Efficient light-driven reductive amination of furfural to furfurylamine over ruthenium-cluster catalyst

Selective reductive amination of carbonyl compounds with high activity is very essential for the chemical and pharmaceutical industry,but scarcely successful paradigm was reported via efficient photocatalytic reactions.Herein,the ultrasmall Ru nanoclusters(~0.9 nm)were successfully fabricated over P25 support with positive charged Ru^(δ+)species at the interface.A new route was developed to achieve the furfural(FAL)to furfurylamine(FAM)by coupling the light-driven reductive amination and hydrogen transfer of ethanol over this type catalyst.Strikingly,the photocatalytic activity and selectivity are strongly dependent on the particle size and electronic structure of Ruthenium.The Ru^(δ+)species at the interface promote the formation of active imine intermediates;moreover,the Ru nanoclusters facilitate the separation efficiency of electrons and holes as well as accelerate the further hydrogenation of imine intermediates to product primary amines.In contrast Ru particles in larger nanometer size facilitate the formation of the furfuryl alcohol and excessive hydrogenation products.In addition,the coupling byproducts can be effectively inhibited via the construction of sub-nanocluster.This study offers a new path to produce the primary amines from biomass-derived carbonyl compounds over hybrid semiconductor/metal-clusters photocatalyst via light-driven tandem catalytic process.

Selectively reductive amination of levulinic acid with aryl amines to N-substituted aryl pyrroles

Synthesizing nitrogen(N)-containing molecules from biomass derivatives is a new strategy for production of this kind of chemicals.Herein,for the first time we present the synthesis of N-substituted aryl pyrroles via reductive amination/cyclization of levulinic acid(LA)with primary aromatic amines and hydrosilanes(e.g.,PMHS)over Cs F,and a series of N-substituted aryl pyrroles could be obtained in good to excellent yields at 120○C.The mechanism investigation indicates that the reaction proceeds in two steps:the cyclization between amine and LA occurs first to form intermediate 5-methyl-N-alkyl-1,3-dihydro-2H-pyrrolones and their isomeride(B),and then the chemo-and region-selective reduction of intermediates take place to produce the final products.This approach for synthesis of N-substituted aryl pyrroles can be performed under mild and green conditions,which may have promising applications.

ZrCl_4/Hantzsch 1,4-dihydropyridine as a new and efficient reagent combination for the direct reductive amination of aldehydes and ketones with weakly basic amines

ZrCl4/Hantzsch 1,4-dihydropyridine is a mild and highly efficient reagent combination for the direct reductive amination. Weakly basic amines such as anilines substituted by electron-withdrawing group and heteroaromatic amines can be reductively alkylated with electron rich aldehydes and ketones under mild conditions to form the secondary amines in excellent yields.

Reductive amination of aldehydes and ketones using sodium borohydride in the presence of silica chloride under solvent-free conditions

A simple and convenient procedure for the preparation of amines from aldehydes and ketones with sodium borohydride activated by silica chloride as a catalyst under solvent-free conditions is described.A variety of aliphatic and aromatic aldehydes,ketones and amines when mixed with NaBH;/silica chloride at room temperature,afforded excellent yield of the corresponding amines.

Nickel-catalyzed enantioselective reductive amination of benzylic ketones in alcohols

Asymmetric reductive amination directly converts ketones and amines to alkylamines, which are important motifs in medicines.We report that cationic nickel complexes of chiral diphosphines promote enantioselective reductive amination of benzylic ketones with both arylamines and benzhydrazide. Isopropanol was used as a safe and cheap source of hydrogen instead of formic acid. The reaction can be readily applied to a concise synthesis of diarylethylamines, a class of neuroactive substances.

A Highly Efficient Ni/Al_(2)O_(3)-LaO_(x) Catalyst for the Reductive Amination of Furfural to Furfurylamine:the Promoting Effect of La

The reductive amination of furfural to furfurylamine is an important and still challenging topic in the field of biomass conversion. In this work, we prepared a series of Ni/Al_(2)O_(3)-LaO_(x) catalysts by co-precipitation method, the role of La played in promoting the catalytic performances of reductive amination furfural was discussed based on the changes in the electronic state of Ni species, acidity, and Ni particle size. The catalytic activity and the selectivity of furfurylamine are highly dependent on the surface properties and the structure of the catalyst. The addition of La promoted the amount of strong acidic sites and the H2dissociation and spillover on the surface, thus inducing the improvement of the catalytic activity and furfurylamine selectivity. The Ni/Al_(2)O_(3)-0.5LaO_(x)catalyst with suitable acid sites gave a high yield of furfurylamine (94.9%) under mild reaction conditions. Moreover, the catalyst could be recycled five times without significant loss in activity. The Ni/Al_(2)O_(3)-LaO_(x) catalyst is of great promise in the production of amines via reductive amination reaction.

Natural attapulgite supported nano-Ni catalysts for the efficient reductive amination of biomass-derived aldehydes and ketones

The efficient synthesis of useful primary amines via reductive amination of biomass-based aldehydes and ketones over earth-abundant base metal catalysts is an attractive biomass value-adding technology yet facing lots of challenges.Herein,natural attapulgite(ATP)was applied as support for the fabrication of active Ni catalysts with different Ni loadings(5–30 wt%)by the deposition-precipitation method.The Ni/ATP-550 catalyst with 10–15 wt%Ni loadings was found to present the highest catalytic performance for the synthesis of valuable 5-amino-1-pentanol(5-AP)via reductive amination of biofurfural-derived 2-hydroxytetrahydropyran among a variety of commonly used oxide supports loaded Ni catalysts,as well as ATP supported nickel catalysts with other loadings,achieving 5-AP yield up to 94%.The intrinsic activity of the Ni/ATP catalysts was found to depend strongly on the Ni^(0) crystallite size and Ni^(0) fraction of the catalysts,which generally increased with increasing Ni^(0) crystallite size and fraction,owing probably to the hydrogenation of imine intermediate is a structure-sensitive reaction.The efficient 10Ni/ATP-550 catalyst also exhibited good activity and stability in the reductive amination of several other biomass-derived aldehydes and ketones to their corresponding primary amines with good to excellent yields(81%–99%).This work provided a clean and efficient natural ATP-supported non-noble metal nickel-based catalytic system for the reductive amination of aldehydes and ketones to synthesize high-value-added primary amines,which could be a promising candidate for the industrial production of amines.

Practical N-alkylation via homogeneous iridium-catalyzed direct reductive amination

Direct reductive amination(DRA)is one of the most efficient methods for amine synthesis.Herein we report a practical homogeneous DRA procedure utilizing iridium catalysis.Applying simple,readily available and inexpensive PPh_(3)and alike ligands along with iridium at a low loading,aldehydes and ketones reductively coupled with primary and secondary amines to efficiently form structurally and functionally diverse amine products,including a set of drugs and compounds from late-stage manipulation.The reaction conditions were exceptionally mild and additive-free,in which oxygen,moisture,polar protic groups and multiple other functional groups were tolerated.For targeted products,this methodology is especially versatile for offering multiple possible synthetic options.The 10 gram-scale synthesis further demonstrated the potential and promise of this procedure in practical amine synthesis.DFT studies reveal an“outer-sphere”H-addition pathway,in whichπ-πinteractions and H-bonding play important roles.

Catalytic reductive amination of furfural to furfurylamine on robust ultra-small Ni nanoparticles

The synthesis of primary amines via reductive amination in the presence of NH_(3)and H_(2),as a green and sustainable process,has attracted much attention.In this paper,we prepared series of Ni/SiO_(2)catalysts with deposition-precipitation and impregnation methods,and their catalytic performances on the reductive amination of a biomass derived compound of furfural to produce furfurylamine were studied.The catalytic activity and the yield were correlated to the structure and the surface properties of catalysts largely.The Ni/SiO_(2)is of high Lewis acidity and small Ni particle with numerous large Ni flat step surface showed high activity and selectivity,it afforded a reaction rate of 12.8 h^(−1)and a high yield to furfurylamine around 98%.These results are superior to the most non-noble metal catalysts reported so far.Moreover,the reaction route was examined with the unit control reactions of the intermediate.To produce furfurylamine selectively,the most suitable catalyst should have the moderate but not the highest activity in activation of hydrogen and hydrogenation in the reductive amination of furfural.This work provides some useful information for the catalytic reductive amination of aldehydes both in the design of catalyst and the reaction route.

A Fast and Highly Efficient Protocol for Reductive Amination of Aromatic Aldehydes Using NaBH4 and Isoxazole Amines in an Ionic Liquid Medium

Reductive amination of aromatic aldehydes using NaBH4 and isoxazole amines is carried out in a Bronsted acidic ionic liquid 1 -methylimidazolium tetrafluoroborate [（HMIm）BF4]. The ionic liquid plays dual roles of solvent as well as catalyst for the efficixcellent yields without any undesired side product formation. The newly synthesized compoundsent transformation of aromatic aldehydes to heterocyclic substituted amines in e （3, 6 and 7） were characterized by IR, 1H NMR and mass spectral techniques.

General Reductive Amination of Aldehydes and Ketones with Amines and Nitroaromatics under H2 by Recyclable Iridium Catalysts

Heterogeneous iridium catalysts were prepared and applied for the reductive amination of aldehydes and ketones with nitroaromatics and amines using H2. The iridium catalysts were prepared by pyrolysis of ionic liquid 1-methyl-3-cyanomethylimidazoulium chloride （[MCNI]C1） with iridium chloride （IrC13） in activated carbons. Iridium particles were well dispersed and stable in the N-doped carbon materials from [MCNI]C1 with activated carbon. The Ir@NC（600-2h） catalyst was found to be highly active and selective for the reductive amination of aldehydes and ketones using H2 and a variety of nitrobenzenes and amines were selectively converted into the corresponding secondary and tertiary amines. The Ir@NC（600-2h） catalyst can be reusable several times without evident deactivation.

Reductive Amination of Aldehydes and Ketones with Primary Amines by Using Lithium Amidoborane as Reducing Reagent

A variety of secondary amines were obtained in high isolated yields in the reductive amination of aldehydes and ketones by using lithium amidoborane as reducing agent. Compared to ammonia borane, lithium amidoborane has higher reducibility, and thus, exhibits faster reaction rate.

Iridium-Catalyzed Reductive Amination of Levulinic Acid to Pyrrolidinones under H2 in Water

The synthesis of pyrrolidinones from reductive amination of levulinic acid （LA） with primary amines is reported.Pyrrolidinones have various applications such as surfactants,pharmaceutical intermediates,dispersants,and solvents.The half-sandwich Cp＊Ir complex （Cp＊ is 1,2,3,4,5-pentamethylcyclopenta-l,3-diene） coordinated by bipyridine ligand bearing both dimethylamino and ortho-hydroxyl groups showed high catalytic activity for the reductive amination of LA.A range of primary amines,such as aromatic and benzyl amines,were readily converted to corresponding pyrrolidinones in good yields.

Efficient Synthesis of a-Amino Acid Derivatives via Phase-transfer-catalyzed Directed Reductive Amination

An efficient phase-transfer-catalyzed directed reductive amination of α-keto esters was described using simple substituted benzyl amines as nitrogen source and K2CO3 as base at room temperature, giving a series of aliphatic a-amino acid derivatives in moderate to high yields（up to 99%）. Preliminary study on this asymmetric process showed that cinchona-derived phase transfer catalyst was elTective, aflbrding the corresponding product in 13% e.e. and 40% yield.

Highly efficient synthesis of chiralβ-amino phosphine derivatives via direct asymmetric reductive amination with ammonium salts and H_(2)

A highly efficient and enantioselective method for the asymmetric reductive amination ofβ-keto phosphine de-rivatives was disclosed,and the correspondingβ-amino phosphine oxides could be obtained in high yields(up to 97%yield)and excellent enantioselectivities(up to 97%ee).Moreover,the reaction worked well on a gram scale,indicating that our protocol has potential applications in the synthesis of chiral ligands and organocatalysts.

Facile synthesis of hydrochar-supported catalysts from glucose and its catalytic activity towards the production of functional amines

Since the utilization of abundant biomass to develop advanced materials has become an utmost priority in recent years,we developed two sustainable routes(i.e.,the impregnation method and the one-pot synthesis)to prepare the hydrochar-supported catalysts and tested its catalytic performance on the reductive amination.Several techniques,such as TEM,XRD and XPS,were adopted to characterize the structural and catalytic features of samples.Results indicated that the impregnation method favors the formation of outer-sphere surface complexes with porous structure as well as well-distributed metallic nanoparticles,while the one-pot synthesis tends to form the inner-sphere surface complexes with relatively smooth appearance and amorphous metals.This difference explains the better activity of catalysts prepared by the impregnation method which can selectively convert benzaldehyde to benzylamine with an excellent yield of 93.7%under the optimal reaction conditions;in contrast,the catalyst prepared by the one-pot synthesis only exhibits a low selectivity near to zero.Furthermore,the gram-scale test catalyzed by the same catalysts exhibits a similar yield of benzylamine in comparison to its smaller scale,which is comparable to the previously reported heterogeneous noble-based catalysts.More surprisingly,the prepared catalysts can be expediently recycled by a magnetic bar and remain the satisfying catalytic activity after reusing up to five times.In conclusion,these developed catalysts enable the synthesis of functional amines with excellent selectivity and carbon balance,proving cost-effective and sustainable access to the wide application of reductive amination.

Iron/B_(2)pin_(2)catalytic system enables the generation of alkyl radicals from inert alkyl C-O bonds for amine synthesis

A method for the generation of alkyl radicals from inert alkyl C-o bonds has been developed via an iron/borane reagent/alkoxide catalytic system,which can be employed for the synthesis of amines from nitroarenes with excellent efficiency.This reductive amination features good functional group compatibility and enables the late-stage amination of bio-relevant compounds,thus providing good opportunities for applications in medicinal chemistry.Preliminary mechanistic studies reveal that the amine synthesis may be involving a Fe/Li cation-assisted single electron transfer pathway to form alkyl radicals,and the low-valent iron speciesmaybetheactive intermediates.

NiCo/Al_(2)O_(3)nanocatalysts for the synthesis of 5-amino-1-pentanol and 1,5-pentanediol from biomass-derived 2-hydroxytetrahydropyran

Al_(2)O_(3)-supported monometallic Ni,Co,and bimetallic Ni-Co nanocatalysts originated from layered double hydroxide precursors were synthesized by co-precipitation method,and used for the synthesis of useful 5-amino-1-pentanol(5-AP)and 1,5-pentanediol(1,5-PD)by reductive amination(RA)or direct hydrogenation of biofurfuralderived 2-hydroxytetrahydropyran(2-HTHP),respectively.In both reactions,the yield of the target products decreased monotonously with the increasing amounts of Co in the NiCo/Al_(2)O_(3)catalysts,owing probably to the replacement of highly reactive Ni by Co component with inferior hydrogenation activity at the low reaction temperature of 60℃.However,the incorporation of Co could improve the reducibility of the NiCo/Al_(2)O_(3)bimetallic catalysts and promote the reaction stability of the catalysts,especially for Ni_(2)Co1/Al_(2)O_(3),in both reactions with over 180 h time-on-stream.Characterization of the catalysts before and after the reaction showed that the incorporating Co could inhibit the sintering of metal particles and hinder the surface oxidation of the more reactive Ni0species,thanks to the formation of Ni-Co alloy in the bimetallic catalysts.DFT-based modeling of the reaction mechanisms is also performed,supporting the reaction pathway proposed previously and also the much higher activity of Ni in the RA of 2-HTHP as compared with Co.

Selective photosynthesis of imines from biomass-derived aldehydes over Ni/TiO_(2)

Photocatalytic reductive amination of biomass-derived aldehydes is a desirable way to selectively upgrade biomass into value-added nitrogen-containing chemicals under mild conditions.However,it is challenging to produce imines in high selectivity because of the undesirable side reactions caused by the activity of functional groups.Here,we demonstrate the highly reactive and selective production of imines from biomass derived aldehydes via the photocatalytic reductive amination,using a defective TiO_(2)supported nickel catalyst.The employment of methanol as the hydrogen donor and ammonia solution as the nitrogen source avoids the use of high-pressure H_(2)and expensive amines,rendering the current catalytic process safe,economical,and environmentally friendly.In depth investigations attribute the improved separation and transfer of photogenerated charge carriers to the presence of oxygen vacancies and decorated Ni nanoparticles,thereby accelerating the production of imines from benzaldehyde amination(conversion,95.8%;seleetivity,95.2%).Furthermore,the developed system could be easily translated to the photocatalytic conversions of various biomass derived aldehydes,which provided an example of a cost-effective and sustainable approach for the valorization of biomass derived feedstocks.

Electrochemical transformation of biomass-derived oxygenates

Replacing conventional fossil resources with renewable raw materials for chemical production and energy generation is crucial for achieving the carbon-neutral goal and alleviating the emerging energy crisis.Biomass has been considered as one of the most promising candidates for this purpose owing to its great natural abundance and inherent ability to fix CO_(2) in the form of multicarbon compounds.Particularly,biomass conversion through an electrochemical route is intriguing because of its operability near ambient conditions,flexible scalability(suitable for distributed manufacturing and even domestic use)and green generation of oxidative or reductive equivalents instead of wasteful and possibly explosive or flammable reagents.Herein,recent progress in electrochemical transformation of biomass,including hydrogenation and amination,is reviewed with the emphasis on catalysts and strategies for enhancing catalytic efficiency.The advances in mechanistic understanding using in-situ spectroscopy are also briefly discussed.Finally,recommendations for the directions for future development are also provided.