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.

Influence of Ca/P ratio on the catalytic performance of hydroxyapatite for decarboxylation of itaconic acid to methacrylic acid

Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.

Synthesis,Structure and Properties of Three-dimensional Gd(Ⅲ),Eu(Ⅲ) Coordination Polymers via in situ Decarboxylation

Two three-dimensional lanthanide（Ⅲ） coordination polymers with the formula [Ln（PYDC）（NA）（H2O）]n [Ln=Gd（1）, Eu（2）, H2PYDC=pyridine-2,5-bicarboxylic acid, HNA=nicotinic acid] have been hydrothermally synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. The NA came from in situ decarboxylation of the part of PYDC. X-ray single crystal structural analyses reveal that complexes 1 and 2 are isomorphous, they possess the 43.63 topology assembled by Gd^3＋/Eu^3＋ and two different multidentate carboxylate ligands Magnetic measurements show that antiferromagnetic coupling exists between adjacent Gd^3＋ ions in complex 1. The complex 2 exhibits the corresponding characteristic luminescence in the visible region under an excitation at 305 nm.

Biomimetic Decarboxylation of Carboxylic Acids with PhI(OAc)_2 Catalyzed by Manganese Porphyrin [Mn(TPP)OAc]

Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.

Preparation and Reactions of Pyridinium Ylids via Decarboxylation of Pyridinium Betaines

Pyridinium ylids 4 were generated as reaction intermediates from the decarboxylation of pyridinium betaines 3, which were prepared from the reactions of a-amino acid ester hydrochlorides with 2, 4, 6-triphenylpyrylium tetrafluoroborate. Protonation, addition and substitution reactions of 4 with electrophiles were studied in this paper.

The Oxidative Decarboxylation of Nitrilotriacetic Acid (NTA)——A Study of the Reaction of NTA with Cerium(Ⅳ) in HCIO_4

The reaction between Ce (IV ) and NTA was investigated titrimetrically and spectrophotometrically. Two equivalents of Ce( IV ) are reduced per mole of NTA almost instantaneously at room temperature. With increasing reaction time an ultimate of about 7 equivalents of Ce( IV) is consumed per mole of NTA at room temperature. Carbon dioxide, formaldehyde and dimethylamine are the major and readily detectable products of oxidation of NTA by Ce( IV ). The rates of the reaction in HClO4 were measured spectrophotometricaUy using the stopped flow technique. The effects of both acidity of the medium and added salts support and extend preliminary results.

How Effective Is the Single-point Energy Calculation in Investigating the Reaction Mechanisms?New Decarboxylation Mechanism of Pyrrole-2-carboxylic Acid by Full Optimization with CPCM Solvation Model

The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calculation, CPCM full optimization is better to model solvent environments to gain reasonable reaction mechanisms. The π interactions play a significant role in the decarboxylation of pyrrole-2-carboxylic acid （R）. Firstly, the a hydrogen is protonated, but all of the carbonyl hydration pathways bear relatively higher energy barriers. The carbonyl group can rove over the pyrrole ring, but it does not lead to the speciation of pyrrole and protonated carbon dioxide for the latter is an energy-rich species. The decarboxylation mechanism proposed here is that, the protonated pyrrole-2-carboxylic acid （RH） decarboxylates via direct C-C bond cleavage with the aid of a water molecule to accommodate the proton on the carbonyl group.

Synthesis,Structure and Photoluminescence of a New Cadmium(Ⅱ) Complex Involving in situ Decarboxylation

A new luminescent dinuclear cluster complex [Cd2（pzc）2（AmTAZ）（HEO）4（NO3）]·NO3 （Hpzc = pyrazine-2-carboxylic acid, AmTAZ = 3-amino-4H-1,2,4-triazole） has been prepared by the assembly of Cdn with pyrazine-2,3-dicarboxylic acid and 3-amino-lH-1,2,4-triazole-5-car- boxylic acid ligands under hydrothermal conditions, in which in situ decarboxylation of H2pzdc and HAmTZC ligands simultaneously occurred, and HEpzdc was transformed into Hpzc while HAmTZC into AmTAZ. The crystal structure is of triclinic, space group P1 with a = 7.096（2）, b = 11.140（4）, c = 14.887（5）А, α= 92.641（4）, β= 91.348（6）, γ= 96.058（6）°, V = 1168.5（7）А^3, C12H18Cd2N10O14, Mr = 751.16, Z = 2, Dc = 2.126 g/cm^3, F（000） = 730,μ=1.910 mm^-1, R = 0.0320 and wR = 0.0998 for 4549 observed reflections （I 〉 2σ（I））. The dinuclear cluster of 1 is extended into a 3D supramolecular architecture through intermolecular hydrogen bonding interactions. Complex I exhibits strong blue photoluminescence at room temperature.

Solvent- and Catalyst-Free Microwave-Assisted Decarboxylation of Malonic Acid Derivatives

It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 - 10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.

Organocatalyzed Decarboxylation of Naturally Occurring Cinnamic Acids: Potential Role in Flavoring Chemicals Production

The mechanism and the final outcome of the Knoevenagel-Doebner reaction are discussed. The condensation reaction between different hydroxy-substituted aromatic aldehydes and malonic acid is performed using piperidine as organocatalyst. The key role of the catalyst is clearly pointed out during the decarboxylation of ferulic acid, without the use of a strong decarboxylating agent, leading to a 4-vinylphenol derivative. Based on the results obtained, the studied pathway may be important in the understanding of vinylphenol production during malting and brewing of wheat and barley grains. Finally, changing the solvent of the reaction from pyridine to water in the Knoevenagel-Doebner reaction of 4-hydroxybenzaldehydes, dimerization of resulting styrene derivatives is observed. These results can be of interest also in the field of food chemistry, since cinnamic acids are frequently found in fruits and vegetables used for human consumption.

Visible-light-promoted tandem decarboxylation coupling/cyclization of N-aryl glycines with quinoxalinones: Easy access to tetrahydroimidazo [1,5-a]quinoxalin-4(5H)-ones

A visible-light-promoted formal[2+2+1]cyclization of N-aryl glycines with quinoxalin-2(1H)-ones to synthesize tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones have been developed.The protocol features operational simplicity,mild reaction conditions with blue LED light employing Ru(bpy)3Cl2.6H2O as a photoredox catalyst,a combination of O2 from air and Cu(OAc)2 as the oxidant and broad substrate applicability.

A review of anodic catalysts and their application in(non-)Kolbe electrocatalytic decarboxylation of carboxylic acids

Biomass,as the exclusive and abundant organic resources,is considered to be the promising renewable resource.Carboxylic acids are one of the many compounds that can be obtained from raw biomass.Decarboxylation of carboxylic acids into fuels and chemicals via electrochemical method at mild reaction condition has been studied for many years.The(non-)Kolbe reaction,one of the oldest organic electrochemical reactions,is the decarboxylation of carboxylic acids to produce alkanes,alcohols,esters,etc.And electrode materials influence the production of electrocatalytic decarboxylation products from carboxylic acids.Therefore,this work mainly reviews the recent advances in applications of anodic materials for(non-)Kolbe electrocatalytic decarboxylation of carboxylic acids.It discusses the reaction mechanism of(non-)Kolbe electrolytic reaction,and the electrocatalytic oxidation of carboxylic acid using different electrodes and electrolytic systems to synthesize fuels and chemicals.Also,various types of electrode catalysts,such as Pt-based catalysts,C-based catalysts,and other catalysts,are introduced in detail.Finally,the challenges and future trends of the(non-)Kolbe reaction of carboxylic acids are presented.This review found that platinum-based electrocatalysts proved to be the most promising catalysts at present.And in recent years,a variety of synthesis methods have been developed to synthesize small size and high-performance noble metal based amorphous catalysts.Another approach is to study catalysts without platinum electricity,such as Ru,Ir,Ti and carbon materials.The review is helpful in understanding and know the anodic materials and their application in(non-)Kolbe electrocatalytic decarboxylation of carboxylic acids for the readers.

Catalytic decarboxylation of fatty acid by iron-containing minerals in immature oil source rocks at low temperature

The catalytic activities of seven immature source rocks in China on fatty acid decar-boxylation for generating hydrocarbons have been evaluated by determinating the CO2 content from decarboxylation reaction of stearic acid. It has been found that the catalytic activities of immature source rocks mainly depend on the structure type of the minerals. In general,

Theoretical studies on the mechanism of the thermal decarboxylation and decarbonylation of a number of α-keto-acids

Both processes of decarboxylation and decarbonylation of a number of acids including RCOCO2H,R=H,CH3,CH2F,CF3,CH=CH2,Ph,OH have been studied by semi-empirical MO theory AMI method to verify the reaction mechanism of each process and the effect of different substituents on them.The calculated results are consistent with the experimental reports and can be summed up as follows:(1) The decarboxylation of these acids to form aldehydes and carbon dioxide is concerted and takes place through a 4-membered ring transition state in which a partial negative charge develops on the carbon of the α-carbonyl group,so that the inductive effect of some substituents is favourable for this process.(2) Their decarbonylation into carboxylic acids and carbon monoxide however is the attack of the OH on the carbon of the alkyl portion of the acid,forming a 3-membered ring transition state.(3) The activation energy of decarbonylation is lower than that of decarboxylation,since oxygen is more nucleophilic than hydrogen and also the strong OH bond need not to be broken.

Azo-coupling Decarboxylation Reaction of α-Carboxy Ketene Dithioacetals in Water-a New Route to 1,2-Diaza-1,3-butadienes

Under basic conditions, a series of 4,4-dialkylthio-l,2-diaza-l,3-butadienes were synthesized in good to excellent yields via a novel azo-coupling decarboxylation reaction by reacting a-carboxyl ketene dithioacetals with aryldiazonium salts in aqueous medium.

Supramolecular assembly of Keggin polyoxomolybdate and 2,2'-bipyridine generated in situ from a decarboxylation coupling reaction

An assembly of Keggin polyoxomolybdate and organic substrate （Hbipy）3[PM01204o] （1, bipy = 2,2＇- bipyridine） was synthesized and characterized by elemental analysis, infrared spectrum, and single- crystal X-ray analysis. The ligand bipy of compound 1 was generated by a decarboxylation coupling reaction of H2pdc （H2pdc = pyridine-2,6-dicarboxylic acid） in situ under hydrothermal reaction conditions and the control experiments illustrate that La（NO3）3 or Ce（NO3）3, which does not appear in the final structure, is necessary for the decarboxylation coupling reaction. Moreover, compound 1 displays strong photoluminescence property in the solid state at room temperature.

Instant Photochromism Caused by Radical Formation in Photocatalytic Decarboxylation of Dihydrothiazole Derivative

Main observation and conclusion A pair of new enantiomeric compounds,(R)/(S)-1,3,5-benzene-triyl-2,2',2”-tris(4,5-dihydrothiazole-4-carboxylic acid)(H3LRRR and H3LSSS)are synthesized in one step synthetic route with high yield.Instant photochromism has been investigated to elaborate the photocatalytic decarboxylation of the dihydrothiazole derivative by electron paramagnetic resonance spectroscopy(EPR),photoluminescence(PL),FT-IR,high resolution mass spectra,X-ray photoelectron spectroscopy and UV-Vis spectroscopic techniques.The results indicate that the photochromic transformation is originated from the formation of the radical during the photocatalytic decarboxylation of the 4,5-dihydrothiazole-4-carboxylic acid units.

Visible-light-promoted oxidative decarboxylation of arylacetic acids in air:Metal-free synthesis of aldehydes and ketones at room temperature

A metal-free photocatalytic oxidative decarboxylation reaction at room temperature was developed for the synthesis of aromatic aldehydes and ketones from the corresponding arylacetic acids.The reaction was realized under blue-light irradiation by adding 1 mol%of 4 CzIPN as photocatalyst and air as oxidant.This reaction represents a novel decarboxylation of a sp^3-hybridized carboxylic acids without traditional heating,additional oxidants,and metal reagents under mild conditions.

A New Cyclization/Decarboxylation Reaction of Isatins with Acyl Chlorides for the Facile Synthesis of 3-Alkenyl-oxindoles

The first cyclization/decarboxylation reaction of isatins with acyl chlorides promoted by 4-dimethylaminopyridine(DMAP)was described and a series of desired 3-alkenyl-oxindoles were obtained in good yields(up to 80%)and E/Z selectivities(up to 6.4/1).This protocol provided a new and feasible access to 3-alkenyl-oxindoles.

Catalytic decarboxylations of fatty acids in immature oil source rocks

Catalytic decarboxylations of fatty acids in immature oil source rock samples were ex-amined in this study. The rock samples were obtained from seven oil fields in China. In order to clarify the effect of each mineral matter in the rock samples, both the Fe M鰏sbauer effect and the X-ray diffraction (XRD) were used to determine the relative content of each mineral in the rock samples, and the catalytic activities of several minerals like clays, carbonates and pyrite were de-termined. The Fe M鰏sbauer effect and the XRD studies show that clays are the main mineral components in the rock samples except for the samples from Biyang and Jianghan in which the main mineral component is ankerite. The other mineral components include calcite, plagioclase, quartz, feldspar, siderite, aragonite, pyrite, analcime, pyroxene and anhydrite. The studies of the catalytic decarboxylations of fatty acids suggest that carbonates and pyrite can make much greater contributions to the catalytic activities of the rock samples than clays. It is found that the overall catalytic activities of the rock samples are well related to the relative contents and the catalytic activities of clays, carbonates and pyrite in the rock samples.