Selective synthesis of formamides, 1,2-bis(N-heterocyclic)ethanes and methylamines from cyclic amines and CO2/H2 catalyzed by an ionic liquid-Pd/C system

Aerobic Oxidative Synthesis of Formamides from Amines and Bioderived Formyl Surrogates

Herein we present a new strategy for the oxidative synthesis of formamides from various types of amines and bioderived formyl sources (DHA, GLA and GLCA) and molecular oxygen (O2) as oxidant on g-C3N4 supported Cu catalysts. Combined characterization data from EPR, XAFS, XRD and XPS revealed the formation of single CuN4 sites on supported Cuphen/C3N4 catalysts. EPR spin trapping experiments disclosed ⋅OOH radicals as reactive oxygen species and ⋅NR1R2 radicals being responsible for the initial C-C bond cleavage. Control experiments and DFT calculations showed that the successive C-C bond cleavage in DHA proceeds via a reaction mechanism co-mediated by ⋅NR1R2 and ⋅OOH radicals based on the well-equilibrated CuII and CuI cycle. Our catalyst has much higher activity (TOF) than those based on noble metals.

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Solvent-free continuous flow hydrogenation of N-methylpyrrolidone to N-methylpyrrolidine catalyzed by bimetallic Pt/V on HAP

The continuous flow hydrogenation of N-methylpyrrolidone which catalyzed by Pt/V/HAP (Pt/V molar ratio = 1 : 0.5) was achieved running for 100 h with solvent-free, and the N-methylpyrrolidine yield was above 85.21%.

Ionic-Liquid-Catalyzed Approaches under Metal-Free Conditions

ConspectusMetal-free catalysis is a promising protocol to access chemicals without metal contamination. Ionic liquids (ILs) that are entirely composed of organic cations and inorganic/organic anions have emerged as promising alternatives to molecular solvents and metal catalysts due to their unique properties such as structural tunability, the coexistence of multiple interactions among ions (e.g., electrostatic interaction, hydrogen bonding, van de Waals forces, acid/base interactions, hydrophilic/hydrophobic interactions, etc.), unique affinity for a wide range of chemicals, good chemical and thermal stability, and quite low volatility. ILs have shown potential applications in various chemical processes.In this Account, we systematically described our most recent work on IL-catalyzed approaches under metal-free conditions. The first section presents the IL-catalyzed strategies toward the transformation of CO2 to value-added chemicals, focusing on the CO2-reactive IL-catalyzed CO2 transformation to various heterocycles and the IL-catalyzed reductive transformation of CO2 to chemicals. In these approaches, we designed task-specific ILs that are able to chemically capture and activate CO2 via forming anion-based carbonate/carbamate or cation-based carboxylate/carbamate intermediates, thus further accomplishing its transformation to a series of heterocycles including quinazoline-2,4(1H,3H)-diones, cyclic carbonates, 2-oxazolidinones, oxazolones, and benzimidazolones under metal-free conditions. For the IL-catalyzed approaches to reducing CO2 with hydrosilanes to chemicals, we employed ILs capable of activating the Si-H bond in hydrosilanes and the N-H bond in amine substrates via H-bonding, thus achieving the reductive transformation of CO2 to formamides, benzimidazoles, and benzothiazoles via cooperative catalysis. The second section describes our finding on the IL-catalyzed hydration of the C≡C bond in propargylic alcohols. Azolate anion-based ILs that can chemically capture CO2 via the formation of carbamates could serve as robust nucleophiles to attack the C≡C bond in propargylic alcohols and then efficiently catalyze the hydration of propargylic alcohols to produce α-hydroxy ketones with the assistance of atmospheric CO2 gas under metal-free conditions. The third section unveils the cooperative catalysis strategy of hydrogen bond donors and acceptors of ILs for chemical reactions. In the hydrogen-bonding catalysis protocols, cations of the ILs act as H-bond donors and anions, as acceptors, forming H-bonds with the reactant molecules, respectively, in opposite ways, which can cooperatively catalyze the ring-closing C-O/C-O bond metathesis reactions of aliphatic diethers to O-heterocycles, the dehydrative etherification of alcohols to ethers, and direct oxidative esterification of alcohols to esters. We believe that these IL-catalyzed metal-free processes and strategies display promising practical applications, and their commercialization would bring great benefits to the production of the as-afforded value-added chemicals.

Steam reforming of formaldehyde for generating hydrogen and coproducing carbon nanotubes for enhanced photosynthesis

NiO/MoO₃ exhibits high catalytic activity, and the carbon deposition can be used as nanopesticide.