Catalytic Domino Research Articles

Electrochemical Enantioselective C-H Annulation by Achiral Rhodium(III)/Chiral Brønsted Base Domino Catalysis.

Rhodium(III)-catalyzed enantioselective C-H activation has emerged as a powerful tool for assembling enabling chiral molecules. However, this approach is significantly hampered by the cumbersome synthetic routes for preparing chiral rhodium catalysts. In sharp contrast, we herein report on an electrochemical domino catalysis system that exploits an achiral Cp*-rhodium catalyst along with an easily accessible chiral Brønsted base for an enantioselective C-H activation/annulation reaction of alkenes by benzoic acids. Our strategy offers an environmentally benign and most user-friendly approach for assembling synthetically useful chiral phthalides in good enantioselectivity, employing electricity as the sustainable oxidant.

Molybdenum‐Catalyzed One‐Pot Multi‐Step Synthesis of N‐Polyheterocycles from Nitroarenes and Glycols

We report the efficient, sustainable one‐pot synthesis of a wide variety of N‐polyheterocycles, such as imidazo‐quinolines and quinoxalines, and furoquinolines, from easily available nitroaromatics and glycols via a molybdenum catalytic domino reduction‐imine formation‐intramolecular cyclization‐oxidation sequence. It is worth highlighting that the recycling and incorporation of the waste carbonyl byproduct, generated in the reduction step, into the final compound is realized. In addition, the overall efficiency and atom economy of the process are further improved owing to the participation of one reaction intermediate as reductant that allows lowering the amount of external reducing agent employed.

Enantioselective Synthesis of Indole‐Derivated Axially Chiral Frameworks via CpXRh(III)‐Catalyzed Domino Cyclization/C3‐Arylation of 2‐Alkynylanilines with 1‐Diazonaphthoquinones

AbstractWe report herein a chiral CpXRh(III)‐catalyzed domino cyclization/C3‐arylation process using 2‐alkynylanilines and 1‐diazonaphthoquinones as viable substrates, delivering indole‐based derivatives endowed with axial chirality. The method features high enantioselectivity, broad substrate scope, and robust functional group tolerance. Subsequent functionalization of the synthesized scaffolds underlines the practicality of this approach in the design of indole‐derivated axially chiral frameworks, demonstrating its substantial promise in synthetic and medicinal chemistry applications.

Organocatalyst-mediated asymmetric one-pot/two domino/three-component coupling reactions for the synthesis of trans-hydrindanes.

Highly substituted trans-hydrindanes were synthesized by the three-component coupling reactions of 1,3-diethyl 2-(2-oxopropylidene)propanedioate and two different α,β-unsaturated aldehydes catalyzed by diphenylprolinol silyl ether. The reaction proceeds via two successive independent catalytic domino reactions in a one-pot reaction by a single chiral catalyst. Domino reactions involve Michael/Michael and Michael/aldol reactions to afford trans-hydrindanes with excellent diastereoselectivity and nearly optically pure form.

Catalytic Domino Three-Component Synthesis of Functionalized Heterocycles from Carbon Dioxide.

A catalytic domino, three-component reaction has been developed for the transformation of carbon dioxide into functionalized six-membered cyclic carbonates. The catalytic process combines an initial carboxylative cyclization of β-epoxy alcohols followed by an oxa-Michael reaction affording an unparalleled scope of heterocyclic structures. The wide range of functional groups, including free-alcohols, empowers the access to a range of products including C11-oxo-based bicyclic heterocycles. The versatility of these functionalized carbonates is further complemented by a series of synthetic diversifications. Control experiments are consistent with the first step of this domino process being promoted by a binary Lewis acid/base catalyst, while the second stage only requires catalytic base.

Rapid Assembly of Unsymmetrically Linked Bis-heterocycles via Palladium Domino Catalysis.

A palladium-catalyzed domino reaction of alkene-tethered oxime esters is reported. This transformation uses an air-stable palladium precatalyst that initiates a Narasaka-Heck reaction, that is interrupted with a Pd(II)-promoted cyclization. Through this methodology, a novel class of unsymmetrical alkyl-linked bis-heterocycles were synthesized in yields up to 99%. The reaction is scalable up to 1.0 mmol, with simplified purification steps. This transformation expands the scope of accessible bis-heterocycles available through Narasaka-Heck reactions beyond C-H activation and direct anionic capture termination steps.

Domino catalysis for selective dehydrogenation of ethane with shifted thermodynamic equilibrium

Domino catalysis for selective dehydrogenation of ethane with shifted thermodynamic equilibrium

Silver‐Mediated Cascade Synthesis of Functionalized 1,4‐Dihydro‐2H‐benzo‐1,3‐oxazin‐2‐ones from Carbon Dioxide

AbstractA conceptually novel catalytic domino approach is presented for the synthesis of highly functional 1,4‐dihydro‐2H‐1,3‐benzoxazine‐2‐one derivatives. Key to the chemoselectivity is a proper design of the precursor to override thermodynamically favored parasitic cyclization processes and empower the formation of the desired product through Thorpe–Ingold effects. The synthetic diversity of these CO2‐based heterocycles is further demonstrated, and the isolation of a reaction intermediate supports an unusual ring‐expansion sequence from an α‐alkylidene, five‐membered cyclic carbonate to a six‐membered cyclic carbamate by N‐induced isomerization.

Silver-Mediated Cascade Synthesis of Functionalized 1,4-Dihydro-2H-benzo-1,3-oxazin-2-ones from Carbon Dioxide.

A conceptually novel catalytic domino approach is presented for the synthesis of highly functional 1,4-dihydro-2H-1,3-benzoxazine-2-one derivatives. Key to the chemoselectivity is a proper design of the precursor to override thermodynamically favored parasitic cyclization processes and empower the formation of the desired product through Thorpe-Ingold effects. The synthetic diversity of these CO2 -based heterocycles is further demonstrated, and the isolation of a reaction intermediate supports an unusual ring-expansion sequence from an α-alkylidene, five-membered cyclic carbonate to a six-membered cyclic carbamate by N-induced isomerization.

Catalytic enantioselective alkenylation-heteroarylation of olefins: stereoselective syntheses of 5-7 membered azacycles and oxacycles.

Catalytic enantioselective domino alkenylation-heteroarylation of nonconjugated iododienes proceeded with excellent stereoselectivity and broad scope of substrates. The reaction enables stereoselective syntheses of substituted azacycles such as piperidine, pyrrolidine azepine and dihydropyrans carrying new quaternary stereocenters. Mechanistically, C-H bonds of heterocycles were activated by lithium alkoxides via reversible deprotonation, rather than conventional palladium(ii)-assisted metalation processes. Many types of heteroarenes can be used, including not only azoles (such as thiazoles, oxazoles, imidazoles and oxadiazoles), but also nonazoles (thiophene, furan and azine N-oxides).

Metalloporphyrins as Catalytic Models for Studying Hydrogen and Oxygen Evolution and Oxygen Reduction Reactions.

The hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are involved in biological and artificial energy conversions. H-H and O-O bond formation/cleavage are essential steps in these reactions. In nature, intermediates involved in the H-H and O-O bond formation/cleavage are highly reactive and short-lived, making their identification and investigation difficult. In artificial catalysis, the realization of these reactions at considerable rates and close to their thermodynamic reaction equilibria remains a challenge. Therefore, the elucidation of the reaction mechanisms and structure-function relationships is of fundamental significance to understand these reactions and to develop catalysts.This Account describes our recent investigations on catalytic HER, OER, and ORR with metalloporphyrins and derivatives. Metalloporphyrins are used in nature for light harvesting, energy conversion, electron transfer, O2 activation, and peroxide degradation. Synthetic metal porphyrin complexes are shown to be active for these reactions. We focused on exploring metalloporphyrins to study reaction mechanisms and structure-function relationships because they have stable and tunable structures and characteristic spectroscopic properties.For HER, we identified three H-H bond formation mechanisms and established the correlation between these processes and metal hydride electronic structures. Importantly, we provided direct experimental evidence for the bimetallic homolytic H-H bond formation mechanism by using sterically bulky porphyrins. Homolytic HER has been long proposed but rarely verified because the coupling of active hydride intermediates occurs spontaneously and quickly, making their detection challenging. By blocking the bimolecular mechanism through steric effects, we stabilized and characterized the NiIII-H intermediate and verified homolytic HER by comparing the reaction behaviors of Ni porphyrins with and without steric effects. We therefore provided an unprecedented example to control homolytic versus heterolytic HER mechanisms through tuning steric effects of molecular catalysts.For the OER, the water nucleophilic attack (WNA) on high-valent terminal Mn-oxo has been proposed for the O-O bond formation in natural and artificial water oxidation. By using Mn tris(pentafluorophenyl)corrole, we identified MnV(O) and MnIV-peroxo intermediates in chemical and electrochemical OER and provided direct experimental evidence for the Mn-based WNA mechanism. Moreover, we demonstrated several catalyst design strategies to enhance the WNA rate, including the pioneering use of protective axial ligands. By studying Cu porphyrins, we proposed a bimolecular coupling mechanism between two metal-hydroxide radicals to form O-O bonds. Note that late-transition metals do not likely form terminal metal-oxo/oxyl.For the ORR, we presented several strategies to improve activity and selectivity, including providing rapid electron transfer, using electron-donating axial ligands, introducing hydrogen-bonding interactions, constructing dinuclear cooperation, and employing porphyrin-support domino catalysis. Importantly, we used Co porphyrin atropisomers to realize both two-electron and four-electron ORR, representing an unparalleled example to control ORR selectivity by tuning only steric effects without modifying molecular and/or electronic structures.Lastly, we developed several strategies to graft metalloporphyrins on various electrode materials through different covalent bonds. The molecular-engineered materials exhibit boosted electrocatalytic performance, highlighting promising applications of molecular electrocatalysis. Taken together, this Account demonstrates the benefits of exploring metalloporphyrins for the HER, OER, and ORR. The knowledge learned herein is valuable for the development of porphyrin-based catalysts and also other molecular and material catalysts for small molecule activation reactions.

Mo-Catalyzed One-Pot Synthesis of N-Polyheterocycles from Nitroarenes and Glycols with Recycling of the Waste Reduction Byproduct. Substituent-Tuned Photophysical Properties.

A catalytic domino reduction–imine formation–intramolecular cyclization–oxidation for the general synthesis of a wide variety of biologically relevant N‐polyheterocycles, such as quinoxaline‐ and quinoline‐fused derivatives, and phenanthridines, is reported. A simple, easily available, and environmentally friendly dioxomolybdenum(VI) complex has proven to be a highly efficient and versatile catalyst for transforming a broad range of starting nitroarenes involving several redox processes. Not only is this a sustainable, step‐economical as well as air‐ and moisture‐tolerant method, but also it is worth highlighting that the waste byproduct generated in the first step of the sequence is recycled and incorporated in the final target molecule, improving the overall synthetic efficiency. Moreover, selected indoloquinoxalines have been photophysically characterized in cyclohexane and toluene with exceptional fluorescence quantum yields above 0.7 for the alkyl derivatives.

Editorial: The Catalysis of Ring Synthesis

Ring synthesis via catalysis has emerged as a transformative platform. This Special Collection of articles on “The Catalysis of Ring Synthesis” covers the most recent strategies of ring syntheses, including catalytic domino reactions and one-pot processes, and presents the current progress in this exciting field. The contributions include transition-metal catalysis, organocatalysis, nanocatalysis, photoredox catalysis towards preparing carbocyclic and heterocyclic compounds of potential interest for life and material sciences.

Cu‐Catalyzed Selective Synthesis of Propargylamines via A3‐Coupling/Aza‐Michael Addition Sequence: Amine Loading Controls the Selectivity

AbstractPropargylamines are valuable molecules in medicinal chemistry and organic synthesis. A3 reaction is straightforward access to construct propargylamine and its derivatives. Here we report operationally simple catalytic domino A3‐coupling/aza‐Michael addition of a primary amine, formaldehyde solution, an alkyne, and an olefin using copper as a catalyst to produce a series of functionalized propargylamines in moderate to excellent yields. This protocol involves a competition between aza‐Michael addition and Mannich reaction. By changing the amount loading of amines to control the process of Mannich reaction is the key procedure of increasing the selectivity.

Catalytic three-component dicarbofunctionalization reactions involving radical capture by nickel.

The catalytic dicarbofunctionalization of unsaturated π bonds represents a powerful platform for the rapid construction of complex motifs. Despite remarkable progress, novel and efficient methods for achieving such transformations under milder conditions with chemo-, regio-, and stereoselectivity still remain a significant challenge; thus, their development is highly desirable. Recently, the merging of nickel catalysis with radical chemistry offers a new and benign platform for the catalytic dicarbofunctionalization of unsaturated π bonds with unprecedented reactivity and selectivity. In this review, we summarize the recent advances in this area by underpinning the catalytic domino transformations involving radical capture by nickel to provide a clear overview of reaction designs and mechanistic scenarios.

Kinetic Analysis of Domino Catalysis: A Case Study on Gold-Catalyzed Arylation

Domino catalysis is a well-explored route to increasing the efficiency of multistep reactions. However, the kinetic features required for efficient turnover of a process where “multiple transformat...

Catalytic Asymmetric Domino Michael/Annulation Reaction of Bifunctional Chromone Synthons with β,γ-Unsaturated α-Keto Esters: Rapid Access to Polysubstituted Spirocyclic Hexahydroxanthones

A thiourea-catalyzed asymmetric domino Michael/annulation process was devised employing bifunctional oxindole-chromones as C4 synthons and β,γ-unsaturated α-keto esters as C2 synthons. This reaction enables the highly diastereo- and enantioselective synthesis of a range of biologically relevant spirocyclic hexahydroxanthones with one quaternary and four tertiary stereogenic centers, also featuring an intriguing combination of two privileged motifs, including hexahydroxanthone and oxindole substructures, in good yields (up to 76%) and excellent stereoselectivities (up to >99% ee and >20:1 dr). Moreover, using β,γ-unsaturated α-keto esters as the C2 building blocks, which are different from enone substrates such as chalcone and benzalacetone, with the reversible Michael reaction further expanded the scope of the method. In addition, scale-up also demonstrated the applicability of this protocol.

A Catalytic Domino Approach toward Oxo-Alkyl Carbonates and Polycarbonates from CO2, Propargylic Alcohols, and (Mono- and Di-)Alcohols

We have explored the domino reaction between propargylic alcohols, carbon dioxide and various alcohols with the double objective to prepare oxo-alkylcarbonates with a high yield and selectivity und...

Synthesis of Chiral 3-Substituted 3-Amino-2-oxindoles through Enantioselective Catalytic Domino and Tandem Reactions

The goal of this review is to collect the major developments in the catalytic asymmetric synthesis of 3-substituted 3-amino-2-oxindoles through enantioselective catalytic domino and tandem reactions reported since 2011.1 Introduction2 Organocatalyzed Reactions3 Metal-Catalyzed Reactions4 Conclusion

Asymmetric Synthesis of Cyclopentene-Fused Tetrahydroquinolines via N-Heterocyclic Carbene Catalyzed Domino Reactions

A new strategy for the N-heterocyclic carbene catalyzed asymmetric synthesis of cyclopentene-fused tetrahydroquinoline derivatives has been developed. The one-pot organocatalytic domino protocol allows a direct entry to the characteristic cyclopenta[c]tetrahydroquinoline core of many alkaloids and some potential drugs employing readily available quinolinone and enal substrates in good domino yields and stereoselectivities.