Zhenghui Liu

Reductive amination/cyclization of levulinic acid to pyrrolidones versus pyrrolidines by switching the catalyst from AlCl3 to RuCl3 under mild conditions

Herein the reductive amination/cyclization of levulinic acid using phenylsilane was presented to selectively produce pyrrolidones versus pyrrolidines under mild conditions by switching the catalyst from AlCl3 to RuCl3. Using AlCl3 as the catalyst, pyrrolidones were solely obtained at room temperature, while RuCl3 as the catalyst selectively afforded pyrrolidines in high yields at 45 °C.

Methylation of C(sp3)–H/C(sp2)–H Bonds with Methanol Catalyzed by Cobalt System

A highly efficient Co-based catalytic system, composed of a commercially available Co salt, a tetradentate phosphine ligand P(CH2CH2PPh2)3(PP3), and a base (denoted as [Co]/PP3/base), is developed for the methylation of C(sp3)-H and C(sp2)-H bonds using methanol as a methylating reagent. The Co(BF4)2·6H2O/PP3/K2CO3 catalytic system showed high catalytic activity for the methylation of C-H bonds in aryl alkyl ketones, aryl acetonitriles, and indoles, with wide substrate scope and good functional group tolerance, and methyl-substituted products were obtained in good to excellent yields at 100 °C. This cheap, readily available, and highly efficient Co-based catalytic system may have promising applications in methylation reaction using methanol.

Rhodium-Catalyzed Formylation of Aryl Halides with CO2 and H2

The reductive formylation of aryl iodides/bromides to aryl aldehydes using CO2/H2 is presented for the first time. It was realized over a catalytic system composed of RhI3 or RhI3/Pd(dppp)Cl2 (dppp = 1,3-bis(diphenyphosphino)propane) and PPh3 in the presence of Ac2O/Et3N at 100 °C, affording aromatic aldehydes in good to excellent yields, together with good functional-group tolerance and broad substrate scope. The reaction proceeds through three cascade steps, involving HCOOH formation, CO release, and formylation of aryl halides.

Cobalt-Catalyzed Synthesis of Unsymmetrically N,N-Disubstituted Formamides via Reductive Coupling of Primary Amines and Aldehydes with CO2 and H2

Herein, a novel route to synthesize unsymmetrically N, N-disubstituted formamides is reported, which is achieved via reductive coupling of primary amine and aldehyde with CO2/H2 over a cobalt-based catalytic system composed of CoF2, P(CH2CH2PPh2)3 and K2CO3. The mechanism investigation indicates that a secondary amine is formed via hydrogenation of the imine originated from aldehyde and primary amine, which further reacts with HCOOH generated from CO2 hydrogenation, resulting in the formation of NNFA finally.

Copper-catalyzed synthesis of benzanilides from lignin model substrates 2-phenoxyacetophenones under an air atmosphere

The synthesis of chemicals from biomass-derived compounds is an interesting and challenging topic. In this work, using the lignin-derived 2-phenoxyacetophenones as the feedstock we present a novel approach for the synthesis of benzanilides via the reaction of 2-phenoxyacetophenones with anilines catalyzed by CuCl2 in DMSO at 120 °C under an air atmosphere. This approach has wide scope for 2-phenoxyacetophenones and anilines, and various benzanilides accompanied by the corresponding phenols could be obtained in high yields via changing the 2-phenoxyacetophenones and anilines. The reaction mechanism study indicated that the oxidative cleavage of the C–C bond in 2-phenoxyacetophenones and the formation of a C–N bond occurred simultaneously in the reaction process, resulting in the formation of benzanilides together with phenols.

Ethanol-Mediated N-Formylation of Amines with CO2/H2 over Cobalt Catalysts

The CO2-involved synthesis of chemicals is of great significance from a green and sustainable point of view. Herein, we present an efficient Co-based catalytic system composed of a commercially available Co salt, the tetradentate phosphine ligand P-(CH2CH2PPh2)3, and a base, denoted as [Co]/PP3/base, for the synthesis of formamides via the formylation of amines with CO2/H2. It was indicated that the selectivity of products (i.e., formamide or methylamine) could be tuned to some extent via changing the solvent and the base. Using ethanol as the solvent, the Co(ClO4)2·6H2O/PP3/K2CO3 system showed high activity for the production of formamides, affording product yields of 82–95%, together with its broad substrate scope. Exploration of the reaction mechanism indicated that formamide was formed with HCOOH as the intermediate, while the methylamine byproduct was produced with HCHO as the intermediate via the hydrogenolysis of dialkylaminomethane.

Polyureas derived from CO2 and diamines: highly efficient catalysts for C–H arylation of benzene

Polyureas derived from CO2 and diamines were effective for C–H arylation of benzene in the presence of t-BuOK, producing biaryl products with various substituents in high yields up to 97%. Dual-activation of K+ and t-BuO−, and π,π-stacking interaction between the substrate and the polymer backbone may account for the superior activity.

Visible-light-driven conversion of CO2 from air to CO using an ionic liquid and a conjugated polymer

A metal-free and highly efficient catalytic system involving a task-specific ionic liquid, [P4444][p-2-O], and a pyrene-based conjugated polymer was developed for direct CO2 capture from air and its further photoreduction to CO under visible light irradiation, affording a CO production rate of 47.37 μmol g−1 h−1 with a selectivity of 98.3%.