Palladacyclic N-heterocyclic carbene precatalysts for transition metal catalysis

Palladacycles remain a challenging and significant research field in organic chemistry and have emerged as a type of powerful and versatile precatalysts or key active intermediates for transition metal catalysis.These achievements in this area are correlated to the design and development of useful ancillary ligands,such as N-heterocyclic carbenes(NHCs),which not only stabilize the actual catalytic active species facilitating the transformations,but also provide additional control over the selectivity of reactions.In this context,NHCs-ligated palladacycles(NHCP_(dcycles))with different electronic and steric properties have been synthesized and applied as green precatalysts(high stability and activity,low catalyst loading and mild reaction conditions)to accelerate transition metalcatalyzed reactions.Therefore,this review focuses mainly on the strategy of NHC-Pd_(cycles) design and catalytic results obtained from representative transition metal catalysis,such as Suzuki-Miyaura,Heck-Mizoroki and Sonogashira cross-coupling reactions,Buchwald-Hartwig amination,carbonylation as well as arylation.At last,the current limitations and potential trends for further development of NHC-Pdcycles are also highlighted.

A review of enantioselective dual transition metal/photoredox catalysis

Transition metal catalysis is one of the most important tools to construct carbon-carbon and carbon-heteroatom bonds in modern organic synthesis. Visible-light photoredox catalysis has recently drawn considerable attention of the scientific community owing to its unique activation modes and significance for the green synthesis. The merger of photoredox catalysis with transition metal catalysts, termed metallaphotoredox catalysis, has become a popular strategy for expanding the synthetic utility of visiblelight photocatalysis. This strategy has led to the discovery of novel asymmetric transformations, which are unfeasible or not easily accessible by a single catalytic system. This contemporary area of organic chemistry holds promise for the development of economical and environmentally friendly methods for the asymmetric synthesis of chiral compounds. In this review, the advances in the enantioselective metallaphotoredox catalysis(EMPC) are summarized.

Transition Metal Catalyzed Enantioselective Borylative Cyclization Reactions

Due to the significance of corresponding products,enantioselective borylative cyclization reactions have been studied intensively in recent years.Many groups have developed efficient methods to transform unsaturated system into asymmetric cyclic organoboron compounds with the ring-size range from three-membered to six-membered in general.Notably,in some cases,fused rings which contain more than two contiguous chiral centers could be obtained by this kind of strategies.This review summarized and reviewed the recent advances in this field and classified these work according to the species of metal catalysts.

Transition metal-catalyzed conversion of aldehydes to ketones

Ketones are one of the most important classes of organic compounds, and widely present in various pharmacological compounds, biologically active molecules and functional materials. Over the past few decades, transition metal-catalyzed conversion of aldehydes has been found to be a powerful method.With the continuous development in recent years, it has become an efficient and uncomplicated strategy for constructing ketones. There are four major mechanisms for transition metal-catalyzed ketone synthesis from aldehyde:(1) carbonyl-Heck reaction, that is 1,2-insertion of organometal species to aldehydic C=O double bond,(2) direct insertion of transition metal catalysts to aldehydic C-H bond,(3) aldehyde as acyl radical,(4) aldehyde as carbon radical acceptor. This article summarizes related reports on the transformations of aldehydes to generate corresponding ketones under different reaction conditions.

Recent catalytic syntheses of trifluoromethylthio-containing organic compounds by transition metals,chiral organocatalysts,and photocatalysts

This review summarizes the recent advances in the catalytic syntheses of CFS-containing organic molecules using various nucleophilic or electrophilic trifluoromethylthiolating reagents.C-halogen and C—H bonds in various molecules have been transformed to C—SCFbonds by transition-metal-catalyzed reactions,such as cross-coupling of aryl halides.Enantioselective reactions controlled by chiral metal complexes or chiral organocatalysts have afforded many trifluoromethylthiolated chiral architectures,such as β-ketoesters and oxindoles.Very recently,visible-light-induced photoredox trifluoromethylthiolations have been developed,providing versatile CFS-containing structures efficiently.

Valorization of carbon dioxide with alcohols

Utilizing CO_(2)for the production of bulky and valuable chemicals presents an attractive solution to address environmental and fossil energy crises.Among the various approaches,direct carboxylation of alcohols with CO_(2)stands out as an eco-friendly process capable of efficiently producing carboxylic acids in a sustainable manner.However,the high dissociation energy of the C–O bond poses a significant challenge in this process.Over the past few decades,several strategies have been developed to activate alcohols and establish efficient catalytic systems for carboxylation with CO_(2).Nevertheless,the sporadic nature of reported approaches makes it difficult to determine the most effective one.This perspective aims to provide an overview of the current state-of-the-art catalytic protocols for carboxylating alcohols with CO_(2),encompassing esterification,halogenation,and photocatalysis,while considering their respective advantages and limitations.We aim to discern the most promising avenues for future development in this field.The insights presented in this perspective will contribute to the advancement of efficient and sustainable carboxylation methods using CO_(2),leading to the production of valuable chemicals in future.

Elucidating ligand effects in rhodium(Ⅲ)-catalyzed arene-alkene coupling reactions

Rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes are among the most powerful methods for C-C bond formation.For these transformations,subtle manipulation of ancillary ligands can lead to dramatic changes in reactivity and selectivity.However,detailed mechanistic studies concerning the ligand effects are rare.In this study,we investigated the origin of ligand-controlled product-selectivity in rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes,using a series of well-defined[CpXRhⅢ]complexes that feature electronically or sterically distinct Cp^(X)(Cp(η^(5)-C_(5)H_(5)),Cp^(CF3)(η^(5)-C_(5)Me_(4)CF_(3))and Cp^(∗)(η^(5)-C_(5)Me_(5)))ligands.A combination of experimental and theoretical investigations showed that(i)rhodium hydride species containing the electron rich Cp^(∗)ligand can undergo reinsertion of the alkene,thereby allowing rhodium-walking,(ii)rhodium hydride species involving the electron-deficient Cp or Cp^(CF3) ligands prefer reductive elimination rather than alkene insertion.These findings offer valuable insights on future rational catalyst design for selective arene-alkene cross coupling reactions.

Trisubstituted alkenes featuring aryl groups:stereoselective synthetic strategies and applications

In recent years,the synthesis and application of alkenes have attracted increased attention.Triphenylethenes(TriPEs)have lower molecular torsion than tetraphenylethenes(TPEs),which helps to balance the degree of conjugation and the aggregation-induced emission(AIE)effect.The geometry of double bonds has a significant impact on luminescence.Therefore,it is essential to provide a comprehensive summary of the stereoselective synthetic strategies for trisubstituted alkenes.In this review,common strategies for the stereoselective synthesis of alkenes are described,with an emphasis on the origin of stereoselectivity and the types of substrates.In addition,the AIE properties of TriPE and its applications in optoelectronic devices,stimuli-responsive materials,sensors,and therapies were discussed.

Recent trends and developments in the asymmetric synthesis of profens

The profens belong to a class of nonsteroidal anti-inflammatory drugs(NSAIDs),which exert significant antiinflammatory,analgesic,antipyretic and other pharmacological effects.A considerable number of catalytic asymmetric strategies for the synthesis of enantioenriched profens have been introduced.Herein are outlined recent trends and developments of promising catalytic enantioselective systems for the generation of profens and their derivatives.According to the reaction type,we divided these transformations into three categories:Transition metal-catalyzed asymmetric hydrogenations,transition metal-catalyzed asymmetric cross-couplings and organocatalytic asymmetric transformations.Overviews of generic reaction mechanisms are presented.Ideally,this tutorial review will motivate further interest in the catalytic asymmetric synthesis of highly enantioenriched profens.

Milestones in Molecular Dynamics Simulations of Single-Walled Carbon Nanotube Formation: A Brief Critical Review

We present a brief review of the most important efforts aimed at simulating single-walled carbon nanotube(SWNT)nucleation and growth processes using molecular dynamics(MD)techniques reported in the literature.MD simulations allow the spatio-temporal movement of atoms during nonequilibrium growth to be followed.Thus,it is hoped that a successful MD simulation of the entire SWNT formation process will assist in the design of chirality-specic SWNT synthesis techniques.We give special consideration to the role of the metal catalyst particles assumed in standard theories of SWNT formation,and describe the actual metal behavior observed in the reported MD simulations,including our own recent quantum chemical MD simulations.It is concluded that the use of a quantum potential is essential for a qualitatively correct description of the catalytic behavior of the metal cluster,and that carbide formation does not seem to be a necessary requirement for nucleation and growth of SWNTs according to our most recent quantum chemical MD simulations.

Recent advances in the applications of[1.1.1]propellane in organic synthesis

As a highly strained small molecule,[1.1.1]propellane has been widely used in various synthetic transformations owing to the exceptional reactivity of the central bond between the two bridgehead carbons.Utilizing strain-release approaches,the rapid development of strategies for the construction of bicyclo[1.1.1]pentane(BCP)and cyclobutane derivatives using[1.1.1]propellane as the starting material has been witnessed in the past few years.In this review,we highlight the most recent advances in this field.Accordingly,the reactivity of[1.1.1]p ropellane can be divided into three pathways,including radical,anionic and transition metal-catalyzed pathways under appropriate conditions.

Narasaka reaction:Desilylative acylation of 1-alkenylsilanes with acid anhydrides

Recent advances in the desilylative acylation of 1-alkenylsilanes with acid anhydrides under transition metal catalysis are summarized.This catalytic desilylative acylation of 1-alkenylsilanes provides an efficient route toα,β-unsaturated ketones by using rhodium or iridium as the catalyst.Moreover,various one pot sequence reactions have been developed,which can synthesizeα,β-unsaturated ketones from simple starting materials in an economic way.Additionally,this approach is applied to the asymmetric synthesis of atropisomers possessing silanol groups with excellent enantioselectivity.

Palladium-catalyzed Cycloaromatization Polymerization of Enediynes

Bergman cyclization has shown great promise in constructing conjugated polymers. However, the application of this reaction in polymer science is still limited due to the harsh reaction condition and ill-defined structure of the achieved polymers. To this end, the cycloaromatization polymerization of enediynes catalyzed by a series of transition metal catalysts is investigated in this work, by taking advantage of the coordination chemistry of the enediyne with the transition metal complexes. According to the nuclear magnetic resonance（NMR）, Fourier transform infrared（FTIR）, ultraviolet-visble（UV-Vis） spectroscopies and matrix-assisted laser desorption/ionization time-offlight mass spectrometry（MALDI-TOF MS） analysis, the cycloaromatization polymerization of enediynes proceeds under milder conditions and in a more controlled manner in the presence of palladium（II） complexes, giving structurally regulated conjugated polymers in high yields.

Highly efficient and magnetically separable nano-CuFe_2O_4 catalyzed S-arylation of thiourea by aryl/heteroaryl halides

The non-toxic and magnetically separable nano-CuFeOcatalyzed synthesis of symmetrical aryl sulfides by the reaction of thiourea with a wide variety of aryl halides,including aryl chlorides has been reported.Excellent yields of products have been obtained under ligand-free conditions and without the use of any expensive catalyst,such as palladium.

Research Progress in Enantioselective Radical Desymmetrization Reactions

Enantioselective radical desymmetrization is a highly effective approach for rapidly creating enantioenriched molecules,introducing dramatically increased structural complexity from readily available prochiral or meso compound feedstocks.Two strategic modes have been developed for these reactions,which differ in the nature of the stereo-determining steps.The first category deals primarily with the stereoselective desymmetrization of closed-shell radical precursors or functional reagents,whereas the second category achieves desymmetrization by stereoselectively functionalizing open-shell radical species.This mini-review explores the research progress in this growing field,aiming to elucidate mechanistic scenarios related to stereochemical control.Additionally,it offers insights into the challenges and opportunities that lie ahead for further development.