A novel radical 1,2‐formylfunctionalization of alkenes involving 1,2(4,5)‐formyl migration triggered by addition of various carbon‐ and heteroatom‐centered radicals to alkenes has been developed for ...the first time, thus providing straightforward access to diverse β‐functionalized aldehydes with good efficiency, remarkable selectivity, and excellent functional group tolerance. Analogous transformations mediated by a keto‐carbonyl migration have also been effected under similar conditions. This method was used to access ring systems including various benzannulated nine‐, ten‐, and eleven‐membered rings, complex 6‐5(6,7)‐6(5) fused rings, and bridged rings with diverse functionalities.
The old 1,2: A novel 1,2‐formyl functionalization of unactivated alkenes involving formyl migration and addition of radicals to alkenes has been developed for access to synthetically important β‐functionalized aldehydes. The analogous keto‐carbonyl migration has been performed to synthesize challenging medium‐sized diketones, which were additionally transformed into complex fused rings.
The development of circularly polarized electroluminescence (CPEL) is currently hampered by the high difficulty and cost in the syntheses of suitable chiral materials and the notorious chirality ...diminishment issue in electrical devices. Herein, diastereomeric IrIII and RuII complexes with chiral (±)‐camphorsulfonate counteranions are readily synthesized and used as the active materials in circularly polarized light‐emitting electrochemical cells to generate promising CPELs. The addition of the chiral ionic liquid (±)‐1‐butyl‐3‐methylimidazole camphorsulfonate into the active layer significantly improves the device performance and the electroluminescence dissymmetry factors (≈10−3), in stark contrast to the very weak circularly polarized photoluminescence of the spin‐coated films of these diastereomeric complexes. Control experiments with enantiopure IrIII complexes suggest that the chiral anions play a dominant role in the electrically‐induced amplification of CPELs.
By using a chiral anion strategy, electrically amplified circularly polarized luminescence (CPL) is realized in light‐emitting electrochemical cells of readily obtained diastereomeric ionic transition‐metal complexes. The addition of a chiral ionic liquid (IL) into the active layer significantly improves the device performance and the electroluminescence dissymmetry factors.
The development and applications of materials with efficient circularly polarized luminescence (CPL) have become an interdisciplinary frontier research topic. We summarize herein the recent advance ...in the development and applications of CPL‐active aggregates based on metal‐ligand coordination materials (termed as “coordination aggregates”). The materials surveyed are classified as aggregates of small‐molecular metal complexes, which include monocomponent assemblies of Pt(II) complexes and other complexes and binary aggregates of metal complexes, and CPL‐active metal‐ligand coordination helicates, polymers, and frameworks. The efforts in improving the dissymmetry luminescence factors and quantum yields of these materials and the use of the aggregation strategy in enhancing the performance of isolated molecules are discussed. The recent applications of chiral metal complexes in circularly polarized organic light‐emitting diodes (OLEDs) based on solution‐ or evaporation‐processed procedures are surveyed. In addition, the uses of lanthanide complexes in CPL‐contrast imaging and as CPL probes are highlighted. The common discussion on the mechanism of aggregation‐enhanced CPLs and a perspective on future works of CPL‐active coordination aggregates are finally given.
The recent progress in the development of circularly polarized luminescence (CPL)‐active aggregates of metal‐ligand coordination materials is summarized, including those based on discrete chiral metal complexes, chiral metal‐ligand helicates, and coordination polymers and frameworks. The applications of these materials in circularly polarized organic light‐emitting diodes and CPL‐contrast imaging and probes are further discussed.
Transition metal-catalyzed enantioselective Sonogashira-type oxidative C(sp
)-C(sp) coupling of unactivated C(sp
)-H bonds with terminal alkynes has remained a prominent challenge. The difficulties ...mainly stem from the regiocontrol in unactivated C(sp
)-H bond functionalization and the inhibition of readily occurring Glaser homocoupling of terminal alkynes. Here, we report a copper/chiral cinchona alkaloid-based N,N,P-ligand catalyst for asymmetric oxidative cross-coupling of unactivated C(sp
)-H bonds with terminal alkynes in a highly regio-, chemo-, and enantioselective manner. The use of N-fluoroamide as a mild oxidant is essential to site-selectively generate alkyl radical species while efficiently avoiding Glaser homocoupling. This reaction accommodates a range of (hetero)aryl and alkyl alkynes; (hetero)benzylic and propargylic C(sp
)-H bonds are all applicable. This process allows expedient access to chiral alkynyl amides/aldehydes. More importantly, it also provides a versatile tool for the construction of chiral C(sp
)-C(sp), C(sp
)-C(sp
), and C(sp
)-C(sp
) bonds when allied with follow-up transformations.
Conspectus Asymmetric functionalization of alkyl radicals represents a robust yet underdeveloped method for efficient construction and decoration of carbon skeletons in chiral organic molecules. In ...this field, we have been inspired by the excellent redox, alkyl radical trapping, and Lewis acidic properties of copper to develop several catalytic modes for asymmetric reactions involving alkyl radicals. At the beginning, we discovered tandem radical hydrotrifluoromethylation of unactivated alkenes and enantioselective alkoxylation of remote C(sp3)–H bonds by copper/chiral phosphate relay catalysis. This success has stimulated us to develop an asymmetric three-component 1,2-dicarbofunctionalization of 1,1-diarylalkenes using a similar strategy via radical intermediates. Meanwhile, we also discovered a copper/chiral secondary amine cooperative catalyst for asymmetric radical intramolecular cyclopropanation of alkenes using α-aldehyde methylene groups as C1 sources. The trapping of alkyl radical intermediates by CuII species during the reaction was essential for the chemoselectivity toward cyclopropanation. Encouraged by the efficient enantiocontrol with chiral phosphate and the effective trapping of alkyl radicals with CuII species, we then sought to develop copper/chiral phosphate as a single-electron-transfer catalyst for asymmetric reactions involving alkyl radicals. Subsequently, we successfully achieved a series of highly enantioselective 1,2-aminofluoroalkylation, -aminoarylation, -diamination, -aminosilylation, and -oxytrifluoromethylation of unactivated alkenes. The key for high enantioinduction was believed to be the effective trapping of alkyl radicals by CuII/chiral phosphate complexes. Besides, an achiral pyridine ligand was found to be indispensable for achieving high enantioselectivity, presumably via stabilization of CuIII species in the 1,2-alkoxytrifluoromethylation reaction. This discovery reminded us of tuning the redox properties and chemoreactivity of copper centers with an ancillary ligand. As a result, we subsequently identified cinchona alkaloid-derived sulfonamides as novel neutral-anionic hybrid ligands for simultaneous chemo- and enantiocontrol. We thus accomplished highly enantioselective 1,2-iminoxytrifluoromethylation of unactivated alkenes under the catalysis of copper/cinchona alkaloid-derived sulfonamide ligand, affording trifluoromethylated isoxazolines in high enantiomeric excess. Our copper-catalyzed asymmetric reactions with alkyl radicals provide expedient access to a diverse range of valuable chiral molecules with broad application potential in areas of organic synthesis, medicine, agrochemical, and material sciences.
Recently, chiral metal‐organic coordination materials have emerged as promising candidates for a wide range of applications in chiroptoelectronics, chiral catalysis, and information encryption, etc. ...Notably, the chiroptical effect of coordination chromophores makes them appealing for applications such as photodetectors, OLEDs, 3D displays, and bioimaging. The direct synthesis of chiral coordination materials using chiral organic ligands or complexes with metal‐centered chirality is very often tedious and costly. In the case of ionic coordination materials, the combination of chiral anions with cationic, achiral coordination compounds through noncovalent interactions may endow molecular materials with desirable chiroptical properties. The use of such a simple chiral strategy has been proven effective in inducing promising circular dichroism and/or circularly polarized luminescence signals. This concept article mainly delves into the latest advances in exploring the efficacy of such a chiral anion strategy for transforming achiral coordination materials into chromophores with superb photo‐ or electro‐chiroptical properties. In particular, ionic small‐molecular metal complexes, metal clusters, coordination supramolecular assemblies, and metal‐organic frameworks containing chiral anions are discussed. A perspective on the future opportunities on the preparation of chiroptical materials with the chiral anion strategy is also presented.
Taking advantage of the chirality transfer from chiral anions to cationic coordination components, efficient circular dichroism and circularly polarized luminescence properties are realized. Such a chiral anion strategy is successfully implemented in ionic small‐molecular metal complexes, metal clusters, coordination supramolecular assemblies, and metal‐organic frameworks. The chiroptical properties can be modulated by the use of different chiral anions.
In this paper, we deal with the problem of tracking control for a class of uncertain nonlinear systems in strictfeedback form subject to completely unknown system nonlinearities, hard constraints on ...full states, and unknown time-varying bounded disturbances. Integral barrier Lyapunov functionals are constructed to handle the unknown affine control gains (g(·)) with state constraints simultaneously. This removes the need on the knowledge of control gains for control design and avoids the conservative step of transforming original state constraints into new bounds on tracking errors. Neural networks (NNs) are used to approximate the unknown continuous packaged functions. To enhance the robustness, adapting parameters are developed to compensate the unknown bounds on NNs approximations and external disturbances. Design parameters-dependent feasibility conditions are formulated as sufficient conditions for the existence of feasible design parameters to guarantee the state constraints, and an offline constrained optimization step is proposed to obtain the optimal design parameters prior to the implementation of the proposed control. It is proved that the proposed control can guarantee the semiglobal uniform ultimate boundedness of all signals in closed-loop system, all states are ensured to remain in the predefined constrained state space, and tracking error converges to an adjustable neighborhood of the origin by choosing appropriate design parameters. Simulations are performed to validate the proposed control.
Continued development of the Sonogashira coupling has made it a well established and versatile reaction for the straightforward formation of C-C bonds, forging the carbon skeletons of broadly useful ...functionalized molecules. However, asymmetric Sonogashira coupling, particularly for C(sp
)-C(sp) bond formation, has remained largely unexplored. Here we demonstrate a general stereoconvergent Sonogashira C(sp
)-C(sp) cross-coupling of a broad range of terminal alkynes and racemic alkyl halides (>120 examples) that are enabled by copper-catalysed radical-involved alkynylation using a chiral cinchona alkaloid-based P,N-ligand. Industrially relevant acetylene and propyne are successfully incorporated, laying the foundation for scalable and economic synthetic applications. The potential utility of this method is demonstrated in the facile synthesis of stereoenriched bioactive or functional molecule derivatives, medicinal compounds and natural products that feature a range of chiral C(sp
)-C(sp/sp
/sp
) bonds. This work emphasizes the importance of radical species for developing enantioconvergent transformations.
Reported is a novel two‐step ring‐expansion strategy for expeditious synthesis of all ring sizes of synthetically challenging (hetero)aryl‐fused medium‐sized lactams from readily available ...5–8‐membered cyclic ketones. This step‐economic approach features a remote radical (hetero)aryl migration from C to N under visible‐light conditions. Broad substrate scope, good functional‐group tolerance, high efficiency, and mild reaction conditions make this procedure very attractive. In addition, this method also provides expedient access to 13–15‐membered macrolactams upon an additional one‐step manipulation. Mechanistic studies indicate that the reaction involves an amidyl radical and is promoted by acid.
Growth rings: A two‐step ring‐expansion strategy for expedient synthesis of all ring sizes of synthetically challenging (hetero)aryl‐fused medium‐sized lactams from readily available 5–8‐membered cyclic ketones has been developed. The key step involves an uncommon remote radical (hetero)aryl migration from C to N by C−C bond cleavage under irradiation with visible light.
In contrast to the wealth of asymmetric transformations for generating central chirality from alkyl radicals, the enantiocontrol over the allenyl radicals for forging axial chirality represents an ...uncharted domain. The challenge arises from the unique elongated linear configuration of the allenyl radicals that necessitates the stereo‐differentiation of remote motifs away from the radical reaction site. We herein describe a copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes via the coupling of allenyl radicals with terminal alkynes, providing diverse synthetically challenging tetrasubstituted chiral allenes. A chiral N,N,P‐ligand is crucial for both the reaction initiation and the enantiocontrol over the highly reactive allenyl radicals. The reaction features a broad substrate scope, covering a variety of (hetero)aryl and alkyl alkynes and 1,3‐enynes as well as radical precursors with excellent functional group tolerance.
A copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes is realized, providing diverse tetrasubstituted chiral allenes. The utilization of the copper/chiral N,N,P‐ligand is crucial for the enantiocontrol over the allenyl radicals, which is difficult due to their elongated linear configuration that necessitates the stereo‐differentiation of remote motifs away from the reaction site.
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