C_3-Symmetric Molecules with Axial Chirality and Handed Arrangement of Dipole Fields

Introduction Chirality is defined as the absence of inversion symmetry,however,it is actually a pseudo-scalar of objects or figures,and does not depend for its definition on any connection to the physical world[1-5]. Logically,chiral molecules may possess other inherent physical quantity that guarantees the connection to the physical world[6,7].

Synthesis of C—N Axial Chirality N-Arylindoles via Pd(II)-Catalyzed Free Amine-Directed Atroposelective C—H Olefination

Axially chiral N-arylindoles bearing a stereogenic C—N axis are unique important scaffolds in natural products,advance materials,pharmaceuticals and privileged chiral ligands or catalysts.Herein,we report the direct synthesis of C—N axially chiral N-arylindoles through a Pd-catalyzed free amine-directed atroposelective C—H olefination enabled by a spiro phosphoric acid(SPA)ligand.A wide range of enantioenriched N-aromatic amine indoles were obtained in high yields with good enantioselectivities(35 examples,up to 91%yield and up to 96%ee).The chiral products with free amine group offer an effective functional handle for down-stream diversity-oriented synthesis.

Catalytic Enantioselective Simultaneous Control of Axial Chirality and Central Chirality in Allenes

Chiral molecules, which may contain one or more different type（s） of stereocentres, such as central, axial, planar, and helical chiralities, etc., are indispensable in chemistry, pharmaceutical industry, and life science. Despite many advances for the preparation of chiral molecules usually with a single type of chirality have been realized, simultaneous construction of different types of chiralities is still a significant challenge. Here, we wish to report a protocol for preparation of chiral allenes with both central and axial chiralities via a catalytic asymmetric allenylation of different biologically or syn- thetically useful fluorinated or non-fluorinated nucleophiles with readily available racemic allenes by using a single chiral ligand. An echoing between the central chirality and axial chirality for the enantioselectivity was observed. This strategy provides a general and practical approach to functionalized optically active allenes bearing both central and axial chiralities with an excellent enantioselectivity under mild conditions.

Catalytic asymmetric Catellani-type reaction: A powerful tool for axial chirality construction

This highlight summarizes a recent development of a catalytic enantioselective Catellani-type reaction for the synthesis of axially chiral biaryls.The chirality induction is solely governed by chiral norbornene ligand in the Pd mediated ortho C–H functionalization and ipso cross-coupling transformation.The preparative power of the methodology is demonstrated as a powerful manifold for the divergent synthesis of structurally diverse axially chiral biaryls and chiral fluorenols.

Rare π_5~6…Pb Interactions in a Two-dimensional Metal-organic Coordination Polymer with Two Distinct Kinds of Axially Chiral Units

A new metal-organic coordination polymer [Pb（mfpdc）（CH3OH）]n （1, mfpdc = 2,6-dimethyl-4-（2-furanyl） pyridine-3,5-dicarboxylate） was synthesized and characterized by single-crystal X-ray analyses. The crystal is orthorhombic, space group Pbca, a = 15.6297（18）, b = 9.4803（11）, c = 18.598（2） A, V= 2755.8（6） A3, Z = 8, Mr= 498.44, Dc= 2.403 Mg/m3, F（000） = 1872, the final R = 0.0275 and wR = 0.0726 （1 〉 2σ（I））. There are interesting polynuclear zigzag （PbOs）n chains in the structure of 1, and there have interesting axially chiral S- and R-unit Pb4L units constructed from prochiral organic ligands through C-H...O bonding. The （R/S）-Pb4L units by sharing Pb centers generate a 2-D coordination network, in which there exist rare n65Pb （3.2610 A） interactions. The solid-state photoluminescent emission of compound 1 appears at 487 nm.

Axial enantiomers with donor-regulated TADF feature for multicolor circularly polarized electroluminescence

This study optimized the TADF feature of axial chiral enantiomers through precise donor engineering,and multicolor CP-TADFwas achieved in the axial chiral framework.Three pairs of axial enantiomers with donor-regulated TADF feature,namely(R/S)-TPCBD,(R/S)-DPCBD,and(R/S)-DPACBD,were synthesized by introducing carbazole donors with different substituents onto biphenyl cyanide acceptors.As the electron-donating ability of donors increases,the emission of these axial enantiomers ranges from 455,476 to 552 nm,their singlet-triplet energy gaps(ΔE_(ST))gradually decrease from 0.30,0.22 to 0.02 e V,accompanied by an increasement in the transition rate(k_(RISC))of RISC process,and the k_(RISC)of DPACBD could reach up to 7.16×10^(5)s^(-1).These axial enantiomers also exhibit mirror-image CD and circularly polarized luminescence(CPL)properties.Moreover,OLEDs based on TPCBD,DPCBD,and DPACBD as emitter were then fabricated,which displayed blue,green,and orange electroluminescence with EQE_(max)of 13.0%,16.4%,and 25.0%,respectively.The results also exhibited a phenomenon of device efficiency increasing with the enhancement of donor abilities.Notably,the CP-OLEDs using(R/S)-TPCBD,(R/S)-DPCBD and(R/S)-DPACBD as emitters displayed intense CPEL signals with g_(EL)values of 3.4×10^(-3)/-4.1×10^(-3),3.2×10^(-3)/-3.1×10^(-3)and2.3×10^(-3)/-2.1×10^(-3),respectively.By convenient molecular engineering of donor regulation in the same molecular skeleton,CP-TADF materials with multicolor CPEL and improved device performance could be conveniently achieved.

Recent advances in the construction of axially chiral arylpyrroles

Catalytic enantioselective preparation of axially chiral molecules has gained considerable interest over the past decades, due to their numerous applications in bioactive molecules, natural products, pharmaceuticals, materials, ligands, and catalysts. Compared with the well-established synthetic approaches for six-membered axially chiral skeletons, methodologies directed towards five-membered axially chiral compounds are relatively rare. Among these, axially chiral arylpyrroles are especially important structural motifs with wide utility, and the atroposelective synthesis of them is highly desirable. In recent years, novel strategies have been developed based on transition-metal catalysis and organocatalysis. This review summarizes the recent achievements in atroposelective preparation of arylpyrroles, by emphasizing the synthetic methods for each axially chiral framework, reaction mechanisms, and applications.

Design and synthesis of axially chiral aryl-pyrroloindoles via the strategy of organocatalytic asymmetric(2+3)cyclization

The catalytic asymmetric construction of axially chiral indole-based frameworks is an important area of research due to the unique characteristics of such frameworks.Nevertheless,research in this area is still in its infancy and has some challenges,such as designing and constructing new classes of axially chiral indole-based scaffolds and developing their applications in chiral catalysts,ligands,etc.To overcome these challenges,we present herein the design and atroposelective synthesis of aryl-pyrroloindoles as a new class of axially chiral indole-based scaffolds via the strategy of organocatalytic asymmetric(2+3)cyclization between 3-arylindoles and propargylic alcohols.More importantly,this new class of axially chiral scaffolds was derived into phosphines,which served as efficient chiral ligands in palladium-catalyzed asymmetric reactions.Moreover,theoretical calculations provided an in-depth understanding of the reaction mechanism.This work offers a new strategy for constructing axially chiral indole-based scaffolds,which are promising for finding more applications in asymmetric catalysis.

Visible Light-Mediated Cobalt and Photoredox Dual-Catalyzed Asymmetric Reductive Coupling for Axially Chiral Secondary Alcohols

Secondary alcohols bearing both axial and central chirality comprise attractive biological activity and exhibit excellent chiral induction in asymmetric reactions.However,only very limited asymmetric catalytic approaches were developed for their synthesis.We herein describe visible light-mediated cobalt-catalyzed asymmetric reductive Grignard-type addition of aryl iodides with axially prochiral biaryl dialdehydes leading to the direct construction of axially chiral secondary alcohols.Preliminary mechanistic studies indicate that efficient kinetic recognition of diastereomers might occur for axially prochiral dialdehydes to improve the stereoselectivity,which might open a new avenue for the challenging cascade construction of multiple chiral elements.This protocol features excellent enantio-and diastereoselectivity,green and mild conditions,simple operation,and broad substrate scope,providing a modular platform for the synthesis of secondary axially chiral alcohols.

Chiral Phosphoric Acid Catalyzed Asymmetric Synthesis of Axially Chiral Compounds

The well-defined conformational properties of axially chiral compounds bring extraordinary values to an assortment of bioactive molecules,advanced materials,organocatalysts as well as chiral ligands in asymmetric transformations.The demonstrated usefulness and untapped potential of axially chiral structural motifs stimulate increasing efforts to develop novel and efficient approaches for their preparation.In this regard,the chiral phosphoric acids broadly used in asymmetric Brønsted acid catalysis have shown high relevance for atroposelective synthesis as well.Our strong interest in reaction chemistry of atropisomers has established a rewarding research programme in our group.The course of studies will be recounted in this account,with discussion focused on the use of chiral phosphoric acids to catalyze construction of several key axially chiral structures such as BINAM,BINOL,NOBIN,arylquinones,SPINOL,arylpyrrole analogues and axially chiral alkenes.

Catalytic Asymmetric Synthesis of Axially Chiral 3,3'-Bisindoles by Direct Coupling of Indole Rings

Comprehensive Summary A new strategy for the enantioselective synthesis of axially chiral 3,3'-bisindoles was devised by the direct coupling of two indole rings.This strategy makes use of the C3-umpolung reactivity of 2-indolylmethanols,which enables the catalytic asymmetric addition reaction of 2-indolylmethanols with rationally designed 2-substituted indoles,thus constructing axially chiral 3,3'-bisindole scaffolds in overall excellent yields(up to 98%)with high enantioselectivities(up to 96:4 er).This approach not only has overcome the challenges in constructing axially chiral five-five-membered heterobiaryls,but also represents a new application of the C3-umpolung reactivity of 2-indolylmethanols in asymmetric catalysis.More importantly,this class of axially chiral 3,3'-bisindoles can undergo a variety of post-functionalizations to give axially chiral 3,3'-bisindole-based organocatalysts,which have found their preliminary applications in asymmetric catalysis.

Design and catalytic atroposelective synthesis of axially chiral isochromenone-indoles

The catalytic atroposelective synthesis of axially chiral isochromenone-indoles has been established by the strategy of designing homophthalic anhydride-based indole derivatives as a new type of indole-based platform molecules for dynamic kinetic resolution.By this strategy,a wide range of axially chiral isochromenone-indoles were synthesized in high yields with excellent enantioselectivities(up to 98% yield,97% ee) via the catalytic asymmetric sulfonylation reaction of homophthalic anhydridebased indole derivatives with aryl sulfonyl chlorides under the catalysis of chiral quaternary ammonium salt as a phase-transfer catalyst.

Atroposelective Construction of Axially Chiral Alkene-lndole Scaffolds via Catalytic Enantioselective Addition Reaction of 3-Alkynyl-2-indolylinethanols

Atroposelective construction of axially chiral alkene-heteroaryl scaffolds is highly desired but challenging.In this work,we established an atroposelective construction of axially chiral alkene-indole scaffolds via the strategy of catalytic enantioselective addition reaction of 3-alkynyl-2-indolylmethanols with bulky nucleophiles.

Axially Chiral Dodecanuclear Lanthanide Clusters Constructed by“Bottom-Up” Self-assembly for Enantioselective Sensing

Via the bottom-up synthetic strategy,we synthesized a pair of dodecanuclear metal clusters of Eu_(12)(C_(2)O_(4))_(9)(R/S-BNP)_(18)(EtOH)_(6)-(H_(2)0)_(6)·8EtOH-7H_(2)0(complex 2),which represent the largest axial chiral lanthanide metal clusters.In the structure,rare four-pointed star coordination mode of oxalic acid is reported by this work.In addition,as a fluorescence sensor,the complex 2 exhibits high enantioselectivity for R-/S-BINOL-TF_(2)(EF=2.87)and other chiral binaphthyl derivatives.

Atroposelective Synthesis of 2-Arylindoles via Chiral Phosphoric Acid-Catalyzed Direct Amination of Indoles

Indole-based atropisomers are a very important class of axially chiral compounds.However,the atroposelective synthesis of axially chiral 2-arylindole remains largely unexplored.In this study,we report the successful synthesis of atropisomeric 2-arylindoles using direct amination of indoles with p-quinonediimines in the presence of chiral phosphoric acid as a catalyst.Quinonediimine acts as an aminating reagent through formal polarity inversion of imine.The malonate group on the 2-aryl of 2-indoles was found to be essen-tial for high enantioselectivity of the products.This could be due to the additional interaction between the ester group and the cata-lyst,as well as the intramolecular hydrogen bonding.Our findings provide a new strategy for the asymmetric construction of 2-arylindole atropisomers.

Ion-Pairing Chirality Transfer in Atropisomeric Biaryl-Centered Gold Clusters

The stereocontrol of chiral metal clusters and nanoclusters has become a focus of interest in metal cluster chemistry due to their promising applications in asymmetric catalysis.Despite being a general chirality transfer strategy,the ion-pairing process is still ambiguous in the course of bestowing chirality to metal clusters.Here we construct a biaryl-centered axially chiral gold-cluster system to study an outside-in ion-pairing chirality transfer process.Four hexanuclear gold(I)clusters,centered by two types of biaryl ligands[(2-indolyl)aniline(L^(1))and biindole(L^(2))],were synthesized via in situ cyclization reactions.In the crystalline state,the biaryl centers showed axial chirality in which the gold atoms were in an asymmetric arrangement.In solution,the chiral phosphates induced an outside-in chirality transfer by significant interactions with the periphery of the biaryl-centered gold clusters.Finally,the chiral resolution of hexa-aurated biindoliums was accomplished via an efficient outside-in chirality transfer process relying on strong aurophilic interaction and extra peripheral coordination.This study not only deepens the understanding of the outside-in ion-pairing chirality transfer process but also provides a new approach for fabricating desired chiral metal clusters by a combination of organometallic transformation and chirality transfer.

Catalytic Atroposelective Catellani Reaction Enables Construction of Axially Chiral Biaryl Monophosphine Oxides

An unprecedented atroposelective Catellani reaction between phosphine oxide-containing aryl bromides,aryliodides,and nucleophiles for the construction of phosphine-containing biaryl atropisomers was established using an enantiopure norbornene derivative as the chiral mediator.A broad range of atropisomeric biaryl-based monophosphine oxides were obtained in good efficiency with excellent enantioselectivity.

Synthesis of axially chiral oxazoline–carbene coordinated palladium complexes with a N-phenyl framework

A family of tropos ligands bearing a N-heterocyclic carbene and a chiral oxazoline coordination group with a N-phenyl framework were easily prepared,and their coordination behavior with Pd（Ⅱ）acetate was performed,affording a series of axially chiral palladium complexes in good yields.

Construction of axially chiral compounds via catalytic asymmetric radical reaction

The chemistry of axially chiral compounds has emerged as a subject of increasing interest due to their widespread presence in natural products,bioactive molecules,advanced materials,and chiral ligands/catalysts.On the other hand,catalytic asymmetric radical-based transformations provide a complementary platform for the construction of enantiomerically enriched molecules that are in growing demand in the chemical and pharmaceutical in-dustries.In recent years,considerable research efforts have been devoted to the development of catalytic asymmetric radical reactions for the construction of axially chiral compounds based on the unique reactivity modes of diverse radicals.In this review,we critically illustrate these recent achievements according to different radical precursors and catalytic activation modes.Wherever possible,special emphasis is also placed on the discussion of mechanistic features underlying these works and substrate scopes.This review should be of great interest to the experts in this area,but also serve as a helpful starting point for new researchers in this field.

Synthesis of Axially Chiral Anilides Enabled by a Palladium/Ming-Phos-Catalyzed Desymmetric Sonogashira Reaction

Atropisomeric anilides are one of important C-N axially chiral compounds.Compared with the A/-terminal functionalization to prepare such compounds,C-terminal functionalization strategies have been rarely reported.We describe herein an efficient synthesis of axially chiral anilides enabled by Pd-catalyzed desymmetric Sonogashira cross-coupling reactions with the use of a newly identified Ming-Phos.Moderate to high yields with high enantioselectivities(up to 98%ee)were obtained.