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.

Carbene-Catalyzed Asymmetric Ring-Opening Reaction of Biaryl Lactams to Access Axially Chiral Biaryls

Axially chiral biaryls represent the most important class of atropisomers,and they widely exist in natural products and biologically active molecules.They also constitute a unique scaffold for chiral ligands and catalysts in organic synthesis.The development of synthetic methods to obtain such chiral compounds has received widespread attention,among which catalytically atroposelective ring-opening of configurationally labile compounds represents one of the most attractive strategies.Various substrates with strained cyclic structures,such as the renowned Bringmann's lactones,can undergo asymmetric transformation into stable atropisomers.Known advancement primarily relies on metal catalyst combined with well-designed chiral ligands,the approaches utilizing organocatalysis as a critical resolution strategy are notably scarce.In this study,we disclosed a N-heterocyclic carbene(NHC)-catalyzed asymmetric ring-opening reaction of biaryl lactams via direct atroposelective nucleophilic activation.The optimized bulky carbene catalyst ensures that the reaction can proceed under mild conditions,affording the desired product with good to excellent yields and atroposelectivity.

An unprecedented synthesis of axially chiral biaryls by rearrangement and aromatization of carbocations with central-to-axial conversion of chirality

The central-to-axial chirality conversion represents a fascinating class of chemical processes consisting of the destruction of stereogenic centers and the simultaneous installation of axial chiral elements,which provides efficient methods for the preparation of axially chiral compounds.However,developing catalytic asymmetric approaches for constructing these central chirality precursors and the efficient central-to-axial chirality conversion remains a challenge due to the requirement of aromatization or elimination process.In this work,we have developed an unprecedented enantioselective intramolecular FriedelCrafts alkylation with unactivated-ketone carbonyls from which a chiral tertiary alcohol was generated with high efficiency and excellent enantioselectivity.In addition,the central-to-axial chirality conversion strategy has been successfully applied to the synthesis of enantioenriched biaryls via a less-explored carbocation-initiated rearrangement and aromatization under the promotion of Lewis acid.This methodology provided a straightforward and sustainable access to a broad range of biaryl-2-carboxylic acid and in excellent yields(up to 92%)and excellent central-to-axial chirality conversion(up to 99%conversion percentage).This work could be a great model for developing new methods for synthesizing axially chiral biaryls and a general protocol for the rearrangement and aromatization of carbocations for further functionalization.

Multicolor circularly polarized phosphorescence of axially chiral binuclear platinum(Ⅱ) complexes

D-A charge transfer, including through-bond charge transfer and through-space charge transfer between two different electron donors(D) and electron acceptors(A), is a fundamental and powerful tool to tune the optical properties of organic dyes. Herein,we demonstrate a unique strategy to tune phosphorescence and circularly polarized luminescence properties of axially chiral binuclear Pt(Ⅱ) complexes through long-range charge transfer, even though these molecules have two totally identical segments on either side of the chiral core. The presence of axial chirality would break not only the symmetry of molecular structure and π-conjugation system but also the symmetry of charge distribution for long-range charge transfer. These binaphthyl-based Pt(Ⅱ)complexes bearing coordinated atoms far away from chiral axis exhibit no Pt-Pt interactions but colorful concentrationdependent phosphorescence with quantum yield up to 86.4% and could be applied as emitters in highly efficient solutionprocessed organic light-emitting diodes to achieve luminance, luminance efficiency, power efficiency, external quantum efficiency, and asymmetry factor up to 8.94 × 10^(3)cd m^(-2), 41.9 cd A-1, 18.8 lm W^(-1), 12.6% and 2.98 × 10^(-3), respectively. Therefore,the present work affords a new and simple way to utilize the inherently asymmetric advantage of chirality for the design of D-Abased organic dyes.

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.

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.

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.

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.

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.

Organocatalytic dynamic kinetic resolution of N-arylindole lactams:atroposelective construction of axially chiral amino acids bearing a C–N chiral axis

Organocatalytic dynamic kinetic resolution of configurationally labile cyclic molecules represents one of the most efficient methods for the atroposelective construction of axially chiral molecules bearing a tetra-ortho-substituted chiral axis.Notably,this privileged strategy is limited to constructing a C–C chiral axis.Herein,organocatalytic dynamic kinetic resolution of configurationally labile N-arylindole lactams has been successfully achieved at the first time,allowing for access to a structurally diverse set of axially chiral N-arylindole amino esters with a tetra-ortho-substituted C–N chiral axis in excellent yields and atroposelectivities.In addition to the N-arylindole skeleton,N-aryl thieno[3,2-b]pyrrole,furo[3,2-b]pyrrole,and pyrrolo[2,3-b]pyridine skeletons are also compatible with this transformation.This transition-metal-free facile strategy features a broad substrate scope,mild reaction conditions,easy scale-up and excellent atom economy.Several potentially valuable molecules,such as axially chiral peptides,were efficiently generated from the resulting configurationally stable axially-chiral N-arylindole amino esters,demonstrating the power of this strategy.

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.

Scalable Cu(Ⅱ)-mediated intramolecular dehydrogenative phenol-phenol coupling:Concise synthesis of enantiopure axially chiral homo-and hetero-diphenols

An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol as the chiral auxiliary.The commercially available(R)-α-met hylbenzy la mine was identified as the best amine ligand for Cu(Ⅱ) in the reactions.A variety of homo/hetero bis-dihydroxylbenzoate substrates were examined,affording the corresponding axially chiral diphenols with satis factory to excellent diastereomeric ratios,and a representative scalable preparation was also attempted.A formal synthesis of natural product(+)-deoxyschizandrin has been achieved in this work using one axially chiral diphenol as the synthetic intermediate.

Merging C–H and C–C Activation in Pd(Ⅱ)-Catalyzed Enantioselective Synthesis of Axially Chiral Biaryls

The merging of C-H and C-C bond cleavage into one single chemical process remains a daunting challenge,especially in an asymmetric manner.Herein,a Pd(Ⅱ)-catalyzed enantioselective tandem C-H/C-C activation for the synthesis of axially chiral biaryls is described.Two types of simple cyclopropanes,such as vinylcyclopropanes and cyclopropanols,were used as efficient and readily available coupling partners.

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.

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.

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.

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.

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.

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.

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].