Twofold C−H annulation of readily available formamides and alkynes without built‐in chelating groups was achieved. Ni−Al bimetallic catalysis enabled by a bulky BINOL‐derived chiral secondary ...phosphine oxide (SPO) ligand proved to be critical for high reactivity and high selectivity. This reaction uses readily available formamides as starting materials and provides a concise synthetic pathway to a broad range of chiral ferrocenes in 40–98 % yield and 93–99 % ee.
Two for Two: A highly enantioselective annulation of two C−H bonds with alkynes without built‐in chelating groups was achieved through Ni−Al bimetallic catalysis enabled by a bulky BINOL‐derived secondary phosphine oxide (SPO) ligand. This reaction uses readily available formamides as starting materials and provides concise access to a broad range of chiral ferrocenes in 40–98 % yield and 93–99 % ee.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Due to the strong electron‐withdrawing nature and high lipophilicity of trifluoromethoxy group (OCF3), methods for introducing OCF3 into organic molecules are in high demand. However, the research ...area of direct enantioselective trifluoromethoxylation is still in the embryonic stage, with limited enantioselectivity and/or reaction types. Here, we describe the first copper‐catalyzed enantioselective trifluoromethoxylation of propargyl sulfonates using trifluoromethyl arylsulfonate (TFMS) as the trifluoromethoxy source in up to 96 % ee.
Currently, great challenges still remain for direct asymmetric trifluoromethoxylation with only two successful reports since the first discovery. Here, by subtly tuning the leaving group, protecting group, ligand structure, reaction temperature, solvent and base, we finally realized a copper‐catalyzed enantioselective trifluoromethoxylation of propargyl sulfonates for the first time.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Compared with non-ligated Ni-Al bimetallic catalysis, bifunctional ligand-ligated Ni-Al bimetallic catalysis displays stronger synergism, not only affecting the electronic properties and steric ...hindrance of substrates, but also producing a directing effect for facile control of reactivity, site selectivity and enantioselectivity in the activation of C-H and C-C bonds. This review will give a brief summary of research advances in this field, highlighting the development of bifunctional ligands and their applications.
Ligand-ligated Ni-Al bimetallic catalysis not only affects electronic and steric property of substrates, but also produces strong directing effect for facile control of reactivity and selectivity in the activation of C-H and C-C bonds.
A chiral aluminum complex controlled, enantioselective nickel‐catalyzed domino reaction of aryl nitriles and alkynes proceeding by C−CN bond activation was developed. The reaction provides various ...indenes, bearing chiral all‐carbon quaternary centers, under mild reaction conditions in yields of 32 to 91 % and ee values within the 73–98 % range. The reaction mechanism and aspects of stereocontrol were investigated by DFT calculations.
Al takes control: A chiral aluminum complex controlled, enantioselective nickel‐catalyzed domino reaction of aryl nitriles and alkynes proceeding by C−CN bond activation was developed. The reaction provides various indenes, bearing chiral all‐carbon quaternary centers, under mild reaction conditions in good yields and with good ee values. The reaction mechanism and aspects of stereocontrol were investigated by DFT calculations.
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WRKY transcription factors are key regulatory components of plant responses to biotic and abiotic stresses. SpWRKY1, a pathogen‐induced WRKY gene, was isolated from tomato (Solanum pimpinellifolium ...L3708) using in silico cloning and reverse transcriptase‐polymerase chain reaction (RT‐PCR) methods. SpWRKY1 expression was significantly induced following oomycete pathogen infection and treatment with salt, drought, salicylic acid (SA), methyl jasmonate (MeJA) and abscisic acid (ABA). Overexpression of SpWRKY1 in tobacco conferred greater resistance to Phytophthora nicotianae infection, as evidenced by lower malondialdehyde (MDA) content; relative electrolyte leakage (REL); higher chlorophyll content; and higher peroxidase (POD, EC 1.11.1.7), superoxide dismutase (SOD, EC 1.15.1.1) and phenylalanine ammonia‐lyase (PAL, EC 4.3.1.24) activities. This resistance was also coupled with enhanced expression of SA‐ and JA‐associated genes (NtPR1, NtPR2, NtPR4, NtPR5 and NtPDF1.2), as well as of various defense‐related genes (NtPOD, NtSOD and NtPAL). In addition, transgenic tobacco plants also displayed an enhanced tolerance to salt and drought stresses, mainly demonstrated by the transgenic lines exhibiting lower accumulation of MDA content and higher POD (EC 1.11.1.7), SOD (EC 1.15.1.1) activities, chlorophyll content, photosynthetic rate and stomatal conductance, accompanied by enhanced expression of defense‐related genes (NtPOD, NtSOD, NtLEA5, NtP5CS and NtNCED1) under salt and drought stresses. Overall, these findings suggest that SpWRKY1 acts as a positive regulator involved in tobacco defense responses to biotic and abiotic stresses.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Allylic amines are versatile building blocks in organic synthesis and exist in bioactive compounds, but their synthesis via hydroaminoalkylation of alkynes with amines has been a formidable ...challenge. Here, we report a late transition metal Ni-catalyzed hydroaminoalkylation of alkynes with N-sulfonyl amines, providing a series of allylic amines in up to 94% yield. Double ligands of N-heterocyclic carbene (IPr) and tricyclohexylphosphine (PCy
) effectively promote the reaction.
Achieving the transition metal-catalysed pyridine C3-H alkenylation, with pyridine as the limiting reagent, has remained a long-standing challenge. Previously, we disclosed that the use of strong ...coordinating bidentate ligands can overcome catalyst deactivation and provide Pd-catalysed C3 alkenylation of pyridines. However, this strategy proved ineffective when using pyridine as the limiting reagent, as it required large excesses and high concentrations to achieve reasonable yields, which rendered it inapplicable to complex pyridines prevalent in bioactive molecules. Here we report that a bifunctional N-heterocyclic carbene-ligated Ni-Al catalyst can smoothly furnish C3-H alkenylation of pyridines. This method overrides the intrinsic C2 and/or C4 selectivity, and provides a series of C3-alkenylated pyridines in 43-99% yields and up to 98:2 C3 selectivity. This method not only allows a variety of pyridine and heteroarene substrates to be used as the limiting reagent, but is also effective for the late-stage C3 alkenylation of diverse complex pyridine motifs in bioactive molecules.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
C‐aryl glycosides are popular basic skeletons in biochemistry and pharmaceutical chemistry. Herein, ruthenium‐catalyzed highly stereo‐ and site‐selective ortho‐ and meta‐CAr−H glycosylation is ...described. A series of C‐aryl pyranosides and furanosides were synthesized by this method. The strategy showed good substrate scope, and various N‐heterocyclic directing groups were compatible with the reaction system. A mechanistic study suggested that the key pathway of ortho‐CAr−H glycosylation might involve oxidative addition/reduction elimination, whereas aryl meta‐C−H glycosylation was mediated by σ‐activation. Density functional theory calculations also showed that the high stereoselectivity of meta‐CAr−H glycosylation was due to steric hindrance.
A series of C‐aryl pyranosides and furanosides were synthesized by ruthenium‐catalyzed ortho‐ and meta‐CAr−H glycosylation. Mechanistic studies suggest that the key pathway of ortho‐CAr−H glycosylation involves an oxidative addition/reductive elimination process, while aryl meta‐C−H glycosylation is mediated by σ‐activation. DFT calculations showed that steric hindrance is responsible for the high stereoselectivity of meta‐CAr−H glycosylation.
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•Relevant progress on transition metal-mediated or catalyzed hydrocarboxylations of alkenes.•Two main pathways of hydrocarboxylations of alkene with CO2 are reviewed.•Key ...intermediates in each step of catalytic cycles are highlighted.
The development of new methods to incorporate carbon dioxide into organic molecules is of special significance and interest as it is an abundantly available and recyclable C1 source. Catalytic hydrocarboxylation of readily available olefins with CO2 represents a highly atom- and step-economic approach toward transformations of CO2 into widely-used aliphatic acids. However, due to relatively lower reactivity of them, this goal has been always a formidable challenge. Herein we review relevant progress on transition metal-mediated or catalyzed methodologies toward the desired hydrocarboxylation, with an emphasis on the development of two main pathways, including transition-metal-catalyzed cyclometallation of olefin and CO2 and direct addition of alkylmetal to CO2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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