolds and the development of elegant asymmetric processes (Scheme C) . Since the seminal work established by the Snaddon group in 2016, the discovery of efficient ITU/TM cooperative catalytic systems to access chiral molecules continues to attract the attention of organic chemists, and many achievements have been accomplished. − Since 1997, the development of iridium-catalyzed asymmetric allylic substitution reactions has emerged as a powerful methodology for the construction of complex molecules or natural products . In 2021, we disclosed that the iridium catalyst and N-heterocyclic carbene organocatalyst could be merged in the [4 + 3] annulation reaction involving vinyl aziridines .…”

Palladium-Catalyzed [5 + 2] Rollover Annulation of 1-Benzylpyrazoles with Alkynes: A Direct Entry to Tricyclic 2-Benzazepines

“…In recent years, more sustainable approaches based on intermolecular metal-catalyzed cycloadditions involving the direct activation of C–H bonds (oxidative annulations) have strongly emerged to build up medium-sized heterocycles . Thus, for 2-benzazepin­(on)­es, Glorius, Matsunaga/Yoshino, and Cui independently developed a convergent Rh-catalyzed [4 + 3] cycloaddition between benzamides and α,β-unsaturated carbonyls or vinylcarbenoids (Scheme a). Besides, Kim developed a Rh-catalyzed [4 + 3] cycloaddition between N -allyl benzylamines and allyl derivatives (Scheme a) .…”