A hydrated regular cellulose paper filter modified with nanofibrillated cellulose (NFC) hydrogel was successfully fabricated for water/oil separation. The fabricated filter's hydrophilic and oleophobic properties resulted in increased filter life and decreased environmental impact, while displaying water flux of 89.6 L h(-1) m(-2) with efficiency ≥99% under gravitational force.

A directed, regiocontrolled hydroamination of unactivated terminal and internal alkenes is reported. The reaction is catalyzed by palladium(II) acetate and is compatible with a variety of nitrogen nucleophiles. A removable bidentate directing group is used to control the regiochemistry, prevent β-hydride elimination, and stabilize the nucleopalladated intermediate, facilitating a protodepalladation event. This method affords highly functionalized γ-amino acids in good yields with high regioselectivity.

Reactions that forge carbon-carbon (C-C) bonds are the bedrock of organic synthesis, widely used across the chemical sciences. We report a transformation that enables C-C bonds to be constructed from two classes of commonly available starting materials, alkenes and carbon-hydrogen (C-H) bonds. The reaction employs a palladium(II) catalyst and utilizes a removable directing group to both control the regioselectivity of carbopalladation and enable subsequent protodepalladation. A wide range of alkenes and C-H nucleophiles, including 1,3-dicarbonyls, aryl carbonyls, and electron-rich aromatics, are viable reaction partners, allowing Michael-type reactivity to be expanded beyond α,β-unsaturated carbonyl compounds to unactivated alkenes. Applications of this transformation in drug diversification and natural product total synthesis are described. Stoichiometric studies support each of the proposed steps in the catalytic cycle.

Palladium-catalyzed cross-coupling reactions between benzyl, aryl, or allyl bromides and conjugated ene-yne-ketones lead to the formation of 2-alkenyl-substituted furans. This novel coupling reaction involves oxidative addition, alkyne activation-cyclization, palladium carbene migratory insertion, β-hydride elimination, and catalyst regeneration. Palladium (2-furyl)carbene is proposed as the key intermediate, which is supported by DFT calculations. The palladium carbene character of the key intermediate is validated by three aspects, including bond lengths, Wiberg bond order indices, and molecular orbitals, by comparison to those reported for stable palladium carbene species. Computational studies also revealed that the rate-limiting step is ene-yne-ketone cyclization, which leads to the formation of the palladium (2-furyl)carbene, while the subsequent carbene migratory insertion is a facile process with a low energy barrier (<5 kcal/mol).

A palladium(II)-catalyzed 1,2-dicarbofunctionalization reaction of unactivated alkenes has been developed, wherein a cleavable bidentate directing group is used to control the regioselectivity and stabilize the putative alkylpalladium(II) intermediate. Under the optimized reaction conditions, a broad range of nucleophiles and electrophiles were found to participate in this transformation, providing moderate to high yields. 3-Butenoic acid derivatives containing internal alkenes and α-substituents were reactive substrates, offering a powerful platform for preparing β,γ-substituted carbonyl compounds with multiple stereocenters.

Ir(III)-catalyzed coupling of aromatic C-H bonds with diazomalonates has been achieved successfully via a metal carbene migratory insertion process. With different types of carbamoyl directing groups, a wide range of arenes, including heteroarenes, can be used as substrates in this Ir(III)-catalyzed C-H functionalization reaction. Mono- and bisfunctionalized products can be obtained selectively simply by changing the number of equivalents of the diazo substrate. Moreover, when diazomalonates bearing one or two tert-butyl groups are used as the substrates, the C-H bond functionalization is followed by decarboxyation, leading to products with a -CH2CO2Me or -CH2CO2H moiety at the position ortho to the directing group. This reaction demonstrates that direct C-H activation and the metal carbene migratory insertion can be merged into one catalytic cycle with an Ir(III) complex as the catalyst.

Chiral amines can be made by insertion of a carbene into an N-H bond using two-catalyst systems that combine a transition metal carbene-transfer catalyst and a chiral proton-transfer catalyst to enforce stereocontrol. Haem proteins can effect carbene N-H insertion, but asymmetric protonation in an active site replete with proton sources is challenging. Here we describe engineered cytochrome P450 enzymes that catalyze carbene N-H insertion to prepare biologically relevant α-amino lactones with high activity and enantioselectivity (up to 32,100 total turnovers, >99% yield and 98% e.e.). These enzymes serve as dual-function catalysts, inducing carbene transfer and promoting the subsequent proton transfer with excellent stereoselectivity in a single active site. Computational studies uncover the detailed mechanism of this new-to-nature enzymatic reaction and explain how active-site residues accelerate this transformation and provide stereocontrol.Amines are ubiquitous in bioactive molecules and functional materials 1,2 , and the development of efficient and selective methods for C-N bond construction remains one of the central themes of modern organic chemistry and biochemistry 3-5 . Among the numerous ways to construct C-N bonds, carbene insertion into N-H bonds 6-10 benefits from the high reactivity of carbene species and excellent functional group compatibility to rapidly build complex nitrogen-containing molecules. In the last several years, empowered by directed evolution, metallo-haem-dependent enzymes (cytochromes P450, cytochromes c and globins, for example) have exhibited an impressive ability to catalyze non-natural carbene-and nitrene-transfer reactions with high efficiency and selectivity. Specifically, haem proteins have been engineered to perform carbene N-H insertion reactions with catalytic efficiency far exceeding their small-molecule counterparts (up to thousands of total turnover numbers (TTN)) [11][12][13][14] . However, compared to cyclopropanation 15 , C-H insertion 16 and many other carbene transfer reactions also catalyzed by haem proteins 17,18 , N-H insertion reactions are still underdeveloped, especially with respect to high stereocontrol.In small-molecule catalysis, a common strategy for asymmetric N-H insertion is to employ a transition-metal catalyst for carbene transfer along with a separate chiral proton-transfer catalyst (PTC) for stereoinduction (Fig. 1a) 19,20 . The carbene precursor first reacts to form a metal carbene species, which can be trapped by the amine substrate through nucleophilic attack, generating an ylide intermediate. The asymmetric protonation of the ylide is then guided by a chiral PTC, such as a chiral phosphoric acid 19 or amino-thiourea 20 ; other proton sources need to be strictly avoided to ensure high asymmetric induction. Computational studies by Shaik and coworkers 21 have revealed a similar mechanism for haem protein-catalyzed N-H insertion reactions. Thus, the challenge in achieving high enantioselectivity originates from the difficulty in precisely contr...

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