Na-MnO_(x) catalyzed aerobic oxidative cleavage of biomass-derived 1,2-diols to synthesis medium-chain furanic chemicals

Medium-chain furanic chemicals have outstanding practical potential,especially in the application of pharmaceuticals and polymers.Herein,we describe an eco-friendly and efficient heterogeneous sodium-doped porous sodium manganese oxide catalyst(Na-MnO_(x)) for oxidative cleavage of furanic 1,2-diols into medium-chain furanic aldehyde compounds.Subsequently,various high value-added chemicals(diacids and esters,diols,hydroxy acids,acrylics) were synthesized based on the widely applicable and highly selective catalytic approaches.The Na-MnO_(x) was prepared by the coprecipitation method and characterized by XRD,SEM,XPS and FT-IR,and TGA.XPS revealed that Mn species existed in the mixed oxidation states Mn~Ⅱ,Mn~Ⅲ and Mn~Ⅳ.When NaOH concentration up to 1.8 mol L^(-1) during the preparation process of the catalyst,the ratio of Mn^(4+) in the catalyst was the highest,and the yield of product(Furan-2-acrolein) in the model reaction is also optimal.Overall,this protocol developed a novel and general route for the preparation of medium-chain furanic compounds utilizing cellulose-derived platform molecules.

Synthesis of dihydrocapsaicin and dihydrocapsiate exclusively from lignocellulosic platform chemicals

Biorefinery is pivotal to the sustainability of modern chemical industry.However,since biomass is oxygen-enriched,new and green chemical strategies are required for expanding the biomass derived chemical space.In this work,synthesis of natural products dihydrocapsaicin and dihydrocapsiate was achieved exclusively from lignocellulosic platform chemicals.Natural products dihydrocapsaicin and dihydrocapsiate were synthesized exclusively from lignocellulosic platform chemicals,using furfural(from hemicellulose)and methyl isopropyl ketone(from cellulose)through aldol condensation-hydrolysis-hydrodeoxygenation to synthesize 8-methylnonanoic acid and then combined with vanillin derivates(from lignin).This synthesis demonstrates the feasibility of constructing natural products entirely from renewable biomass platform through green processes.The utilization of inherent functional groups of biomass demonstrates their potential to open up chemical space.

Cobalt-catalyzed reductive alkynylation to construct C(sp)-C(sp^(3))and C(sp)-C(sp^(2))bonds

Transition-metal-catalyzed cross-electrophile coupling has emerged as a reliable method for constructing carbon–carbon bonds.Herein,we report a general method,cobalt-catalyzed reductive alkynylation,to construct C(sp)-C(sp^(3))and C(sp)-C(sp^(2))bonds.This presented reaction has a broad substrate scope,enabling the efficient cross-electrophile coupling between alkynyl bromides with alkyl halides and aryl or alkenyl(pseudo)halides.This presented reaction is conducted under mild conditions,tolerating many functional groups,thus suitable for the modification and synthesis of biologically active molecules.

Thermal-reductive transformations of carbon dioxide catalyzed by small molecules using earth-abundant elements

In the present review, we summarize the progress for thermal reductive transformations of CO2 catalyzed by small homogeneous catalysts using earth-abundant elements. Three main types of transformations categorized by the use of different reductants(hydrogen, hydrosilanes, and boranes), in which no C–C bond formation is involved, are surveyed.

Recent advances in catalytic production of sugar alcohols and their applications

Conversion of non-edible biomass into fuels and value-added chemicals has achieved great attention to cope the world's energy requirements. Lignocellulose based sugar alcohols such as sorbitol, mannitol, xylitol, and erythritol can be potentially used as emerging fuels and chemicals. These sugar alcohols can be converted into widely used products(e.g. polymer synthesis, food and pharmaceuticals industry). The heterogeneous catalytic production of sugar alcohols from renewable biomass provides a safe and sustainable approach. Hydrolysis, coupled with hydrogenation and hydrogenolysis has been proved to be more effective strategy for sugar alcohols production from biomass. This review summarizes the recent advances in biomass upgrading reactions for the production of sugar alcohols and their comprehensive applications.

Recent advances in nickel-catalyzed reductive hydroalkylation and hydroarylation of electronically unbiased alkenes

The use of simple and easily available feedstock to quickly and efficiently obtain compounds with complex molecular structures through the transition-metal-catalyzed construction of C(sp3)–C bonds has important significance.As traditional C(sp3)–C coupling reagents,alkylmetallic reagents often have limitations such as air and moisture sensitivity and difficulties in storage.Nickel-catalyzed reductive olefin hydrocarbonation reactions use alkenes to replace organometallic reagents,reduce the synthesis steps,improve the functional group compatibility,and expand the substrate scope.This minireview discusses important progress in the hydroalkylation and hydroarylation of electronically unbiased alkenes in recent years and describes the key mechanism and applications.

Efficient Decarboxylative/Defluorinative Alkylation for the Synthesis of gem-Difluoroalkenes through an SN2’-Type Route

An efficient decarboxylative/defluorinative alkylation for synthesizing gem-difluoroalkenes is described,providing a general method for installation of the challenging alkyl fragments containing a-electron-withdrawing groups into a-trifluoromethyl alkenes.Mechanistic studies suggest that this process involves an SN2,-type synthetic route in the absence of transition-metal catalysts or photocatalysis.Moreover,this protocol can easily be scaled up,and successfully applied to the modification of biologically active molecules,thus complementing methodologies that give access to structurally versatile gem-difluoroalkenes.

Selectively Chemocatalytic Conversion of Fructose to 1,2-Propylene Glycol over Ru-WOx/Hydroxyapatite Catalyst

The conversion of fructose to 1,2-propylene glycol(PG)is an important process from cellulosic biomass to high-value added chemicals.Herein,Ru-WOx/hydroxyapatite(HAP)catalyst was employed for this reaction and reached up to 91.3%yield of PG at 180℃,1 MPa initial hydrogen for 8 h in water.On this catalyst,Ru and WOx were highly dispersed on HAP support and they interacted with each other to form a special catalytic center.The lack of isolated Ru or RuW alloy site led to a moderate activity for hydrogenolysis and hindered the further conversion of PG to propanol.The weak basic HAP support efficiently prevented the humin formation.This precisely controlled catalyst has potential in green PG production.

Products and production routes for the catalytic conversion of seed oil into fuel and chemicals: a comprehensive review

With the depletion of fossil resources, there is a need to find alternative resources of fuels and chemicals. The use of renewable feedstock such as those from seed oil processing is one of the best available resources that have come to the fore-front recently. This paper critically analyzes and highlights major factors in the biodiesel industry, such as seeds oil composition, production methods, properties of biodiesel, problems and potential solutions of using vegetable seed oil, the composition, quality and effective utilization of crude glycerol, the catalytic conversion of glycerol into possible fuels and chemicals.

Iron-catalyzed selective oxidation of 5-hydroxylmethylfurfural in air:A facile synthesis of 2,5-diformylfuran at room temperature

An iron（Ⅲ）-catalyzed selective oxidation of 5-HMF to 2,5-DFF in air at room temperature was developed.This approach gives 2,5-DFF with good selectivity and yields. Additionally, a two-step process was developed for the oxidation of 2,5-DFF to 2,5-FDCA at remarkably high substrate concentrations. This work demonstrates unequivocally the great potential of iron as a cheap and earth-abundant catalyst for the development of new protocols for the conversion of biomass to value-added chemicals.

NiH-Catalyzed Reductive Hydrocarbonation of Enol Esters and Ethers

Chiral dialkyl carbinols and their derivatives are significant synthetic building blocks in organic chemistry and related fields.The development of convenient and efficient methods to access these compounds has long been an important endeavor.Herein,we report a NiH-catalyzed reductive hydroalkylation and hydroarylation of enol esters and ethers.α-Oxoalkyl organonickel species were generated in situ in a catalytic mode and then participated in cross-coupling with alkyl or aryl halides.This approach enabled C(sp^(3))–C(sp^(3))and C(sp^(3))–C(sp^(2))bond formation under mild reductive conditions with simple operations,thereby boosting a broad substrate scope and good functional compatibility.Esters of enantioenriched dialkyl carbinols were accessed in a catalytic asymmetric version.Mechanistic studies demonstrated that this reaction proceeded through a syn-addition of Ni–H intermediate to an enol ester with high regio-and enantioselectivity.

Transition-metal-catalyzed C-H functionalization for late-stage modification of peptides and proteins

Late-stage modification of peptides and proteins meets the increasing demand in biochemical and pharmaceutical communities. These modification strategies could provide functionalized nonproteinogenic analogues with enhanced biological activities or improved therapeutic capabilities compared to their natural counterparts. Recent years, transition-metal-promoted functionalization of ubiquitous C-H bonds has been emerged as a powerful and tunable tool in this area, both for backbone diversifications and labeling of specific moieties. These reactions were flexible and expedient in both academic and industrial laboratories, especially considering their atom and step-economy, good functional group compatibility, accurate site selectivity. This review surveys the progress achieved in the late-stage modification of peptides and proteins utilizing transition-metal-catalyzed C-H functionalization with C-C and C-X(F, Cl, O, N, B, etc.) bonds formation.

A mechanistic study on the regioselective Ni-catalyzed methylation–alkenylation of alkyne with AlMe3 and allylic alcohol

The recently reported Ni-catalyzed methylation–allylation of alkynes with allylic alcohols and AlMe3 reagents delivers valuable tetrasubstituted alkene units in a highly regioselective fashion.Motivated by the experimental significance and the mechanistic ambiguity(e.g.the details of C–O bond activation,the function of the Lewis acid AlMe3,etc.),we conducted a detailed mechanistic study using density functional theory(DFT)calculations.The reaction was found to occur via the C–O bond activation of allylic alcohol,allylation of alkyne,transmetalation,reductive elimination and catalyst regeneration steps.AlMe3 could easily react with the allylic alcohol to form a cyclodialuminoxane species bearing two groups of Lewis acid–base interactions.In this regard,the C(allyl)–O bond is remarkably activated,resulting in a relatively facile C–O activation(compared to the typical Lewis-acid mediated reactions).In addition,the Al–Me interaction is a double-edged sword to the methylation step:the cyclodialuminoxane group functions as the methyl resource,while the full dissociation of the Al–Me interaction(via a cis-to-trans isomerization)is a requisite to fully release the methyl group.In this context,the“Me-relay”pathway involving the[Ni]–Me intermediate is found to be more plausible than all other mechanistic possibilities(such as the typical concerted Me-transfer mechanism in previous studies).

Recent Advances in Cobalt-Catalyzed Regio-or Stereoselective Hydrofunctionalization of Alkenes and Alkynes

Hydrofunctionalization of alkenes and alkynes is increasingly important in preparing and modifying carbon-centered organic molecules such as pharmaceuticals,agrochemicals,andmaterial precursors.The development of transition-metal-catalysts has revolutionized the hydrofunctionalization of unsaturated hydrocarbons,greatly improving the synthetic efficiency and selectivity of these reactions.In recent years,notable progress has been achieved in low-cost metal-catalyzed alkene and alkyne hydrofunctionalization reactions following the utilization of traditional precious metal catalysts,including palladium,platinum,and rhodium.Earth-abundant cobalt catalysts,which are low in toxicity and exhibit unique reactivity and selectivity,are widely implemented in academic and industrial research.In this review,we highlight recent examples of cobalt-catalyzed hydrofunctionalization of alkenes and alkynes to provide an overview of hydrofunctionalization methods,particularly hydroalkylation reactions.Hydroalkylation reactions greatly expand the scope and utility of cobalt-catalyzed couplings of carbon—carbon bonds.We also highlight the mechanistic considerations and selective determinants involved.We hope our discussion will be informative for future developments in cobalt catalysis and hydrofunctionalization reactions.

Mechanistic insights into the rhodium-catalyzed aryl C-H carboxylation

The recently reported Rh(Ⅱ)-catalyzed direct C-H bond activation and lactonization of 2-arylphenols uncovers an attractive strategy to prepare coumarin derivatives with novel chemoselectivity.Motivated by the mechanistic ambiguity(on the origin of the chemoselectivity and the details for lactonization etc.),we conducted a detailed mechanistic study for the rhodium-catalyzed lactonization of 2-arylphenols with density functional theory(DFT)calculations.The results suggest that the reaction occurs via the coordination exchange,C-H bond activation,carboxylation,protonation and lactonization steps.The rate-determining step is the carboxylation,in which CO_(2) favorably inserts into the Rh-C bond(instead of the more nucleophilic Rh-O bond).The protonation step after carboxylation is critical,which makes the subsequent CO_(2)-assisted lactonization feasible.Interestingly,the corresponding pK_(a) value of the base can reasonably predict the reaction energy barrier of the C-H bond activation step.The calculations will provide insights and suggestions for developing and advancing the subsequent C-H bond activation carboxylation reaction.

Photoinduced Dehalocyclization to Access Oxindoles Using Formate as a Reductant

Herein,we report an efficient and practical protocol for the photoinduced dehalocyclization of ortho-halophenylacrylamides with formate by the engagement of a CO_(2) radical anion to access substituted oxindoles.This method proceeds smoothly under mild conditions and exhibits a wide range of substrate as well as remarkable functional group compatibility.