Amine Catalyst Research Articles

Design and Synthesis of Phenylcyclopropane-based Chiral Amine Catalysts and Their Application in Asymmetric Reactions

Design and Synthesis of Phenylcyclopropane-based Chiral Amine Catalysts and Their Application in Asymmetric Reactions

Effect of Phosphorus Precursor, Reduction Temperature, and Support on the Catalytic Properties of Nickel Phosphide Catalysts in Continuous-Flow Reductive Amination of Ethyl Levulinate.

Levulinic acid and its esters (e.g., ethyl levulinate, EL) are platform chemicals derived from biomass feedstocks that can be converted to a variety of valuable compounds. Reductive amination of levulinates with primary amines and H2 over heterogeneous catalysts is an attractive method for the synthesis of N-alkyl-5-methyl-2-pyrrolidones, which are an environmentally friendly alternative to the common solvent N-methyl-2-pyrrolidone (NMP). In the present work, the catalytic properties of the different nickel phosphide catalysts supported on SiO2 and Al2O3 were studied in a reductive amination of EL with n-hexylamine to N-hexyl-5-methyl-2-pyrrolidone (HMP) in a flow reactor. The influence of the phosphorus precursor, reduction temperature, reactant ratio, and addition of acidic diluters on the catalyst performance was investigated. The Ni2P/SiO2 catalyst prepared using (NH4)2HPO4 and reduced at 600 °C provides the highest HMP yield, which reaches 98%. Although the presence of acid sites and a sufficient hydrogenating ability are important factors determining the pyrrolidone yield, the selectivity also depends on the specific features of EL adsorption on active catalytic sites.

Theoretical study on the reaction mechanism of Si2Cl6 and HCl catalyzed by amine catalysts

The study of this reaction is of great significance to the treatment of by-products in the polysilicon industry.

Cobalt single-atom catalysts for domino reductive amination and amidation of levulinic acid and related molecules to N-heterocycles

The development of single-atom-based catalysts (SACs), which bridge the traditional areas of homogeneous and heterogeneous catalysis, continues to be important for achieving organic synthesis in a more efficient and practical manner. Here, we report reusable cobalt-based SACs for the selective and general reductive amination of levulinic acid and related keto acids, which is of interest in the context of valorization of biomass. The optimal Co-SAC-based catalyst is prepared by pyrolysis (800°C) of cobalt-phenanthroline complexe on carbon and subsequent acid treatment. The resulting Co-SACs showed amazing activity compared with the corresponding Co-nanoparticles and displayed an excellent substrate scope for various reductive domino transformations including reactions of levulinic acid with nitro compounds and nitriles to produce various N-substituted pyrrolidones in good to excellent yields. Further, the synthesis of diverse isoindolinones from aromatic ketoacids and amines/nitro compounds was performed with the optimal catalyst system. • Preparation of stable and reusable Co-SACs catalysts • Reductive amination and amidation of levulinic acid and related molecules • Synthesis of >90 functionalized and structurally diverse N-heterocycles • Applicable for the preparation of bioactive molecules The effective catalytic conversion of biomass-based feedstocks to produce bulk and fine chemicals is a major goal of current chemical research. In this respect, specifically reductive aminations and amidations are interesting, too. To improve the sustainability of such processes, inexpensive, earth-abundant base metals should be employed as catalysts to replace precious metals that currently dominate in this field. Here, we show that cobalt catalysts with isolated metal sites (SACs) enable efficient domino reductive amination and amidation of levulinic acid and related molecules to give a wide array of N-heterocycles. We anticipate that these Co-catalytic systems will create more opportunities for the conversion of biomass-based feedstocks to many value-added compounds. The effective conversion of renewable resources, especially biomass-based feedstocks, to produce chemicals, fuels, and energy is of central importance. To valorize these feedstocks, the development of suitable catalysts, especially single-atom catalysts (SACs), which bridge traditional homogeneous and heterogeneous catalysis, is highly desired. In this respect, we developed Co-based SACs, which allow for the domino reductive amination and amidation of levulinic acid and related molecules to produce functionalized and structurally diverse N-heterocycles including bioactive molecules.

Co single-atom catalysts enable efficient reductive amination of biomass-derived levulinic acid

In this issue of Chem Catalysis, Gao et al. describe the first example of synthesis of cobalt single-atom catalysts (SACs) for reductive amination of levulinic acid and various ketoacids with amines, nitros, or nitriles. The cobalt SACs showed remarkable catalytic activity and excellent substrate applicability.

A General Catalyst for Buchwald-Hartwig Amination to Prepare Secondary Five-Membered Heteroaryl Amines with Breaking the Base Barrier

A General Catalyst for Buchwald-Hartwig Amination to Prepare Secondary Five-Membered Heteroaryl Amines with Breaking the Base Barrier

Natural Attapulgite Supported Nano-Ni Catalysts for the Efficient Reductive Amination of Biomass-Derived Aldehydes and Ketones

Natural Attapulgite Supported Nano-Ni Catalysts for the Efficient Reductive Amination of Biomass-Derived Aldehydes and Ketones

Design and Application of Axially Chiral Styrene-Based Thiourea-Tertiary Amine Catalysts

Design and Application of Axially Chiral Styrene-Based Thiourea-Tertiary Amine Catalysts

Catalytic asymmetric oxidative sulfenylation of β-ketocarbonyls using a chiral primary amine

Enantioselective oxidative construction of a C(sp3)–S bond has been achieved using a chiral primary amine catalyst in the presence oftert-butyl hydroperoxide and a catalytic amount of tetrabutylammonium iodide.

Aliphatic tertiary amine catalysed urethane formation - a combined experimental and theoretical study.

A kinetic and mechanistic investigation of the alcoholysis of phenyl isocyanate (PhNCO) using stoichiometric butan-1-ol (BuOH) in acetonitrile in the presence of different tertiary amine catalysts was performed. The reaction mechanisms in the absence and presence of experimentally applied catalysts were described by using the G3MP2BHandHLYP composite method. The apparent activation energies obtained from the calculations were in good agreement with the experimental data (ΔΔE = <2 kJ mol-1). Both experimental and theoretical results proved the important effect of tertiary amine catalysts on urethane formation. These results can aid in polyurethane catalyst design and development.

Sonochemistry in an organocatalytic domino reaction: an expedient multicomponent access to structurally functionalized dihydropyrano[3,2-b]pyrans, spiro-pyrano[3,2-b]pyrans, and spiro-indenoquinoxaline-pyranopyrans under ambient conditions.

A highly convenient and sustainable one-pot approach for the diversely-oriented synthesis of a variety of medicinally privileged amino-substituted 4,8-dihydropyrano[3,2-b]pyran-3-carbonitriles, and spiro[indoline-3,4′-pyrano[3,2-b]pyran]-3-carbonitrile/carboxylate derivatives on the basis of a domino three-component reaction of readily available carbonyl compounds including aryl aldehydes or isatins, active methylene compounds, and kojic acid as a Michael donor using secondary amine catalyst l-proline under ultrasound irradiation in aqueous ethanolic solution at ambient temperature has been developed. This methodology can involve the assembly of C–C, C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C, C–O, C–N bonds via a one-pot operation, and following this protocol, a series of novel amino-substituted spiro[indeno[1,2-b]quinoxaline-11,4-pyrano[3,2-b]pyran]-3-carbonitrile/carboxylates have been synthesized. The practical utility of this method was found to be very efficient for scale-up reaction and other useful transformations. The methodology provides significant advantages including mild reaction conditions, energy-efficiency, short reaction time, fast reaction, simple work-up procedure, broad functional group tolerances, utilization of reusable catalyst, green solvent system, being metal-free, ligand-free, waste-free, inexpensive, etc. Excellent chemical yields have been achieved without using column chromatography. To address the issues of green and more sustainable chemistry, several metrics including Atom Economy (AE), Reaction Mass Efficiency (RME), Atom efficiency, E-factor, Process Mass Intensity (PMI), and Carbon Efficiency (CE) have been quantified for the present methodology that indicates the greenness of the present protocol.

High performance biobased pour-in-place rigid polyurethane foams from facile prepared castor oil-based polyol: Good compatibility with pentane series blowing agent

In this paper, biobased and environmentally friendly rigid polyurethane foams (RPUF) from high hydroxyl value castor oil-based polyols have been prepared without the addition of petroleum-based polyols in the formulation. The new Biopolyol with high hydroxyl value was designed on the basis of the analysis of functionality, structure and hydroxyl value relation and synthesized directly from castor oil in a facile one-pot three-step system. A series of Biopolyols with hydroxyl values in the range of 550–650 mg KOH/g were obtained through transesterification, epoxidation, and hydrolysis. The Biopolyol chemical structure was characterized using FT-IR,1H NMR spectroscopies. The formulated blend polyol with amine catalysts and cyclopentane as a blowing agent have good cyclopentane solubility and phase separation between cyclopentane and polyol was not observed after 30 days. The foaming characteristics were evaluated and improved results were obtained. The thermal conductivity, thermal stability, compressive strength, morphology, dimensional stability, density, and foam flow of the RPUFs were characterized. The results are compared with RPUF prepared using standard commercial polyether polyols for pour-in-place RPUFs. The prepared biobased RPUFs from Biopolyol was able to reach the required satisfactory properties for the appliance industry.

Enhancing the efficiency of the ruthenium catalysts in the reductive amination without an external hydrogen source

Catalytic reductive reactions are essential for laboratory and industrial-scale organic synthesis. However, the nowadays trend is the development of new, progressively more complicated reducing systems, which hinders the application of such highly efficient approaches in practice. Another way to achieve highly active systems is enhancing the activity of the earlier developed catalysts with simple structures. Herein we demonstrated a significant increase (up to 15-fold) in the catalytic activity of ruthenium catalysts in the reductive amination after the addition of iodide to the reaction mixture. Catalyst turnover numbers up to 9000 were achieved with preparative yields of the products. The plausible reasons for this effect were formulated.

Using Solid Catalysts in Disulfide-Based Dynamic Combinatorial Solution- and Mechanochemistry.

It was shown for the first time that solid amines can act as catalysts for disulfide-based dynamic combinatorial chemistry (DCC) by ball mill grinding. The mechanochemical equilibrium for the two disulfide reactions studied was reached within 1-3 h using ten different amine catalysts. This contrasts with the weeks to months to achieve solution equilibrium for most solid amine catalysts at 2 %mol mol-1 concentration in a 2 mMolar disulfide dynamic combinatorial library in a suitable solvent. The final mechanochemical equilibrium was independent of the catalyst used but varied with other ball mill grinding factors such as the presence of traces of solvent. The different efficiencies of the amines tested were discussed.

Rational Design of Axially Chiral Styrene‐Based Organocatalysts and Their Application in Catalytic Asymmetric (2+4) Cyclizations

AbstractA new class of axially chiral styrene‐based thiourea tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements, and multiple activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo‐, diastereo‐, and enantioselective (2+4) cyclization of 2‐benzothiazolimines with homophthalic anhydrides in good yields (up to 96 %) with excellent stereoselectivities (all &gt;95:5 dr, up to 98 % ee). More importantly, theoretical calculations elucidated the important role of an axially chiral styrene moiety in controlling both the reactivity and enantioselectivity. This work not only represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, but also gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.

Rational Design of Axially Chiral Styrene-Based Organocatalysts and Their Application in Catalytic Asymmetric (2+4) Cyclizations.

A new class of axially chiral styrene-based thiourea tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements, and multiple activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo-, diastereo-, and enantioselective (2+4) cyclization of 2-benzothiazolimines with homophthalic anhydrides in good yields (up to 96 %) with excellent stereoselectivities (all >95:5 dr, up to 98 % ee). More importantly, theoretical calculations elucidated the important role of an axially chiral styrene moiety in controlling both the reactivity and enantioselectivity. This work not only represents the first design of styrene-based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2-benzothiazolimines, but also gives an in-depth understanding of axially chiral styrene-based organocatalysts.

Tetraalkyl Hydroxymethylene-bisphosphonate and Dialkyl 1-Diphenylphosphinoyl-1-hydroxy-ethylphosphonate Derivatives by the Pudovik Reaction and Their Rearranged Products.

The reaction of diethyl α-oxoethylphosphonate and diethyl oxobenzylphosphonate with diethyl phosphite, dimethyl phosphite, and diphenylphosphine oxide affords, depending on the substrates and conditions (nature and quantity of the amine catalyst, temperature, and solvent), the Pudovik adduct and/or the corresponding >P(O)–CH–O–P(O)< product formed by rearrangement. The nature of the substituent on the central carbon atom (a methyl or phenyl group) influences the inclination for the rearrangement. The asymmetric products (either adducts or rearranged species) with different P(O)Y functions (Y = RO or Ph) exhibit interesting NMR features.

Orthogonal Catalysis for an Enantioselective Domino Inverse-Electron Demand Diels-Alder/Substitution Reaction.

An enantioselective domino process for the synthesis of substituted 1,2‐dihydronaphthalenes has been developed by the combination of chiral amines and a bidentate Lewis acid in an orthogonal catalysis. This new method is based on an inverse electron‐demand Diels−Alder and a subsequent group exchange reaction. An enamine is generated in situ from an aldehyde and a chiral secondary amine catalyst that reacts with phthalazine, activated by the coordination to a bidentate Lewis acid catalyst. The absolute configuration of the product is controlled by chiral information provided by the amine. The formed ortho‐quinodimethane intermediate is then transformed via a group exchange reaction with thiols. The new method shows a broad scope and tolerates a wide range of functional groups with enantiomeric ratios up to 91 : 9. All‐in‐all, this enantioselective synthesis tool provides an easy access to complex 1,2‐dihydronaphthalenes starting from readily available phthalazine, aldehydes and thiols in a combinatorial way.

Recent advances in tertiary amine Lewis base-promoted cycloadditions of allenoates

Lewis base-catalyzed annulations of allenoates have been one of the most powerful synthetic strategies for the synthesis of various valuable cycles, especially in the preparation of biologically active natural products and pharmaceuticals. Generally, the effective Lewis bases mainly include tertiary phosphine, NHC and tertiary amine catalysts, among those catalysis, tertiary amine Lewis bases have proven to be effective catalysts for a range of synthetic transformations. In the past decades, tremendous progress involving tertiary amines-promoted cycloaddition of allenoates has been made in the chemoselective construction of valuable motifs. This review describes a comprehensive and updated summary of tertiary amine Lewis base-promoted annulation reactions of allenoates. Diverse reactivities, chemoselectivties and detailed reaction mechanisms will be highlighted in this review.

Synergistic Copper/Enamine Catalysis for the Regio-, Stereo-, and Enantioselective Intermolecular α-Addition of Aldehydes to Allenamides.

We herein describe an intermolecular enantioselective α-addition of aldehydes to allenamides using a dual copper/enamine catalytic system. Highly enantioselective addition of aldehydes was obtained thanks to secondary amine catalysts. The process was found to be highly regio-, stereo-, and enantioselective under mild conditions.