Synthesis and Antifungal Activity of Norbornene Carboxamide/sulfonamide Derivatives as Potential Fungicides Targeting Laccase

To explore more potential fungicides with new scaffolds, thirty-seven norbornene carboxamide/sulfonamide derivatives were designed, synthesized, and assayed for inhibitory activity against six plant pathogenic fungi and oomycetes. The preliminary antifungal assay suggested that the title derivatives showed moderate to good antifungal activity against six plant pathogens. Especially, compound 6 e presented excellent in vitro antifungal activity against Sclerotinia sclerotiorum (EC50=0.71 mg/L), which was substantially stronger than pydiflumetofen. In vivo antifungal assay indicated 6 e displayed prominent protective and curative effects on rape leaves infected by S. sclerotiorum. The preliminary mechanism research displayed that 6 e could damage the surface morphology and inhibit the sclerotia formation of S. sclerotiorum. In addition, the in vitro enzyme inhibition bioassay indicated that 6 e displayed pronounced laccase inhibition activity (IC50=0.63 μM), much stronger than positive control cysteine. Molecular docking elucidated the binding modes between 6 e and laccase. The bioassay results and mechanism investigation demonstrated that this class of norbornene carboxamide/sulfonamide derivatives could be promising laccase inhibitors for novel fungicide development.

Norbornene Copolymerization with Polar Monomers Catalyzed by Palladium Catalysts Containing Imidazolidin-2-imine/Guanidine Ligands

The development of a palladium catalyst that has enhanced catalytic performance, such as low aluminum cocatalyst loading, good copolymerization ability, high molecular weight, and excellent solubility of the (co)polymers, is still a challenge in norbornene copolymerizations. Here, a series of PdCl2 and PdMeCl complexes containing differently substituted anilines and imidazolidin-2-imine/guanidine ligands was successfully synthesized and characterized. X-ray diffraction analysis results revealed that these Pd complexes adopted an almost square-planar geometry, and the six-membered chelate ring showed structural distinctions as compared to traditional N^N-based α-diimine and β-diimine Pd complexes. These Pd complexes were activated by EtAlCl2 and then exhibited moderate activity (104-105 g mol-1 h-1) and good thermal stability (up to 90 °C) for norbornene polymerization to produce high-molecular-weight PNBs (Mn up to 96.4 kg mol-1) with narrow polydispersities (PDI as low as 1.39). These Pd complexes also exhibited good polar group tolerance in the copolymerization of norbornene with methyl 5-norbornene-2-carboxylate and methyl 10-undecenoate, in which the activity was achieved up to 7.04 × 104 g mol-1 h-1. It furnished polar functionalized norbornene-based copolymers with high molecular weight (Mn up to 63.1 kg mol-1), narrow PDI, reasonable polar monomer incorporation, and good solubility. These Pd catalysts exhibited an enhanced copolymerization ability to produce PNB or NB-based copolymers, representing significant progress in this field.

Photoresponsive Palladium and Nickel Catalysts for Ethylene Polymerization and Copolymerization

In this contribution, we install an azobenzene functionality in olefin polymerization catalysts and use light to modulate their properties via photoinduced trans-cis isomerization of the azobenzene moiety. The initially targeted azobenzene-functionalized α-diimine palladium and nickel catalysts are not photoresponsive. To address this issue, an imine-amine system bearing interrupted conjugation with the metal center, and a sandwich-type α-diimine system bearing an azobenzene unit at a position covalently far from the metal center were prepared and studied. We demonstrate that light can be used to tune their properties in ethylene polymerization and copolymerization with polar comonomers, enabling light-induced control of the polymerization processes, polymer microstructures and polymer properties. More interestingly, the light-mediated property changes were attributed to ligand electronic effects in one system and ligand steric effects in the other.

Design, synthesis, and characterization of vinyl-addition polynorbornenes with tunable thermal properties

Substituents were introduced onto addition polynorbornenes to modify their thermal properties. The resultant materials displayed depressed glass-transition temperatures, high decomposition temperatures, and could be melt-processed.

Neutral and cationic methallyl nickel complexes in alkene activation: a combined DFT, ESI-MS and chemometric approach

Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried out with isomeric neutral and cationic methallyl nickel complexes L1Ni(η3-C3H5) and [L1Ni(η3-C3H5)][B(ArF)4] in the presence of borane co-catalysts.

Homo- and copolymerization of norbornene using tridentate IzQO palladium catalysts with dimethylaminoethyl as a side arm

Rigid IzQO–Pd catalysts were synthesized by Rh(iii)-catalyzed C–H/alkyne annulation and applied for the homo- and copolymerizations of norbornene with polar vinyl monomers.

A simple and versatile nickel platform for the generation of branched high molecular weight polyolefins

The development of high-performance transition metal catalysts has long been a major driving force in academic and industrial polyolefin research. Late transition metal-based olefin polymerization catalysts possess many unique properties, such as the ability to generate variously branched polyolefins using only ethylene as the feedstock and the capability of incorporating polar functionalized comonomers without protecting agents. Here we report the synthesis and (co)polymerization studies of a simple but extremely versatile α-imino-ketone nickel system. This type of catalyst is easy to synthesize and modify, and it is thermally stable and highly active during ethylene polymerization without the addition of any cocatalysts. Despite the sterically open nature, these catalysts can generate branched Ultra-High-Molecular-Weight polyethylene and copolymerize ethylene with a series of polar comonomers. The versatility of this platform has been further demonstrated through the synthesis of a dinuclear nickel catalyst and the installation of an anchor for catalyst heterogenization.

Ligand–metal secondary interactions in phosphine–sulfonate palladium and nickel catalyzed ethylene (co)polymerization

Ligand secondary interactions and Lewis acid modulation are simultaneously achieved in palladium and nickel catalyzed ethylene polymerization and copolymerization.

Camphor-based phosphine-carbonyl ligands for Ni catalyzed ethylene oligomerization

Ni and Pd complexes of camphor-based phosphine-carbonyl ligands containing biaryl moiety are designed and synthesized. The Ni complexes can catalyze ethylene oligomerization and generate waxy higher olefins as well as oily lower olefins.

Copolymerization of Norbornene and Styrene with Anilinonaphthoquinone-Ligated Nickel Complexes

Poly(norbornene-co-styrene)s were synthesized by the use of anilinonaphthoquinone-ligated nickel complexes [Ni(C₁₀H₅O₂NAr)(Ph)(PPh₃): 1a, Ar = C₆H₃-2,6-ⁱPr; 1b, Ar = C₆H₂-2,4,6-Me; 1c, Ar = C₆H₅] activated with modified methylaluminoxane (MMAO) or B(C₆F₅)₃ in toluene. The effects of the cocatalysts were more significant than those of the nickel complexes, and MMAO gave higher activity than B(C₆F₅)₃. The structural characterizations of the products indicated the formation of statistical norbornene copolymers. An increase of the styrene ratio in feed led to an increase in the incorporated styrene (S) content of the resulting copolymer. The molecular weight of the copolymer decreased with increasing the S ratio in feed at 70 °C. The copolymerization activity, using MMAO as a cocatalyst, decreased with lowering of the temperature from 70 to 0 °C, accompanied by an increase in the molecular weight of the copolymer. The S incorporation up to 59% with M_n of 78,000 was achieved by the 1b-B(C₆F₅)₃ catalytic system. The glass transition temperatures of the norbornene (N)/S copolymers determined by differential scanning calorimetry, decreased from 329 to 128 °C according to the S content.

Nickel(II) and Palladium(II) Complexes Bearing an Unsymmetrical Pyrrole-Based PNN Pincer and Their Norbornene Polymerization Behaviors versus the Symmetrical NNN and PNP Pincers

Unsymmetrical pincers have been shown to be better than the corresponding symmetrical pincers in several catalysis reactions. A new unsymmetrical PNN propincer, 2-(3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole (1), was synthesized from pyrrole through Mannich bases in a good yield. In addition, the new byproduct 2-(3,5-dimethylpyrazolylmethyl)-5-(dimethylaminomethyl)- N-(hydroxymethyl)pyrrole was also isolated. The reaction of 1 with [PdCl₂(PhCN)₂] and Et₃N in toluene yielded [PdCl{C₄H₂N-2-(CH₂Me₂pz)-5-(CH₂PPh₂)-κ³ P,N,N}] (2). The analogous reaction between 1 and [NiCl₂(DME)] or NiX₂ (X = Br, I) in the presence of NEt₃ in acetonitrile afforded [NiX{C₄H₂N-2-(CH₂Me₂pz)-5-(CH₂PPh₂)-κ³ P,N,N}] (3; X = Cl, Br, I). All complexes were structurally characterized. The norbornene polymerization behaviors of the unsymmetrical pincer complexes 2 and 3 in the presence of MMAO or EtAlCl₂ were compared with those of the symmetrical pincer complexes chloro[2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrolido]palladium(II) (NNN), chloro[2,5-bis(diphenylphosphinomethyl)pyrrolido]palladium(II), and chloro[2,5-bis(diphenylphosphinomethyl)pyrrolido]nickel(II) (PNP) at different temperatures. The PNN and NNN complexes exhibited far greater activity on the order of 10⁷ g of PNB/mol/h, with quantitative yields in some cases, in comparison to the PNP pincer palladium and nickel complexes. This trend was also supported by the ⁱPr group substituted PNP nickel and palladium pincer complexes. These polymerization behaviors are explained using steric crowding around the metal atom with the support of NMR studies and suggested that the activity increases as the N_pyrazole donor increases. Polymers were characterized by ¹H NMR, IR, TGA, and powder XRD methods.

Lewis acids in situ modulate pyridazine-imine Ni catalysed ethylene (co)polymerisation

The Lewis acid-base interaction between B(iii) Lewis acids and the pyridazine moiety reduced the electron density from the Ni center and in situ modulated the pyridazine-imine nickel catalyzed ethylene (co)polymerisation.

Norbornene polymerization and copolymerization with 1-alkenes by neutral palladium complexes bearing aryloxide imidazolin-2-imine ligand

A series of novel aryloxide imidazolin-2-imine bidentate neutral Pd(ii) complexes with different substituents on the imidazolin-2-imine ligand were synthesized and characterized.

Homo- and copolymerization of norbornene with tridentate nickel complexes bearingo-aryloxide-N-heterocyclic carbene ligands

New pincer-type tridentate nickel catalysts bearingo-aryloxide-NHC ligands were applied to catalyze the copolymerization of norbornene and 1-octene at elevated temperature.

Mechanistic details of ethylene polymerization reaction using methallyl nickel(ii) catalysts

We present a mechanistic study of the ligand functionalization of bulky boron co-activators on neutral methallyl Ni(ii) catalysts for polyethylene production. This provides a blueprint for the development and design of catalysts with a high degree of tunability in a more efficient way.