Ligand-controlled NiH-catalyzed regiodivergent hydroalkylation of 2-alkenylazaarenes

A nickel-hydride(Ni H)-catalyzed migratory and nonmigratory hydroalkylation reaction of 2-alkenyl azaarenes with alkyl iodines has been established through strategic modulation of N-or P-donor ligands.This method enables the synthesis of diverseβ-orγ-branched aromatic N-heterocycles.The mild regiodivergent protocols exhibit wide substrate scope,excellent functional tolerance,and great reaction yield with remarkable regioselectivity.Importantly,deuterium labeling studies reveal Ni H-catalyzed interrupted chain-walking mode as the mechanism behind remotedβ-selective hydroalkylation reaction—an interesting phenomenon mediated through aromatic imine directing groups.

Palladium-Catalyzed One-Step Synthesis of Stereodefined Difunctionalized Glycals

Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain modified glycals in one step through palladium catalysis was reported for the first time,and the modified glycals contained stereodefined tetrasubstituted olefins.Using this method,various difunctionalized glycals that were difficult to form by other routes were synthesized in moderate to good yields.Control experiments and density functional theory calculations show that the palladium catalyst played dual roles in this transformation,namely,inducing nucleophilic substitution and catalyzing Suzuki coupling.The reaction intermediate was isolated and confirmed by X-ray crystallographic analysis.Furthermore,the gram-scale synthesis and facile deprotection of the target compound enhances the practicality of this strategy.

Constructing a biomimetic robust bi-layered hydrophilic lubrication coating on surface of silicone elastomer

Silicone elastomers-based materials have been extensively involved in the field of biomedical devices,while their use is extremely restricted due to the poor surface lubricity and inherent hydrophobicity.This paper describes a novel strategy for generating a robust layered soft matter lubrication coating on the surface of the polydimethylsiloxane(PDMS)silicone elastomer,by entangling thick polyzwitterionic polyelectrolyte brush of poly(sulfobetaine methacrylate)(PSBMA)into the sub-surface of the initiator-embedded stiff hydrogel coating layer of P(AAm-co-AA-co-HEMA-Br)/Fe,to achieve a unified low friction and high load-bearing properties.Meanwhile,the stiff hydrogel layer with controllable thickness is covalently anchored on the surface of PDMS by adding iron powder to provide catalytic sites through surface catalytically initiated radical polymerization(SCIRP)method and provides high load-bearing capacity,while the topmost brush/hydrogel composite layer is highly effective for aqueous lubrication.Their synergy effects are capable of attaining low friction coefficient(COFs)under wide range of loaded condition in water environment with steel ball as sliding pair.Furthermore,the influence of mechanical modulus of the stiff hydrogel layer on the lubrication performance of layered coating is investigated,for which the COF is the lowest only when the modulus of the stiff hydrogel layer well matches the PDMS substrate.Surprisingly,the COF of the modified PDMS could remain low friction(COF<0.05)stably after encountering 50,000 sliding cycles under 10 N load.Finally,the surface wear characterizations prove the robustness of the layered lubricating coating.This work provides a new route for engineering lubricious silicon elastomer with low friction,high load-bearing capacity,and considerable durability.

Reductive Coupling of Aryl Halides via C-H Activation of Indene

This paper describes the first case of a reductive coupling reaction with indene,a non-heteroatom olefin used as a reducing agent.The scope of the substrate is wide.The homo-coupling,cross-coupling,and synthesis of 12 and 14-membered rings were realized.The control experiment,indene-product curve and density functional theory calculations showed that the η^(3)-palladium indene intermediate was formed by C-H activation in the presence of cesium carbonate.We speculate that the final product was obtained through a Pd(IV)intermediate or aryl ligand exchange.In addition,we excluded the formation of palladium anion(Pd(0)^(-))intermediates.