Experimental evidence for the formation mechanism of metallic catalyst-free carbon nanotubes

Our work reported that the so-called pure carbon nanotubes(CNTs)can be synthesized without metallic catalyst by chemical vapor deposition(CVD).The as-prepared CNTs have average diameter of 50 nm and length over several microns.Analysis of intermediate objects in the products indicates that their formation mechanism follows the wire-to-tube model.Besides,according to thermodynamic analysis of the driving force combing with experimental results,we find that the thermal gradient can effectively favor the formation of CNTs in our metallic catalyst-free CVD.

Oxidation of petroleum-based byproducts diformyltricyclodecanes(DFTD)with O2 under catalyst-free and ultra-low temperature

Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone(GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD.Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile,the oxidation route of DFTD–Intermediate–DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.

Catalyst-free and solvent-free method for the synthesis of quinoxalines under microwave irradiation

A facile procedure for the synthesis, of quinoxalines is being reported starting from benzil and 1,2-diaminobenzene. The reactions were carried out catalyst-free, solvent-free and under microwave irradiation conditions in high yield （84-98%） with short time （3-6 min） and environmental benign, as well as convenient operation. The structures of all the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, mass spectral data.

Solvent-free and catalyst-free method for the synthesis of 2,4,5-triarylimidazoles under microwave irradiation

A facile procedure for the synthesis of 2,4,5-lriarylimidazoles is being reported starting from benzil, aromatic aldehyde and ammonium acetate. The reactions were carried out with catalyst-free, solvent-free and under microwave irradiation conditions in high yield （80-99%） with short time （3-5 min） and environmental benign, as well as convenient operation. The structures of the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, MS, and elemental analyzer.

Perfect Solvent- and Catalyst-Free Syntheses of Imine Derivatives Using the Pressure Reduction Technique

In the field of organic syntheses, the development of environmentally friendly methods based on the concept of green chemistry has been always required. In response to this requirement, we reported solvent- and catalyst-free syntheses of imines using the pressure reduction technique as a key technology. We found that this reaction proceeded very rapidly in the initial stage, but its rate decreased with the passage of time. It was also found that the reaction of benzaldehyde with aniline had a specificity that the phase transition occurred. In this method, the desired imines could be obtained in good to excellent yields, but target compounds had to be given by purifications using organic solvents. Therefore, we tried to develop the perfect synthetic method of imine derivatives without organic or inorganic solvents. We selected two methods and took them into this investigation. One was exactly mixing (1:1, substance ratio) aldehydes and amines and the other was employing lower pressure (>0.1 mmHg, previous method: 1.0 mmHg) at the pressure reducing technique. When this improved synthetic method was performed, it was revealed that pure target imines were obtained in excellent yields without any purification.

Efficient Solvent- and Catalyst-Free Syntheses of Imine Derivatives Applying the Pressure Reduction Technique: Remarkable Change of the Reaction Rate with the Phase Transition

Because imines could be used as convenient starting materials in various fields, the development of an easy synthetic method of imine was strongly desired. In response to this demand, we thought that it would be an effective synthesis method if an aldehyde and an amine could be reacted to give an imine in good yield under solvent- and catalyst-free conditions. In fact, we tried the reaction of benzaldehyde with various amines under solvent- and catalyst-free conditions followed by removal of water that was produced in the reaction system by a vacuum pump, and desired imines could be obtained in good yields. Observation of this reaction using a nuclear magnetic resonance spectrometer revealed that the reaction rate was extremely fast at the initial stage but slowed over time. However, the reaction of benzaldehyde with aniline differed greatly, and the reaction rate dramatically improved in 47 - 48 minutes after the start of the reaction. At this time, we found that the reaction system underwent a phase transition from the liquid phase to the solid phase.

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.

Solvent- and catalyst-free synthesis of dihydropyrimidinthiones in one-pot under focused microwave irradiation conditions

Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicity, short time and the avoidance of the use of organic solvents and catalysts.

Catalyst-free electrochemical S_(N)Ar of electron-rich fluoroarenes using carboxylic acids

Herein,an electrochemically driven catalyst-free nucleophilic aromatic substitution(S_(N)Ar)of electron-rich fluoroarenes with carboxylic acids as weak nucleophiles under mild conditions was reported.A series of highly valuable ester derivatives were obtained in a direct and rapid way.This transformation features commercially available reagents and an exceptionally broad substrate scope with good functional group tolerance,using cheap and abundant electrodes and completed within a short reaction time.Gram-scale synthesis and complex biorelevant compounds ligation further highlighted the potential utility of the methodology.The mechanistic investigations and density functional theory(DFT)calculations verified the feasibility of the proposed pathway of this transformation.

Catalyst-free and atom-economical [4+3] cycloaddition of azadienes with cyclic azomethine imines for facile synthesis of 1,2,4-triazepines

A catalyst-free and atom-economical[4+3]cycloaddition of azadienes with C,N-cyclic azomethine imines has been developed,providing an efficient and environmentally benign access to 1,2,4-triazepines with high diastereoselectivities and yields.This reaction can be performed in 2-methyltetrahydrofuran under mild conditions smoothly.

Catalyst-Free Regio-and Diastereoselective Synthesis of Heterocyclic Nucleosides in the Eco-friendly Solvent 2-Methyltetrahydrofurant

An efficient and practical synthesis of heterocyclic nucleosides is developed by a catalyst-free highly regioselective and diastereose-lective[3+2]annulation of a-purine-substituted acrylates with nitrones.The reaction operates with excellent functional group toler-ance,very mild reaction conditions,and with the green,sustainable,and eco-friendly 2-methyltetrahydrofuran(2-MeTHF)as sol-vent.Compared with other reactions of electron-deficient olefin dipolarophiles with nitrones,different regioselective cycloaddition products were observed in this work.This 1,3-dipolar cycloaddition reaction gives a series of isoxazolidinyl nucleosides in good to excellent yields with promising applications in biochemistry and medicinal chemistry.

Rosin side chain type catalyst-free vitrimers with high cross-link density,mechanical strength,and thermal stability

The emergence of vitrimer,a new class of polymer materials can address the problem of recyclability,reprocess ability and recyclability of thermosetting plastics.Rosin,a natural product,is an ideal raw material for the preparation of polymers in a more sustainable way.Nevertheless,due to the huge steric hindrance caused by the hydrogenated phenanthrene ring structure,the cross-link density of materials is frequently lowered.In this study,hydrogenated rosin was adopted for preparing hydrogenated rosin side-chain type diacids,which were reacted with mixed epoxy to obtain rosin side-chain type vitrimers.It was completely characterized by differential scanning calorimetry test,thermogravimetric analysis,shape memory test and self-healing test.The prepared vitrimers exhibited good self-healing properties,excellent heat resistance(T_(d)=352℃)as well as high mechanical properties(tensile strength of 46.75 MPa).The tricyclic diterpene structure of rosin was introduced into the side chain in order to avoid the reduction of cross-link density resulting from the huge steric hindrance of the rigid tricyclic hydrophenylene skeleton.Vitrimers can undergo dynamic transesterification reaction without external catalysts due to the autocatalytic effect of tertiary amines from epoxy.Moreover,our work expanded the application field of rosin,increased the added value of rosin,and provided a novel method for preparing rosin-based vitrimers with ideal properties.

Catalyst-Free Growth of Nanographene Films on Various Substrates

We have developed a new method to grow uniform graphene films directly on various substrates, such as insulators, semiconductors, and even metals, without using any catalyst. The growth was carried out using a remote plasma enhancement chemical vapor deposition （r-PECVD） system at relatively low temperatures, enabling the deposition of graphene films up to 4-inch wafer scale. Scanning tunneling microscopy （STM） confirmed that the films are made up of nanocrystalline graphene particles of tens of nanometers in lateral size. The growth mechanism for the nanographene is analogous to that for diamond grown by PECVD methods, in spite of sp2 carbon atoms being formed in the case of graphene rather than sp3 carbon atoms as in diamond. This growth approach is simple, low-cost, and scalable, and might have potential applications in fields such as thin film resistors, gas sensors, electrode materials, and transparent conductive films.

Catalyst-Free Hydroxytrifluoromethylation of Alkenes UsingIodotrifluoromethane

The importance of CF3-containing molecules in pharmaceuticals, agrochemicals and materials intrigues the intense interest in synthetic methodology of these compounds. With a purpose to enrich trifluoromethylation methodology, we carefully examined the substrate scope of hydroxytrifluoromethylation of alkenes using iodotrifluoromethane, and the reaction provided β-trifluoromethyl alcohols in good yields under extremely mild conditions without catalysts. We found that our reaction can be applied to not only styrenes but also various aliphatic alkenes with excellent selectivity;no ketone was detected in most of our cases. Another feature of our discovery is “simple”. The reaction was carried out in air, irradiated by visible light, at room temperature and most importantly no catalyst was needed. A solution of CF3I in DMSO was used as the facile trifluoromethylating reagent, which simplified the utilization of gaseous CF3I. Based on 19F NMR spectroscopy, we observed a halogen bond between CF3I and tertiary amine in this reaction. The interaction may promote single electron transfer by the visible light irradiation.

Facile Synthesis of Functional Poly(methyltriazolylcarboxylate)s by Solvent-and Catalyst-free Butynoate-Azide Polycycloaddition

The copper-catalyzed and metal-free azide-alkyne click polymerizations have become efficient tools for polymer synthesis. However,the 1,3-dipolar polycycloadditions between internal alkynes and azides are rarely employed to construct functional polymers. Herein, the polycycloadditions of dibutynoate(1) and tetraphenylethene-containing diazides(2) were carried out at 100 °C for 12 h under solvent-and catalyst-free conditions, producing soluble poly(methyltriazolylcarboxylate)s(PMTCs) with high molecular weights in high yields. The resultant polymers were thermally stable with 5% weight loss temperatures up to 377 °C. The PMTCs showed aggregation-induced emission(AIE)properties. They could work as fluorescent sensors for detecting explosive with high sensitivity, and generate two-dimensional fluorescent photopatterns with high resolution. Furthermore, their triazolium salts could be utilized for cell-imaging applications.

Synthesis and Properties of Photodegradable Poly(furan-amine)s by a Catalyst-free Multicomponent Cyclopolymerization

A series of new photodegradable poly(furan-amine)s(PFAs) were synthesized by a one-pot, catalyst-free, multicomponent cyclopolymerization between diisocyanides, dialkylacetylene dicarboxylates, and aromatic dialdehydes. All polymerizations were conducted in toluene at 100 ℃ for 6 h without inert gas protection and furnished polymers with a satisfactory molecular weight(Mw up to32200) and yield. The PFA structure was confirmed by spectroscopic techniques, such as GPC, FTIR, and NMR, as well as by comparison with a model compound. The polymers exhibited good solubility in common organic solvents and thermal stability. All the PFAs had high refractive indices in the visible light region(400 nm to 800 nm). Moreover, the PFAs were substantially degraded by UV irradiation due to the presence of furan rings. The film thickness reduction rate could be over 90%.

Chemo-, site-selective reduction of nitroarenes under blue-light, catalyst-free conditions

The tandem reaction of photoinduced double hydrogen-atom transfer and deoxygenative transborylation for chemo-and site-selective reduction of nitroarenes into aryl amines under catalyst-free, room temperature conditions was disclosed in excellent yields. In this reaction, isopropanol(^(i)PrOH) was used as hydrogen donor and tetrahydroxydiboron [B_(2)(OH)_(4)] as deoxygenative reagent with green, cheap, and commercially available credentials. In particular, a wide range of reducible functional groups such as halogen(-Cl,-Br and even-I), alkenyl, alkynyl, aldehyde, ketone, carboxyl, and cyano are all tolerated. Moreover,the reaction preferentially reduces the nitro group at the electron-deficient site over another nitro group in the same molecule. A detailed mechanistic investigation in combination of experiments and theoretical calculations gave a reasonable explanation for the reaction pathway.

Solvent- and Catalyst-Free Direct Aldol Reactions

Aldol reaction between simple benzaldehydes and ketones successfully happened in solvent- and catalyst-free condition. The desired products were obtained in moderate yield at suitable temperature. Heat was assumed as the driving force for the reaction. This approach has obvious advantages to fully meet the requirement of the principles of green chemistry.

Catalyst-free formal[4+1]/[4+2]cyclization cascade sequence of isocyanides with two molecules of acylketene formed in situ from thermal-induced Wolff rearrangement of 2-diazo-1,3-diketones

An expedient and economic approach for constructing O,O,N-spiro compounds consisting of both a 1,3-oxazine and a furan ring through a catalyst-free formal[4+1]/[4+2]cycloaddition cascade sequence of isocyanides with two molecules of acylketene formed in situ through thermal-induced Wolff rearrangement of 2-diazo-1,3-diketones was developed.The reaction displayed good functional group tolerance and was compatible with different isocyanides and 2-diazo-1,3-diketones.Furthermore,preliminary asymmetric attempts of this reaction are made by utilizing optically pure isocyanides as inputs,and moderate diastereomeric induction was observed.

Catalyst-free Multicomponent Synthesis of β-Mercapto Diketones in Water

A simple, efficient and eco-friendly route has been developed for the synthesis of fl-mercapto diketones via a multicomponent reaction of an aldehyde, acetylacetone and thiol in water. This methodology affords a number of β-mercapto diketone derivatives in moderate to good yields.