Synthesis, Structure and Decarboxylative Behavior of a Nitro-coordinated Potassium Compound

A novel nitro-coordinated potassium compound [K(Htdc)(H_2O)]_n(tdc = 3-nitro-thiophene-2,5-dicarboxylate), has been synthesized and characterized. The complex with a two-dimensional(2D) layer structure contains an infinite K-O ladder-shaped chain, which is connected through carboxyl and unusual nitro-coordination of Htdc– anion. Then the 2D layers are further extended by intermolecular hydrogen-bonding to form a three-dimensional(3D) supramoleculalr network. Variable temperature powder X-ray diffractions, thermogravimetric analysis and nuclear magnetic resonance studies exhibit that the compound has a thermal-induced decarboxylative behavior.

Visible-light-induced decarboxylative alkynylation of carboxylic acids in batch and continuous flow

A green efficient photoredox-catalyzed decarboxylative alkynylation of carboxylic acids with alkynyl bromides has been developed.This broadly applicable protocol is presented whereinα-amino,aliphatic andα-oxy acids are converted into useful alkynylation products.The commercially-available organic photocatalyst 4CzIPN is used as the photocatalyst,organic base DBU is utilized as the base,and DMSO serves as solvent.This strategy features mild conditions,is metal-free,and is environmentally friendly.The batch and continuous-flow protocols described were applied to obtain a broader substrate scope of functionalization(more than 50 examples).Furthermore,we demonstrate that the use of microflow technology enhanced and intensified the reaction process,achieving significantly reduced reaction times(i.e.,10 min of residence time).

Heating-induced decarboxylative cyclization for the synthesis of 5-trifluoromethyl-1,2,4-triazoles from trifluoroacetimidohydrazides andα-oxocarboxylic acids

A simple metal and additive-free approach for the assembly of 5-trifluoromethyl-1,2,4-triazoles via only heatinginduced decarboxylative cyclization of readily available trifluoroacetimidohydrazides andα-oxocarboxylic acids has been developed.In this protocol,the rarely reported tetrahedral carboxylic acids intermediate could be in-situ generated and undergo subsequent decarboxylation to afford the target heterocycle products.

Radical Decarboxylative Cyanomethylation of Aliphatic Carboxylic Acids and Uronic Acids via Vinyl Azide Cascade Fragmentation

A direct oxidative radical decarboxylative cyanomethylation of carboxylic acids is described using 3-azido-2-methylbut-3-en-2-ol as the carbon-centered radical acceptor.The transformation is applicable to structurally diverseα-amino acids,α-oxy acids,α-keto ac-ids,pentofuranuronic acids,and hexopyranuronic acids.The mechanistic investigations suggest that a radical process is involved in the transformation.This work provides a potential approach toβ-amino acid,5-deoxy-hexofuranose,and 6-deoxy-heptose con-structs of biological relevance.

Synthesis of L-Hexopyranosyl Fluorides Enabled by Radical Decarboxylative Fluorination: Assembly of a Pentasaccharide Repeating Unit Corresponding to Extracellular Polysaccharide S-88

L-Hexoses are key components of many biologically relevant natural products and pharmaceuticals.As rare sugars,L-hexoses are not readily obtained from natural sources.Access to L-hexose building blocks from commercially available and inexpensive D-sugars is highly desirable from the viewpoints of organic synthesis and drug discovery.As demonstrated by the convenient preparation of L-glucosyl,L-galactosyl,and L-mannosyl fluorides from readily availableβ-D-C-glucosyl,β-D-C-mannosyl,andβ-D-C-galactosyl derivatives,we describe a novel and efficient approach to the demanding L-glycosyl fluorides.

Rapid formation of Csp^(3)–Csp^(3) bonds through copper-catalyzed decarboxylative Csp^(3)–H functionalization

Transition-metal-catalyzed decarboxylative and C–H functionalization strategy for the construction of Csp^(2)-Csp^(2),Csp^(2)-Csp,and Csp^(2)-Csp^(3) bonds has been extensively studied.However,research surveys of this synthetic strategy for the Csp^(3)-Csp^(3) bond forming reactions are surprisingly scarce.Herein,we present an efficient approach for the rapid formation of Csp^(3)–Csp^(3) bond through copper-catalyzed decarboxylative Csp^(3)–H functionalization.The present method should provide a useful access to C3-substituted indole scaffolds with possible biological activities.Mechanistic experiments and DFT calculations supported a dual-Cu(Ⅱ)-catalytic cycle involving rate-determining decarboxylation in an outer-sphere radical pathway and spin-crossover-promoted C–C bond formation.This strategy offers a promising synthesis method for the construction of Csp^(3)–Csp^(3) bond in the field of synthetic and pharmaceutical chemistry and extends the number of still limited copper-catalyzed decarboxylative Csp^(3)–Csp^(3) bond forming reaction.

Photocatalytic Decarboxylative Minisci Reaction Catalyzed by Palladium-Loaded Gallium Nitride

The decarboxylative Minisci reaction is a versatile tool for the direct C-H alkylation of heteroarenes,where stoichiometric amounts of oxidants or expensive,precious metal reagents are commonly used.Herein,we reported a photodriven decarboxylative Minisci reaction enabled by a gallium nitride-based heterogeneous photocatalyst under mild conditions.This method can be effectively applied to a broad substrate scope of acids,including primary,secondary,and tertiary carboxylic acids and N-heteroarenes effectively.The practicability and robustness of the approach are demonstrated for the functionalization of biologically active compounds.

Copper-Catalysed Decarboxylative Trifluoromethylation of β-Ketoacids

An efficient method for Cu-catalyzed decarboxylative trifluoromethylation offl-ketoacids to achieve a-trifluoro- methyl ketones was developed. A wide variety of synthetically useful α-trifluoromethyl ketones were obtained in modest to good yields under mild reaction conditions. The present method also exhibits good functional-group compatibility.

Photocatalytic decarboxylative coupling between α-oxocarboxylicacids and alkenes

Photocatalytic decarboxylative cross-coupling which achieves the derivatization of widespread organic acids has become a hot topic in organic synthesis.As special acids,α-oxocarboxylicacids show the great potential in running decarboxylation to construct ketone derivatives.In this article,we have developed a photocatalytic decarboxylative cross-coupling ofα-oxocarboxylic acids and olefins to the synthesis of diverse aryl ketones.Various alkenes andα-oxocarboxylicacids were compatible,generating the desired products in up to 90%yield.Preliminary mechanism studies suggest that a free radical pathway is involved in this process.

Synthesis of 3-acylindoles via decarboxylative cross-coupling reaction of free(N–H) indoles with α-oxocarboxylic acids

A convenient and general method for acylation of free （N-H） indoles via palladium-catalyzed decarboxylative cross-coupling reaction was developed. This process provided a useful method for the preparation of diverse 3-acylindoles in high yields utilizing a reaction with readily accessible reactants under mild conditions,

1D Fe3O4@CuSiO3 composites catalyzed decarboxylative A^3-coupling for propargylamine synthesis

Highly active and stable magnetic copper catalysts were successfully achieved by magnetic induced Stober method and subsequent hydrothermal reaction with copper ions in alkaline condition.The high content of Cu2+as well as the unique structures of hierarchical copper silicate in the as-prepared catalysts endowed their outstanding catalytic performance.Efficient decarboxylative A3-coupling of a-keto acid,amine and alkyne was realized with the low Fe3 O4@CuSiO3 loading.A range of propargylamines were produced in good to excellent yields under solvent-free condition.Moreover,the catalyst can be easily separated from the final organic product with an external magnet.Also,this kind of catalyst could be recycled up to six times while maintaining its activity.

Highly Stereoselective C-Glycosylation by Photocatalytic Decarboxylative Alkynylation on Anomeric Position:A Facile Access to Alkynyl C-Glycosides

The highly stereoselective synthesis of diverse medicinally valuable alkynyl C-glycosides under mild and green reaction conditions remains a great challenge.Herein,we wish to report a visible-light induced photocatalytic decarboxylative alkynylation approach.By utilizing an iridium photocatalyst in the presence of visible light,glycosyl radicals are in-situ generated via the decarboxylation of anomeric acids and efficiently coupled with a variety of ethynylbenziodoxolones(EBXs),which allows the facile synthesis of a variety of alkynyl C-glycosides in moderate to high yields and with excellent diastereoselectivity.

Photocatalytic divergent decarboxylative amination: a metal-free access to aliphatic amines and hydrazines

Nitrogen-containing motifs are widely present in natural products, bioactive molecules, and drugs. Accordingly, effective synthetic methods with high efficiency and diversity are highly desirable. Here, we present the invention of a facile, visible lightmediated decarboxylative C(sp^(3))–N bond-forming reaction by employing abundant carboxylic acids as the feedstock and a commercial diazirine as a nitrogen donor. This process is amenable to access both imines and diaziridines, as the corresponding masked amines and hydrazines, through a selectable single or double nitrogen transfer from the diazirine, respectively. This divergent approach works well in both directions with various alkyl carboxylic acids, including primary, secondary, and tertiary acids, as well as natural products and drugs, thus affording a rapid, metal-free approach to build nitrogen-containing molecule libraries with considerable structural diversity, which could thus benefit the related study in context of chemical biology and drug discovery.

Photocatalytic decarboxylative alkylations of C(sp^(3))–H and C(sp^(2))–H bonds enabled by ammonium iodide in amide solvent

A simple ammonium iodide salt in amide solvent catalyzes regioselective decarboxylative alkylation of C(sp^(3))-H bonds of Naryl glycine derivatives, of C(sp^(2))-H bond of heteroarenes, and cascade radical addition to unsaturated bond followed by intramolecular addition to arene, with a broad scope of N-hydroxyphthalimide derived redox active esters under visible light irradiation. The reactions are suggested to proceed through photoactivation of a transiently assembled chromophore from electron-deficient phthalimide moiety and iodide anion through an anion-π interaction in solvent cage followed by diffusion to generate solvated free radical species to react with C-H substrates. The simplicity, practicality, and broad substrate scope of this method highlight the synthetic power of photocatalysis through transiently assembled chromophore, and will hopefully inspire further developments of low cost photocatalysis based on various non-covalent interactions, which are prevalent in supramolecular chemistry and biosystems, for sustainable organic synthesis.

Ionic liquid-assisted preparation of hydroxyapatite and its catalytic performance for decarboxylation of itaconic acid

The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali,we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance.The results showed that the ionic liquid[Bmim]BF_(4) can affect the crystal growth of hydroxyapatite,provide fluoride ion for fluorination of hydroxyapatite,and adjust the surface acidity and basicity,morphology,textural properties,crystallinity,and composition of hydroxyapatite.The[Bmim]BF4 dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system,thus changing the degree of fluoridation of hydroxyapatite.High fluoride-ion concentration can lead to the formation of CaF_(2) and thus significantly decrease the catalytic performance of hydroxyapatite.The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis,leading to different catalytic performance.The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows:a mass ratio of[Bmim]BF4 to calcium salt=0.2:1,a hydrothermal time of 12 h,and a hydrothermal temperature of 130℃.A maximal methacrylic acid yield of 54.7%was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions(250℃ and 2 MPa of N_(2))in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.

Decarboxylative bromination of α,β-unsaturated carboxylic acids via an anodic oxidation

A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation.In this method,ammonium bromide was employed as a bromine source and the reaction features transition-metal-free,short time,and no additional supporting electrolyte.

Decarboxylative Acylation of Carboxylic Acids:Reaction Investigation and Mechanistic Study

Ketones serve as one of the most critical building blocks in organic synthesis,involving numerous functional group transformations.Herein,we rep ort an unprecedented photoredox-nickel metallap hotoredox-catalyzed decarboxylative acylation of common aliphatic acids with readily available aromatic and aliphatic thioesters.A wide range of structurally diverse asymmetrical aryl alkyl and dialkyl ketones have been constructed in yields of up to 98% with this strategy.The protocol has excellent reaction selectivity and functional group compatibility,representing a significant step forward in ketone synthesis.The one-pot decarboxylative acylation at the gram scale from two different carboxylic acids and the late-stage application for the synthesis of complex ketones shows its synthetic robustness.Both mechanistic experiments and density functional theory(DFT)calculations suggest that the decarboxylative acylation reaction operates via an underdeveloped Ni(Ⅰ)-Ni(Ⅱ)-Ni(Ⅰ)-Ni(Ⅲ)-Ni(Ⅰ)catalytic cycle.

A domino desulfitative coupling and decarboxylative coupling of 3,4-dihydropyrimidine-2-thiones with copper(Ⅰ)carboxylates

A novel and general carbon-nitrogen and carbon-carbon cross-coupling reaction between 3,4-dihydropyrimidine-2-thiones and copper（Ⅰ） carboxylates were performed in the presence of palladium acetate.The copper（Ⅰ） carboxylates act not only as desulfurative reagents but also as sources of carbon nudeophiles.A wide array of highly substituted and functionalized pyrimidines scaffolds were synthesized in good yields.

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.

Copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids under ligand-free or both ligand-and base-free conditions

An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis（pinacolato）diboron was developed, affording b-vinylboronates as the only products in high yields. Extra hydrogen sources such as methanol are not needed in this catalytic system. This reaction could be performed successfully under ligand- and base-free conditions. It demonstrated that phenylpropiolic acids can be employed as alkyne synthons in the hydroboration reaction and exhibited good reactivity and higher selectivity than terminal alkynes.