Axially chiral indole‐based frameworks have been recognized as a class of important five‐membered heterobiaryls and developing catalytic asymmetric approaches for constructing these frameworks in an ...enantioselective manner is highly desirable. In recent years, synthetic chemists have paid much attention to this research field, and rapid developments have occurred. At this point, a range of axially chiral indole‐based scaffolds have been constructed via various catalytic asymmetric reactions based on different strategies. Thus, the catalytic asymmetric construction of axially chiral indole‐based frameworks has become an emerging area. This minireview summarizes the rapid advances in this field and gives some insights into future developments, which will help this research field to thrive.
Axially chiral indole‐based frameworks have been recognized as an important class of five‐membered heterobiaryls, and the catalytic asymmetric construction of this class of frameworks has become an emerging area. To give an in‐depth understanding of this area, this Minireview not only analyses its history and development trends, but also gives some insights into future developments based on the summarization of the rapid advances in this field.
A new class of axially chiral styrene‐based thiourea tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements, and multiple ...activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo‐, diastereo‐, and enantioselective (2+4) cyclization of 2‐benzothiazolimines with homophthalic anhydrides in good yields (up to 96 %) with excellent stereoselectivities (all >95:5 dr, up to 98 % ee). More importantly, theoretical calculations elucidated the important role of an axially chiral styrene moiety in controlling both the reactivity and enantioselectivity. This work not only represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, but also gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.
A new class of axially chiral styrene‐based organocatalysts has been rationally designed. They enable the chemo‐, diastereo‐ and enantioselective (2+4) cyclization of 2‐benzothiazolimines. This work represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, and it gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.
Conversion of carbon dioxide (CO2) into valuable chemicals, especially liquid fuels, through electrochemical reduction driven by sustainable energy sources, is a promising way to get rid of ...dependence on fossil fuels, wherein developing of highly efficient catalyst is still of paramount importance. In this study, as a proof‐of‐concept experiment, first a facile while very effective protocol is proposed to synthesize amorphous Cu NPs. Unexpectedly, superior electrochemical performances, including high catalytic activity and selectivity of CO2 reduction to liquid fuels are achieved, that is, a total Faradaic efficiency of liquid fuels can sum up to the maximum value of 59% at −1.4 V, with formic acid (HCOOH) and ethanol (C2H6O) account for 37% and 22%, respectively, as well as a desirable long‐term stability even up to 12 h. More importantly, this work opens a new avenue for improved electroreduction of CO2 based on amorphous metal catalysts.
An amorphous Cu catalyst displays superior catalytic activity toward electroreduction of CO2 with a remarkable selectivity for the reduction to liquid fuels (HCOOH andC2H6O) relative to a crystalline Cu catalyst.
The regio‐ and enantioselective (3+3) cycloaddition of nitrones with 2‐indolylmethanols was accomplished by the cooperative catalysis of hexafluoroisopropanol (HFIP) and chiral phosphoric acid (CPA). ...Using this approach, a series of indole‐fused six‐membered heterocycles were synthesized in high yields (up to 98 %), with excellent enantioselectivities (up to 96 % ee) and exclusive regiospecificity. This approach enabled not only the first organocatalytic asymmetric (3+3) cycloaddition of nitrones but also the first C3‐nucleophilic asymmetric (3+3) cycloaddition of 2‐indolylmethanols. More importantly, theoretical calculations elucidated the role of the cocatalyst HFIP in helping CPA control the reactivity and enantioselectivity of the reaction, demonstrating a new mode of cooperative catalysis.
The regio‐ and enantioselective (3+3) cycloaddition of nitrones with 2‐indolylmethanols has been established under the cooperative catalysis of hexafluoroisopropanol (HFIP) and chiral phosphoric acid (CPA). This approach not only realized the first organocatalytic asymmetric (3+3) cycloaddition of nitrones and the first C3‐nucleophilic asymmetric (3+3) cycloaddition of 2‐indolylmethanols but also revealed a new mode of cooperative catalysis.
Efficient and selective dehydrogenation of formic acid is a key challenge for a fuel‐cell‐based hydrogen economy. Though the development of heterogeneous catalysts has received much progress, their ...catalytic activity remains insufficient. Moreover, the design principle of such catalysts are still unclear. Here, experimental and theoretical studies on a series of mono‐/bi‐metallic nanoparticles supported on a NH2‐N‐rGO substrate are combined for formic acid dehydrogenation where the surface energy of a metal is taken as a relevant indicator for the adsorption ability of the catalyst for guiding catalyst design. The AuPd/NH2‐N‐rGO catalyst shows record catalytic activity by reducing the energy barrier of rate controlling steps of formate adsorption and hydrogen desorption. The obtained excellent results both in experiments and simulations could be extended to other important systems, providing a general guideline to design more efficient catalysts.
A AuPd/NH2‐N‐rGO catalyst shows supreme catalytic performance for the decomposition of formic acid at room temperature, with a turnover frequency (TOF) of 4445.6 h−1. Developments in the experiments and simulations of high‐performance catalysts may promote the practical application of formic acid as a promising hydrogen storage material.
Exosomes extracted from mesenchymal stem cells (MSCs) was reported to reduce myocardial ischemia/reperfusion damage. Besides, stromal‐derived factor 1 (SDF1a) functions as cardiac repair after ...myocardial infarction (MI). Therefore, the present study aims to identify whether exosomes (Exo) released from SDF1‐overexpressing MSCs display a beneficial effect on ischemic myocardial infarction. Initially, a gain‐of‐function study was performed to investigate the function of SDF1 in ischemic myocardial cells and cardiac endothelial cells. Coculture experiments were performed to measure potential exosomic transfer of SDF1 from MSCs to ischemic myocardial cells and cardiac endothelial cells. During the coculture experiments, exosome secretion was disrupted by neutral sphingomyelinase inhibitor GW4869 and upregulated exosomal SDF1 using SDF1 plasmid. Effects of Exo‐SDF1 on cardiac function in MI mice were investigated in vivo. MSCs suppressed myocardial cell apoptosis and promoted microvascular regeneration of endothelial cells through secretion of exosomes. The addition of GW4869 led to increased apoptotic capacity of myocardial cells, decreased microvascular formation ability of endothelial cells, enhanced autophagy ability, and elevated Beclin‐1 level as well as ratio of LC3II/LC3I. Overexpression of SDF1 and Exo‐SDF1 inhibited apoptosis and autophagy of myocardial cells, but promoted tube formation of endothelial cells. The interference of PI3K signaling pathway promoted apoptosis and autophagy of myocardial cells, but inhibited tube formation of endothelial cells. SDF1 activated the PI3K signaling pathway. Exo‐SDF1 protected cardiac function of MI mice and inhibited myocardial tissue damage. This study provided evidence that SDF1 overexpression in MSCs‐derived exosomes inhibited autophagy of ischemic myocardial cells and promoted microvascular production of endothelial cells.
Stromal‐derived factor 1 (SDF1) overexpression in mesenchymal stem cells (MSCs)‐derived exosomes inhibited autophagy of ischemic myocardial cells and promoted microvascular production of endothelial cells.
With the rapid development of asymmetric catalysis, the demand for the enantioselective synthesis of complex and diverse molecules with different chiral elements is increasing. Owing to the unique ...features of atropisomerism, the catalytic asymmetric synthesis of atropisomers has attracted a considerable interest from the chemical science community. In particular, introducing additional chiral elements, such as carbon centered chirality, heteroatomic chirality, planar chirality, and helical chirality, into atropisomers provides an opportunity to incorporate new properties into axially chiral compounds, thus expanding the potential applications of atropisomers. Thus, it is important to perform catalytic asymmetric transformations to synthesize atropisomers bearing multiple chiral elements. In spite of challenges in such transformations, in recent years, chemists have devised powerful strategies under asymmetric organocatalysis or metal catalysis, synthesizing a wide range of enantioenriched atropisomers bearing multiple chiral elements. Therefore, the catalytic asymmetric synthesis of atropisomers bearing multiple chiral elements has become an emerging field. This review summarizes the rapid progress in this field and indicates challenges, thereby promoting this field to a new horizon.
The catalytic asymmetric synthesis of atropisomers bearing multiple chiral elements has recently become an emerging research field. Chemists have devised metal‐catalyzed or organocatalytic asymmetric reactions for accessing atropisomers with multiple chiral elements, such as those with center chirality, planar chirality, and helical chirality. This review summarizes the rapid developments in this field and indicated the remaining challenges.
Summary of main observation and conclusion
A new class of axially chiral aryl‐alkene‐indole frameworks have been designed, and the first catalytic asymmetric construction of such scaffolds has been ...established by the strategy of organocatalytic (Z/E)‐selective and enantioselective (4+3) cyclization of 3‐alkynyl‐2‐indolylmethanols with 2‐naphthols or phenols (all >95 : 5 E/Z, up to 98% yield, 97% ee). This reaction also represents the first catalytic asymmetric construction of axially chiral alkene‐heteroaryl scaffolds, which will add a new member to the atropisomeric family. This approach has not only confronted the great challenges in constructing axially chiral alkene‐heteroaryl scaffolds but also provided a powerful strategy for the enantioselective construction of axially chiral aryl‐alkene‐indole frameworks.
The first catalytic asymmetric construction of axially chiral aryl‐alkene‐indole scaffolds has been established by a (4+3) cyclization of 3‐alkynyl‐2‐indolylmethanols with 2‐naphthols or phenols.
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