Palladium-catalyzed allylic C-H alkylation of terminal olefins with 3-carboxamide oxindoles.

A novel palladium-catalyzed allylic C-H alkylation of terminal olefins with 3-carboxamide oxindoles is described. A variety of new 3-carboxamide-3-allylation oxindoles with an all-carbon quaternary center were obtained in moderate to good yields (up to 99%). In addition, the asymmetric version of this reaction was also explored, providing moderate enantioselectivity.

New Triterpenoids from the Leaves of and Their Anti-Inflammatory Activity.

Six new triterpenoids, heritieras C-H (-), along with thirteen known triterpenoids (-), were isolated from the leaves of . Their structures were identified by spectroscopic analysis, including 1D and 2D nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HRESIMS), and by comparison with the literature. Anti-inflammatory activity of the isolates was evaluated using the lipopolysaccharide (LPS) stimulated RAW 264.

Key Kinetic Interactions between NO and Unsaturated Hydrocarbons: H Atom Abstraction from C-C Alkynes, Dienes, and Trienes by NO.

An adequate understanding of the NO interacting chemistry is a prerequisite for a smoother transition to carbon-lean and carbon-free fuels such as ammonia and hydrogen. In this regard, this study presents a comprehensive study on the H atom abstraction by NO from C to C alkynes, dienes, and trienes forming 3 HNO isomers (i.e.

Pd(OAc)-Catalyzed Synthesis of Imidazo[1,2-]phenanthridines via a Sequential Ullmann Coupling and Oxidative Coupling Dehydrogenation.

The Ullmann coupling and oxidative coupling dehydrogenation reactions have occurred sequentially, catalyzed by Pd(OAc), which unexpectedly yielded fused imidazo[1,2-]phenanthridine derivatives in good to high yields. Structural analysis of the intermediate and final products indicated that the protocol did not include C-H and N-H arylation.

Programmable Synthesis of Cationic Azaperylenes via Rh(III)-Catalyzed Multiple C-H/N-H Bonds Activation and Annulation.

Rh(III)-catalyzed dual N-H and triple C-H activation/(4 + 2) annulation of 2-aryl-2,3-dihydro-1-perimidines and alkynes has been disclosed to construct 4,5,14,15-tetrasubstituted cationic azaperylenes with high yields (up to 95%) and broad scope. Tandem (4 + 2) annulation of 1-perimidines with vinylene carbonate and alkynes affords 4,5-disubstituted azaperylene salts, and -alkynyl 1-perimidines undergo an intra- and intermolecular annulation cascade to give 4,5,14-trisubstituted targets. Most of the intermediates were detected by ESI-MS, indicating a convincible mechanism including three possible paths.

Bioinspired Synthesis of Phelligridin Analogues via Ru-Catalyzed C-H Activation/[4 + 2] Annulation of Aryl Imidates with Heteroaromatic Iodonium Ylides.

The first Ru(II)-catalyzed C-H activation/[4 + 2] annulation of aryl imidates with heteroaromatic iodonium ylides is reported. Our approach features the utilization of a commercially available ruthenium catalyst, providing a one-step construction of phelligridin analogues from easily available and nonpreactivated starting materials. The developed methodology is successfully employed for the total synthesis of phelligridin A, significantly streamlining previous multistep synthesis.

Dual impacts of serine/glycine-free diet in enhancing antitumor immunity and promoting evasion via PD-L1 lactylation.

The effect of the serine/glycine-free diet (-SG diet) on colorectal cancer (CRC) remains unclear; meanwhile, programmed death-1 (PD-1) inhibitors are less effective for most CRC patients. Here, we demonstrate that the -SG diet inhibits CRC growth and promotes the accumulation of cytotoxic T cells to enhance antitumor immunity. Additionally, we also identified the lactylation of programmed death-ligand 1 (PD-L1) in tumor cells as a mechanism of immune evasion during cytotoxic T cell-mediated antitumor responses, and blocking the PD-1/PD-L1 signaling pathway is able to rejuvenate the function of CD8+ T cells recruited by the -SG diet, indicating the potential of combining the -SG diet with immunotherapy.

Frustrated Lewis Pair-Mediated Cycloisomerization of Propargylaniline and Aryl Propargyl Ether Derivatives via a 6--dig Cyclization/Dehydrogenation Sequence.

An efficient FLP-mediated cycloisomerization is described, providing easy access to quinolinium and chromenylium derivatives by treatment of readily available propargylanilines and aryl propargyl ethers with Lewis acidic boranes, respectively. The reaction proceeds via a 6--dig cyclization/dehydrogenation sequence. The heteroatom functions serve as Lewis bases in combination with Lewis acidic boranes to effect synergistic activation of an alkynyl triple bond and a C-H bond.

Insight into the Pyrolysis Behaviors of Petroleum-Driven Mesophase Pitch via ReaxFF Molecular Dynamics and In Situ TG-FTIR/MS.

Mesophase pitch is regarded as a profoundly promising candidate for the production of advanced carbon-based multifunctional materials such as carbon fibers, carbon microspheres, and carbon foams owing to its excellent intrinsic properties. Consequently, a deeper understanding of pyrolytic chemistry is indispensable for the efficient and environmentally friendly utilization of mesophase pitch. In this study, details about the structure compositions and microscopic morphologies of petroleum-driven mesophase pitch (pMP) were investigated through ultimate, FTIR, XPS, and C-NMR analyses.

CAR-Macrophage Therapy Alleviates Myocardial Ischemia-Reperfusion Injury.

Background: Given the growing acknowledgment of the detrimental effects of excessive myocardial fibrosis on pathological remodeling after myocardial ischemia-reperfusion injury (I/R), targeting the modulation of myocardial fibrosis may offer protective and therapeutic advantages. However, effective clinical interventions and therapies that target myocardial fibrosis remain limited. As a promising chimeric antigen receptor (CAR) cell therapy, whether CAR macrophages (CAR-Ms) can be used to treat I/R remains unclear.

Palladium-Catalyzed Dearomative Heck/C(sp)-H Activation/Decarboxylative Cyclization of C2-Tethered Indoles.

Until now, palladium-catalyzed dearomative Heck reactions of indoles were largely limited to β-H elimination and nucleophilic capture of the transient alkyl-Pd(II) species. Herein, we disclose a novel palladium-catalyzed dearomative Heck/C(sp)-H activation/decarboxylative cyclization of C2-tethered indoles. In this protocol, the alkyl-Pd(II) species formed by dearomatization of C2-tethered indoles is not terminated by common β-H elimination or nucleophilic capture, but rather generates ,-palladacycle via C-H activation.

Enantioselective Electrocatalysis for Cross-Dehydrogenative Heteroarylation with Indoles, Pyrroles, and Furans.

Oxidative cross-dehydrogenative C-H/C-H functionalizations represent an exemplary approach for synthesizing carbonyl compounds via α-heteroarylation. Here we present the development of a direct anodic oxidative coupling process between 2-acylimidazoles and divergent heterocyclic systems including indole, pyrrole, and furan, facilitated by ferrocene-assisted asymmetric nickel electrocatalysis with high levels of enantioselectivity. Mechanistic investigations indicate that the reaction initially involves the formation of a chiral Ni-bound α-carbonyl radical, which is then captured by the heteroarene radical cation via intermolecular stereoselective radical/radical cation coupling.

Pd-Catalyzed Dual C-H Activation/Cyclization: Convergent and Divergent Synthesis of 1-Azahelicenes.

Herein, we report a convergent synthesis of 1-azahelicenes using easily available quinoline derivatives and cyclic diaryliodonium salts as starting materials. This reaction undergoes a palladium-catalyzed dual C-H activation/cyclization process to give facile access to a wide range of 1-aza[5]helicenes and 1-aza[6]helicenes with abundant functional groups (including F, Cl, Br, I, CF, SeR, SR, and heteroaryl) in moderate to excellent yields, thereby providing new opportunities to fine-tune the properties of the helicene backbone. In addition, the obtained products could be further transformed into helicene-based Lewis base catalysts and redox switch materials easily.

Palladium-Catalyzed Bicycloaromatization of -(Alkynyl)styrenes with Alkynes: Economical Access to Chrysene Derivatives.

Herein, a palladium-catalyzed bicycloaromatization of -(alkynyl)styrenes with alkynes is reported. In this protocol, the 6-- cyclization of -(alkynyl)styrenes is followed by deprotonation to complete the first cycloaromatization, and then, a regioselective alkyne insertion/C-H activation occurs to achieve the second cycloaromatization, resulting in atom- and step-economical syntheses of polysubstituted chrysenes. Notably, the products can be further used to construct π-extended arenes using the Scholl reaction.

Palladium/norbornene-catalyzed C-H/N-H cycloaddition of carbazoles with 2-halobenzoic acid derivatives.

An example of palladium/norbornene-catalyzed C-H/N-H cycloaddition of carbazoles with 2-bromobenzoic acids is presented, in which a collection of important carbazoles is expeditiously obtained. Derivatives, including acyl halides, α-oxocarboxylic acids, anhydrides, and even amides, are all allowed. Preliminary mechanistic studies reveal that a rare six-membered spiropalladacycle is involved.

A switch strategy for the synthesis of C4-ethylamine indole and C7-aminoindoline controllable carbon elimination.

Controllable β-carbon elimination to extrude norbornene remains a long-standing challenge in palladium and norbornene chemistry. Herein, this manuscript describes a switchable synthesis of biologically active C4-ethylaminoindole and C7-aminoindoline scaffolds by controlling β-carbon elimination, utilizing aziridine as a C-H ethylamination reagent through a C-N bond cleavage reaction. Furthermore, the protecting groups of the product can be easily removed, offering an unusual method for the synthesis of dopamine receptor agonists.

Main-group compounds selectively activate natural gas alkanes under room temperature and atmospheric pressure.

Most C-H bond activations of natural gas alkanes rely on transition metal complexes. Activations by using main-group systems have been reported but required heating or photo-irradiation under high atmospheric pressure with rather low regioselectivity. Here we report that Lewis acid-carbene adducts facilely undergo oxidative additions to C-H bonds of ethane, propane and n-butane with high selectivity under room temperature and atmospheric pressure.

Iron-Catalyzed C-H Arylphosphorylation of Quinoxalines.

A one-pot strategy for iron-catalyzed C2,3-H arylphosphorylation of electron-deficient quinoxalines with phosphines and aryl compounds is reported. The proposed method features the use of non-noble metal catalysts, the capacity of utilizing multiple aryl compounds as substrates, the simultaneous formation of C-P and C-C bonds in one pot, the simplicity of its operation, the mildness of the reaction conditions, and its compatibility with a wide range of substrates. Moreover, it offers a practical route for direct access to 2-aryl-3-phosphino -heteroarenes, a class of potential cyclometalated C^N and N^P bidentate ligands that are difficult to prepare with existing C(sp)-H functionalization methods.

Computational Design of Ligands for the Ir-Catalyzed C5-Borylation of Indoles through Tuning Dispersion Interactions.

The indole moiety is ubiquitous in natural products and pharmaceuticals. C-H borylation of the benzenoid moiety of indoles is a challenging task, especially at the C5 position. We have combined computational and experimental studies to introduce multiple noncovalent interactions, especially dispersion, between the substrate and catalytic ligand to realize C5-borylation of indoles with high reactivity and selectivity.

TsOH-catalyzed dehydroxylative cross-coupling of alcohols with phenols: rapid access to propofol derivatives.

Modification of the parent structure of molecules often alters their physicochemical properties and biological activities. Herein, a practical, efficient, and highly regioselective C-H alkylation of phenols with alcohols dehydroxylative cross-coupling was developed to produce -alkylated phenols with excellent regioselectivities and yields, using which propofol derivatives were rapidly synthesized. This process is performed under mild and simple conditions and is well-compatible with a variety of alcohols (secondary and tertiary benzylic alcohols as well as allyl alcohols) as alkylated agents.

Rh-Catalyzed C-H Alkynylation of Indole Derivatives with Silver(I)-Controlled Regiodivergence.

We have disclosed silver(I)-induced switching of regioselectivity in rhodium-catalyzed C-H alkynylation of indole derivatives with the help of a pivaloyl directing group by tuning C-H metalation modes. The judicious choice of AgOAc, AgO, and AgCO affords an array of C2-alkynylated indoles, C4-alkynylated indoles, and C2,C4-dialkynylated indoles, respectively. The synthetic utility of the alkyne fragment is demonstrated by derivatization into valuable indole-based compounds.

Double Direct C-H Bond Arylation of Thiophenes with Aryl Chlorides Catalyzed by the -Heterocyclic Carbene-PdCl-1-methylimidazole Complex.

With the combination of the -heterocyclic carbene-PdCl-1-methylimidazole complex and CuO, we succeeded in the first example of double direct C-H bond arylation reactions between thiophenes and aryl chlorides, giving the desired 2,5-diarylated thiophenes in moderate to high yields under suitable conditions, consistent with the density functional theory calculations.

A Cascade C(sp)-H Annulation Involving C(alkyl),C(alkyl)-Palladacycle Intermediates.

C-H bond functionalization involving C,C-palladacycle intermediates provides a unique platform for developing novel reactions. However, the vast majority of studies have been limited to the transformations of C(aryl),C-palladacycles. In sharp contrast, catalytic reactions involving C(alkyl),C(alkyl)-palladacycles have rarely been reported.