查看更多>>摘要：Herein,we report an asymmetric two-component alkenyl Catellani reaction for the construction of C—N axial chirality through a palladium/chiral norbornene cooperative catalysis and an axial-to-axial chirality transfer process.Various partially aromatic iodinated 2-pyridones,quinolones,coumarin and uracil substrates react with 2,6-disubstituted aryl bromides with a tethered amide group,to afford a wide variety of polycyclic C—N atropisomers(38 examples,up to 97％e.e.).The obtained C—N axial chirality originates from the preformed transient C—C axial chirality with high fidelity.The synthetic utility of this chemistry is demonstrated by facile prepa-ration of complex quinoline and pyridine based C—N atropisomers through a N-deprotection and aromatization sequence.In addi-tion,a remote axial-to-central diastereoinduction process dictated by C—N axial chirality is observed with excellent diastereocontrol.
查看更多>>摘要：The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framework and has been utilized as an important toolbox due to their structural stability.Herein,we design and synthesize[2.2]paracyclophane-derived oxazole-pyrimidine ligands(abberviated as PYMCOX).These N,N-ligands with stable properties,rigid structure and large steric hindrance performed successfully in nickel-catalyzed asymmetric 1,2-reduction of α,β-unsaturated ketones,affording the chiral allylic alcohols with up to 99％yield and 99％ee.Meanwhile,this reduction reaction could be conducted on gram-scale without loss of activity and enantioselectivity,and the chiral ligand could be conveniently recovered with high yield.
查看更多>>摘要：Atroposelective synthesis of N-N atropisomers is an emerging area but remains underexplored;in particular,the synthesis of N-N benzimidazole atropisomers is still unprecedented.Herein,the first enantioselective synthesis of N-N benzimidazole atropisomers via the palladium-catalyzed de novo construction of benzimidazole skeleton is presented.With readily available palladium catalyst and biphosphine ligand,a broad range of nonbiaryl benzimidazole and indole-benzimidazole atropisomers were conveniently ac-cessed in high yields and with excellent enantioselectivities.Significantly,these N-N benzimidazole atropisomers showed great anti-tumor activity and selectivity to breast cancer MCF-7 cells.The simple catalytic system,broad substrate scope,high enantioselectivi-ty,and good bioactivity make this approach highly attractive.
查看更多>>摘要：A new approach to allylic alkylation is realized using an atomically dispersed palladium catalyst(Pd1/TiO2-EG).Unlike conventional methods that require derivation of substrates and utilization of additives,this method allows for direct allylic alkylation from allylic alcohols,producing H2O as the sole by-product.The catalyst's high efficiency is attributed to the local hydrogen bonding at the or-ganic-inorganic interface(Pd-EG interface),facilitating hydroxyl group activation for η3 π-allyl complex formation.The system demonstrates successful direct C—O and C—C coupling reactions with high selectivity,requiring no additives.This study highlights the potential of supported atomically dispersed catalysts for greener and more efficient catalysis,meanwhile,offers unique insights into the distinct behavior of atomically dispersed catalysts in comparison to homogeneous or nanoparticle-based catalysts.
查看更多>>摘要：The π-π interaction is acknowledged as the predominant factor to determine the molecular packing in organic photovoltaic materials,while other non-covalent intermolecular interactions especially the σ-π hyperconjugation are often ignored.Herein,a perylene diimide(PDI)derivative named FIDT-PDI is designed and synthesized to shed light into the effect of hyperconjugation on the molecular packing and further the photovoltaic performance.Dynamic NMR and 2D NOE NMR demonstrate the formation of intermolecular σ-πhyperconjugation between the C—H bond of the PDI moiety in one molecule and the phenyl sidechain in another molecule of FIDT-PDI.Benefiting from the σ-π hyperconjugation,FIDT-PDI with twisted backbone reversely exhibits more ordered packing and stronger crystallinity compared with another PDI derivative FIDTT-PDI which has better planarity,consequently achieving superior PCE and higher carrier mobility.This contribution is the first paradigm to unravel the structure-property relationship between σ-π hyper-conjugation of conjugated materials and corresponding photovoltaic performance.
查看更多>>摘要：Indole-based atropisomers are a very important class of axially chiral compounds.However,the atroposelective synthesis of axially chiral 2-arylindole remains largely unexplored.In this study,we report the successful synthesis of atropisomeric 2-arylindoles using direct amination of indoles with p-quinonediimines in the presence of chiral phosphoric acid as a catalyst.Quinonediimine acts as an aminating reagent through formal polarity inversion of imine.The malonate group on the 2-aryl of 2-indoles was found to be essen-tial for high enantioselectivity of the products.This could be due to the additional interaction between the ester group and the cata-lyst,as well as the intramolecular hydrogen bonding.Our findings provide a new strategy for the asymmetric construction of 2-arylindole atropisomers.
查看更多>>摘要：Reduction of chlorogermylene MsFluindtBu-GeCl 1 with potassium graphite(KC8)afforded putative germylyne radical MsFluindtBu-Ge 2 as confirmed by electron paramagnetic resonance(EPR)spectroscopy.However,it slowly decayed via C—H bond activation at the fluorenyl moiety to yield a bis(germylene)3 at room temperature.By using a Lewis base to stabilize the unoccupied p orbital at the GeⅠ radical center,acyclic two-coordinate GeⅠ radicals MsFluindtBu-Ge(IMe4)4(IMe4=1,3,4,5-tetramethyl-imidazolin-2-ylidene),MsFluindtBu-Ge(IiPr)5(IiPr=1,3-diisopropyl-4,5-dimethyl-imidazolin-2-ylidene),MsFluindtBu-Ge(PMe3)6 were isolated in crystalline forms.The unpaired electron in 4-6 mainly resides at the Ge 4p orbital as revealed by EPR spectroscopic studies and theoretical calculations.Interestingly,facile ligand exchange of PMe3 in 6 with IMe4 and IiPr was observed to afford 4 and 5,respectively.Moreover,phosphinogermylyne 6 reacted with PhEEPh(E=S,Se),4-tetrabutylphenylacetylene(Ar'CCH),[CpMo(CO)3]2 and nBu3SnH to furnish germylenes MsFluindtBu-GeEPh(E=S 7,Se 8),MsFluindtBu-GeCH=CHAr'9,a germylyne complex MsFluindtBu-Ge≡Mo(CO)2Cp 10 and a Ge(Ⅳ)compound MsFluindtBu-GeH2SnnBu311,respectively.The reactivity studies demonstrate that 6 can act as a synthon of one-coordinate germylyne radical attributing to labile coordination of trimethylphosphine.
查看更多>>摘要：Psoriasis is a chronic immune-mediated inflammatory skin disease and the TNF-α is an important therapeutic target of this disease.In our continuous study of bioactive natural products from fungi,the first ergosterol-polyether adducts,polyaspers A(1)and B(2),along with two known ergosterols,(36,5α,6α,22E)-5,6-epoxy-3-hydroxyergosta-8,22-dien-7-one(3)and calvasterol B(4),were iso-lated from Aspergillus sp.TJ507.Structure elucidation was accomplished by extensive spectroscopic analysis and single-crystal X-ray diffraction tests.Polyaspers A and B possessing an unequalled 6/6/6/5/5/6/6/6/6 nonacyclic system,and their biosynthetic path-ways were proposed to include intermolecular cyclization and Diels-Alder reactions.Activity screen of these isolates showed that 1-3 could improve the cell viability in an actinomycin D/TNF-α induced L929 cells death model,with the EC50 values of 49.85,46.75 and 4.99 μmol/L,respectively,and the activity of 3 was even comparable with that of the positive control SPD304.Further bioactive investigations discovered 3 could suppress the inflammatory response simulated with TNF-α in HaCaT cells.In an imiquimod-induced psoriasis murine model,3 significantly restrained the development of psoriasis symptoms and reduced the expression of IL-17 and IL-23,presenting an anti-psoriatic effect.As such,those ergosterol derivatives,might serve as lead compounds for the development of novel TNF-α inhibitory agents in the clinical treatment of psoriasis.
查看更多>>摘要：Developing novel unfused building blocks with simple synthesis and low cost is essential to advance and enrich cost-effective poly-mer donors;however,it remains a challenge due to the lack of efficient molecular strategies.Herein,a class of low-cost and fully unfused polymer donors with precisely regulated backbone planarity via halogenation was designed and synthesized,namely PDTBTBz-2H,PDTBTBz-2F,and PDTBTBz-2Cl.These polymer donors possess a four-step synthesis route with over 80％yield from cheap raw chemicals comparable to existing low-cost polymer donors,such as PTQ10.Benefitting from the planar backbone via in-corporating the F…S non-covalent interactions,PDTBTBz-2F exhibits more robust J-type aggregation in solution and a long-ranged molecular stacking in film relative to PDTBTBz-2H and PDTBTBz-2Cl.Moreover,the systematical study of PDTBTBz-based organic so-lar cells(OSCs)reveals the close relationship between optimized molecular self-assembly and charge separation/transport regarding backbone halogenation when paired with the non-fullerene acceptor(Y6-BO-4F).As a result,the photovoltaic devices based on semicrystalline PDTBTBz-2F achieved a promising power conversion efficiency(PCE)of 12.37％.Our work highlighted the influence of backbone halogenation on the molecular self-assembly properties and a potential unfused backbone motif for further developing cost-effective OSCs.
查看更多>>摘要：α-Olefins as aliphatic terminal alkenes could be obtained easily from numerous contemporary synthetic reactions as well as petro-chemical industry,and also found in natural products.Compared to the alkenes attaching the directing groups or activating group,the catalytic asymmetric reaction of unactivated terminal alkenes presents great challenges due to the weak electron effect and small steric hindrance effect.This review mainly summarizes the latest progress of the asymmetric reaction of unactivated terminal olefins since 2016.
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