Rh(II)/Brønsted Acid Catalyzed General and Highly Diastereo- and Enantioselective Propargylation of in Situ Generated Oxonium Ylides and C-Alkynyl N-Boc N,O-Acetals: Synthesis of Polyfunctional Propargylamines

Controlling Stereoselectivity with Noncovalent Interactions in Chiral Phosphoric Acid Organocatalysis

Chiral phosphoric acids (CPAs) have emerged as highly effective Brønsted acid catalysts in an expanding range of asymmetric transformations, often through novel multifunctional substrate activation modes. Versatile and broadly appealing, these catalysts benefit from modular and tunable structures, and compatibility with additives. Given the unique types of noncovalent interactions (NCIs) that can be established between CPAs and various reactants─such as hydrogen bonding, aromatic interactions, and van der Waals forces─it is unsurprising that these catalyst systems have become a promising approach for accessing diverse chiral product outcomes. This review aims to provide an in-depth exploration of the mechanisms by which CPAs impart stereoselectivity, positioning NCIs as the central feature that connects a broad spectrum of catalytic reactions. Spanning literature from 2004 to 2024, it covers nucleophilic additions, radical transformations, and atroposelective bond formations, highlighting the applicability of CPA organocatalysis. Special emphasis is placed on the structural and mechanistic features that govern CPA-substrate interactions, as well as the tools and techniques developed to enhance our understanding of their catalytic behavior. In addition to emphasizing mechanistic details and stereocontrolling elements in individual reactions, we have carefully structured this review to provide a natural progression from these specifics to a broader, class-level perspective. Overall, these findings underscore the critical role of NCIs in CPA catalysis and their significant contributions to advancing asymmetric synthesis.

HFIP-mediated cascade aminomethylation and intramolecular cyclization of allenamides with N,O-acetals to access tetrahydro-β-carboline derivatives

The construction of complex molecules under metal-free conditions via multiple bond-forming steps in a cascade manner is highly desirable. Herein, we have developed an HFIP-alone promoted aminomethylation and intramolecular cyclization of allenamides, providing biologically relevant tetrahydro-β-carboline derivatives embedded with an allylic amine functionality. The metal-free protocol provided the desired tetrahydro-β-carboline derivatives under mild conditions. The potential of the protocol is further highlighted by the gram-scale reaction and synthesizing derivatives of biologically important molecules.

Asymmetric three-component reaction of diazo compound with alcohol and seven-membered imine

A dirhodium and chiral phosphoric acid co-catalyzed asymmetric three-component reaction of diazo compound with alcohol and seven-membered imine has been developed via Mannich-type interception of transient oxonium ylide. This reaction...

Enantioselective decarboxylative Mannich reaction of β-keto acids with C-alkynyl N-Boc N,O-acetals: access to chiral β-keto propargylamines

The chiral keto-substituted propargylamines are an essential class of multifunctional compounds in the field of organic and pharmaceutical synthesis and have attracted considerable attention, but the related synthetic approaches remain limited. Therefore, a concise and efficient method for the enantioselective synthesis of β-keto propargylamines via chiral phosphoric acid-catalyzed asymmetric Mannich reaction between β-keto acids and C-alkynyl N-Boc N,O-acetals as easily available C-alkynyl imine precursors has been demonstrated here, affording a broad scope of β-keto N-Boc-propargylamines in high yields (up to 97%) with generally high enantioselectivities (up to 97 : 3 er).

Enantioselective assembly of 3,3-disubstituted succinimides via three-component reaction of vinyl diazosuccinimides with alcohols and imines

An enantioselective three-component reaction of vinyl diazosuccinimdes with alcohols and imines has been realized by a cooperative catalysis of Rh2(OAc)4 and a chiral phosphoric acid, leading to chiral 3,3-disubstituted succinimides in good to high yields with high to excellent enantioselectivity. The generated product with an alkenyl species could be converted to the chiral tricyclic structure under mild conditions.

A Combined Computational and Experimental Study of Rh-Catalyzed C-H Silylation with Silacyclobutanes: Insights Leading to a More Efficient Catalyst System

The study of new C-H silylation reagents and reactions remains an important topic. We reported that under Rh catalysis, silacyclobutanes (SCBs) for the first time were able to react with C(sp²)-H and C(sp³)-H bonds, however the underlying reasons for such a new reactivity were not understood. Through this combined computational and experimental study on C-H silylation with SCBs, we not only depict a reaction pathway that fully accounts for the reactivity and all the experimental findings but also streamline a more efficient catalyst that significantly improves the reaction rates and yields. Our key findings include: (1) the active catalytic species is a [Rh]-H as opposed to the previously proposed [Rh]-Cl; (2) the [Rh]-H is generated via a reductive elimination/β-hydride (β-H) elimination sequence, as opposed to previously proposed endocyclic β-H elimination; (3) the regio- and enantio-determining steps are identified; (4) and of the same importance, the discretely synthesized [Rh]-H is shown to be a more efficient catalyst. This work suggests that the [Rh]-H/diphosphine system should find further applications in C-H silylations involving SCBs.

Recent advances in organocatalytic asymmetric multicomponent cascade reactions for enantioselective synthesis of spirooxindoles

Catalytic asymmetric MCCRs for enantioselective synthesis of spirooxindoles by using chiral phosphoric acids, amines, bifunctional thiourea/squaramides and metal-based reagents as catalysts.

Enantioselective synthesis of chiral α-alkynylated thiazolidones by tandem S-addition/acetalization of alkynyl imines

A SPINOL-derived chiral phosphoric acid catalyzed asymmetric formal [2 + 3]-annulation of in situ generated alkynyl imines and 1,4-dithiane-2,5-diol has been developed to afford enantiopure α-alkynylated thiazolidones with up to 72% yield and 98.5 : 1.5 er. This tandem annulation involved a tandem S-addition of alkynyl imines/intramolecular acetalization, followed by PDC-mediated oxidation. The α-alkynylated thiazolidones could facilely afford the corresponding chiral α-alkynylated or α-alkenylated cyclic sulfoxides via further elaboration.

Catalytic Asymmetric [4 + 2] Cycloaddition of ortho-Alkenyl Naphthols/Phenols with ortho-Quinone Methides: Highly Stereoselective Synthesis of Chiral 2,3,4-Trisubstituted Chromans

Chiral phosphoric acid-catalyzed biomimetic asymmetric [4 + 2] cycloaddition of ortho-alkenyl naphthols/phenols and ortho-quinone methides (o-QMs) has been demonstrated to afford various important 2,3,4-trisubstituted chromans in high yields with excellent enantio- and diastereoselectivities (up to 99% yield, 99% ee, >20:1 dr). Notably, this methodology not only enabled access to the trans-cis chiral trisubstituted chromans from 1-alkenyl 2-naphthols but also is compatible with 2-alkenyl 1-naphthols and phenols to deliver trans-trans chiral trisubstituted chromans.

Direct asymmetric N-propargylation of indoles and carbazoles catalyzed by lithium SPINOL phosphate

Catalytic asymmetric functionalization of the N–H groups of indoles and carbazoles constitutes an important but less developed class of reactions. Herein, we describe a propargylation protocol involving the use of a lithium SPINOL phosphate as the chiral catalyst and our recently developed C-alkynyl N,O-acetals as propargylating reagents. The direct asymmetric N-propargylation of indoles and carbazoles provides hitherto inaccessible N-functionalized products. Notably, the efficiency of the system allows reactions to be run at a very low catalyst loading (as low as 0.1 mol%). Mechanistic information about the titled reaction is also disclosed. This study represents an advance in the direct asymmetric functionalization of the N–H bonds of indoles and carbazoles, and additionally expands on the application of chiral alkali metal salts of chiral phosphoric acids in asymmetric catalysis.

Asymmetric functionalization of N–H bonds constitutes an important but less developed class of reactions. Here, the authors report the asymmetric direct N-propargylation of indoles and carbazoles with a lithium SPINOL phosphate as the chiral catalyst and shed light on the reaction mechanism.

A gold(i)-catalysed chemoselective three-component reaction between phenols, α-diazocarbonyl compounds and allenamides

A gold(i)-catalysed highly chemoselective three-component reaction of phenols, α-diazocarbonyl compounds and allenamides is presented. This transformation features mild reaction conditions, high functional group tolerance, and broad applicability.

Asymmetric N-aminoalkylation of 3-substituted indoles by N-protected N,O-acetals: an access to chiral propargyl aminals

A direct enantioselective N1 aminoalkylation of 3-substituted indoles is efficiently catalyzed by a phosphoric acid catalyst under mild conditions, which could be applied to the modification of tryptophan containing oligopeptides.

Catalytic Asymmetric and Divergent Synthesis of Tricyclic and Tetracyclic Spirooxindoles: Controllable Site-Selective Electrophilic Halocyclization of 1,6-Enynes

Catalytic asymmetric and divergent assembly of tricyclic and tetracyclic 3,3'-pyrrolidonyl spirooxindoles was developed, involving a one-pot chiral Brønsted base catalyzed asymmetric propargylation for the synthesis of oxindole 1,6-enynes and a subsequent switchable site-selective and highly diastereoselective electrophilic iodocyclization of 1,6-enynes. In addition, antitumor properties of the newly synthesized compounds were evaluated.