Poly Ethylene Glycols as Efficient Media for the Synthesis of <i>β</i>-Nitro Styrenes from <i>α</i>, <i>β</i>-Unsaturated Carboxylic Acids and Metal Nitrates under Conventional and Non-Conventional Conditions

Poly ethylene glycols (PEG-200, 400, 600, 4000 and 6000) supported reactions were conducted with certain α, β-unsaturated acids in presence of metal nitrates under solvent free (solid state) and mineral acid free conditions. The reactants were ground in a mortar with a pestle for about 30 minutes. The aromatic acids underwent nitro decarboxylation and afforded β-nitro styrene derivatives in very good yield while α, β-unsaturated aliphatic carboxylic acids gave corresponding nitro derivatives. Addition of PEG accelerated rate of the reaction enormously. Reaction times substantially decreased from several hours to few minutes followed by highly significant increase in the product yield. Among the several PEGs PEG-300 has been found to be much more effective than other PEGs.

Room-Temperature Electroreductiveα-Alkylation of N-Heteroarenes with Styrenes

Despite their interesting applications,direct and diverse syntheses of aryl-fused 2-alkyl cyclic amines still remain challenging.Here,the concept of incorporating a C–C coupling process into the N-heteroaryl reduction was successfully applied to fulfill such a synthetic purpose.Due to our use of controllable electroreduction coupled with proton abstraction,we can report a room-temperature reductiveα-alkylation of the inert N-heteroarenes with abundantly available styrenes in an undivided Zn(+)/C(−)cell.This proceeds with good substrate compatibility and operational simplicity,utilizes cost-effective sacrificial Zn-anode,exhibits high selectivity,and does not need pressurized H2 gas and transition-metal catalysts.This current work offers a useful platform for direct construction of valuable aryl-fused 2-alkyl cyclic amines that are difficult to access with conventional methods.

Nickel-Catalyzed Regiodivergent Acylzincation of Styrenes with Organozincs and CO

Transition metal-catalyzed carbometallation of unsaturated hydrocarbons constitutes one of the most efficient synthetic methodologies for the construction of C—C bond.Recently,the incorporation of organometallic reagent with the CO gas as a nucleophilic acyl synthon could enable the acylmetallation reaction,which greatly increases the horizon of carbometallation chemistry.Herein,we report a nickel-catalyzed regiodivergent acylzincation of o-cyano cinnamate ester and o-cyano styrene,in which the cyano moiety intramolecularly captures zinc intermediates to trigger the tandem cyclization process.This protocol features mild conditions,broad substrate scope and excellent functional group tolerance,thus affording a diverse array of highly functionalized carbocyclic compounds.

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

We report a copper-catalyzed ligand-controlled selective carbonylative borofunctionalization ofα-substituted styrenes.This reaction provides a general and versatile procedure to synthesize a variety of synthetically usefulβ-boryl quaternary aldehydes and cyclopropyl boronate esters bearing a quaternary carbon center.With NHC(IMes=1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene)as the ligand,the carbene intermediate reacts with O-H bond of alcohol while the carbene intermediate would undergo C-H bond insertion when using phosphine ligand[1,2-bis(diphenylphospino)ethane]as the ligand.Formation of a carbene intermediate has been proposed as the key step for this transformation.

1,1-Regioselective alkenylboration of styrenes enabled by palladium catalysis

Despite the 1,2-difunctionalization reactions of styrenes have been well developed, the 1,1-regioselective addition reaction remains challenging. We disclose herein a palladium-catalyzed, highly 1,1-regioselective alkenylboration of styrenes by using alkenyl triflates and a diboron reagent as the coupling partners. A wide scope of styrenes derivatives and alkenyl triflates participate this reaction to provide the corresponding allyl boronates with high regioisomeric ratios. The success of this reaction is ascribed to the application of 1,10-phenanthroline-derivated ligand and the addition of ammonium chloride salt. Moreover, acrylate esters can also selectively afford the 1,1-alkenylboration products under the same reaction conditions.

Cobalt-Catalyzed Difunctionalization of Styrenes via Ligand Relay Catalysis

Here,we report a cobalt-catalyzed sequential dehydrogenative Heck silylation/hydroamination of styrenes with hydrosilane and diazo compound to access 1-amino-2-silyl compounds with excellent regioselectivity.This difunctionalization reaction could undergo smoothly using 1 mol%catalyst loading with good functional group tolerance.Not only di-and tri-substituted hydrosilanes,but also alkoxysilane is suitable,which does explore the scope of the family of 1-amino-2-silyl compounds.The ligand relay phenomenon between neutral tridentate NNN ligand and anionic NNN ligand is observed for the first time via absorption spectral analysis in this one-pot,two-step transformations.The primary mechanism has been proposed based on the control experiments.

Metal-free tetra-n-butylammonium bromide-mediated aerobic oxidative synthesis of β-ketosulfones from styrenes

An efficient and broadly applicable protocol for the aerobic coupling of styrenes with sulfonylhydrazides has been developed that affords P-ketosulfones bearing various functional groups in moderate to excellent yields.The preliminary experimental results support the involvement of active benzyl radical species,and a radical pathway was therefore proposed for the reaction.

Fluorescence quenching of para-substitutedstyrenes by tetramethylethylene. Correlationanalysis of the quenching coefficient KSV and thequenching rate constant k_q by the dual-parameter equation with polar and spin-delocalization substituent constants

The fluorescence quenching coefficient (Ksv) and the quenching rate constant kq of ten para-substituted styrenes (1-Ys) have been measured and correlation-analyzed by both the dual-parameter equation (Eq. 1) with (ρxσx+ρ'σ') and the single-parameter equation (Eq. 2) with ρxσx. Ex-cellent results have been obtained for the correlation of KSV against (ρxσmb+ρ'σ'JJ) or (ρxσ+ +ρ'σ'JJ). Our results suggest that, possibly, there might be no need to use excited-state substituent constant for the fluorecence quenching process of excited states of styrenes.

Et_(3)N-Catalyzed Cycloaddition Reactions ofα-(Trifluoromethyl)styrenes with 2,2,2-Trifluorodiazoethane to Access Bis(trifluoromethyl)-Substituted Pyrazolines

A novel and practical method for the synthesis of 3,5-bis(trifluoromethyl)-4,5-dihydro-1H-pyrazoles by [3+2] cycloaddition reactions of α-(trifluoromethyl)styrenes with 2,2,2-trifluorodiazoethane (CF3CHN2) has been developed. The cyclization reaction proceeds smoothly in the presence of a catalytic amount of Et_(3)N, affording a variety of bis(trifluoromethyl)-substituted 2-pyrazolines in good to excellent yields. This method also exhibits a broad substrate scope and tolerates various functional groups.

Advances in cycloaddition and hydroaddition reaction of α -(trifluoromethyl)styrenes without defluorination: An alternative approach to CF_(3) -containing compounds

α-(Trifluoromethyl)styrene and its derivatives have found wide applications in the fields of pharmaceuti-cals,agrochemicals,and advanced materials.They are also versatile trifluoromethyl-containing building blocks for the preparation of various trifluoromethyl-containing,fluorine-containing or nonfluorinated compounds.Recently,great efforts have been made to develop diverse reactions for rapidly accessing a wide range of valuable gem–difluoroalkenes and gem–difluoroalkylated compounds via defluorinative re-action or the defluorinative ipso-functionalization reaction ofα-(trifluoromethyl)styrenes,respectively.In contrast,α-(trifluoromethyl)styrenes remain notably underdeveloped with respect to their use in cycload-dition and hydroaddition reaction with retaining of three C–F bonds.This short review herein is aimed to summarize the recent progress on the cycloaddition and hydroaddition reaction including nucleophilic,radical and transition metal-catalyzed addition ofα-(trifluoromethyl)styrenes without accompanying de-fluorination.

Electrochemical Oxidative [4+2] Annulation of Different Styrenes toward the Synthesis of 1,2-Dihydronaphthalenes

A[4+2]annulation of two different styrenes to construct polysubstituted 1,2-dihydronaphthalenes was achieved.This transformation proceeded smoothly under electrochemical oxidative conditions without metal catalysts and external oxidants.A series of polysubstituted 1,2-dihydronaphthalenes were obtained with high regioselectivity and diastereoselectivity.Moreover,polysubstituted 1,2-dihydronaphthalenes were further transformed to polysubstituted 1,2,3,4-tetrahydronaphthalenes and polysubstituted naphthalenes,which show great potential in synthetic applications.

Enantioselective Arylcyanation of Styrenes via Copper-Catalyzed Radical Relay

The first copper-catalyzed enantioselective arylcyanation of styrenes has been developed using readily available anilines as aryl radical precursors under mild conditions,which enables easy access to chiral 2,3-diaryl propionitriles with moderate to good enantiose-lectivities.This operationally straightforward reaction exhibits broad substrate scope and functional group tolerance.Notably,this method has been applied to the synthesis of chiral AlEgen as well as estrogen receptor-B agonist(R)-diarylpropionitrile(DPN).

Selective Dealkenylative Functionalization of Styrenes via C-C Bond Cleavage

As a readily available feedstock,styrene with about 25 million tons of global annual production serves as an important building block and organic synthon for the synthesis of fine chemicals,polystyrene plastics,and elastomers.Thus,in the past decades,many direct transformations of this costless styrene feedstock were disclosed for the preparation of high-value chemicals,which to date,generally performed on the functionalization of styrenes through the allylic C-H bond,C(sp2)-H bond,or the C=C double bond cleavage.However,the dealkenylative functionalization of styrenes via the direct C-C single bond cleavage is so far challenging and still unknown.Herein,we report the novel and efficient C-C amination and hydroxylation reactions of styrenes for the synthesis of valuable aryl amines and phenols via the site-selective C(Ar)-C(alkenyl)single bond cleavage.This chemistry unlocks the new transformation and application of the styrene feedstock and provides an efficient protocol for the late-stage modification of substituted styrenes with the site-directed dealkenylative amination and hydroxylation.

Rhenium-Catalyzed Decarboxylative Tri-/Difluoromethylation of Styrenes with Fluorinated Carboxylic Acid-Derived Hypervalent Iodine Reagents

Summary of main observation and conclusion Herein,unprecedented rhenium-catalyzed decarboxylative oxytri-/difluoromethylation and Heck-type trifluoromethylation of styrenes have been developed by using hypervalent iodine(Ⅲ)reagents derived from cheap,stable,and easy-handling fluorinated carboxylic acids.Mechanistic studies revealed a radical decarboxylative trifluoromethylation pathway occurring in these reactions.

Styrene epoxidation catalyzed by polyoxometalate/quaternary ammonium phase transfer catalysts: The effect of cation size and catalyst deactivation mechanism

Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quaternary ammoniums bearing different cationic sizes,i.e.MTOA+(methyltrioctylammonium,[(C_(8)H_(17))_(3)CH_(3)N]+),HTMA+(hexadecyltrimethylammonium,[(C_(16)H_(33))(CH_(3))_(3)N]+) and DMDOA+(dimethyldioctadecylammonium,[(C_(18)H_(37))_(2)(CH_(3))_(2)N]+) were incorporated with polyoxometalate (POM) anions to prepare phase transfer catalysts (PTCs),which were used in the styrene epoxidations.Among them,(MTOA)_(3)PW_(4)O_(24)exhibits the best catalytic performance judged from the highest styrene conversion rate(52%) and styrene oxide selectivity (93%),during which the styrene epoxidation conditions were optimized.Meanwhile,the deactivation mechanism of this kind of PTCs was proposed firstly,i.e.in the case of low H_(2)O_(2) content,the oxidant can only be used in the styrene epoxidation,in which the catalyst can transform into stable Keggin-type POM.But when the content of H_(2)O_(2) is higher,the excess H_(2)O_(2) can reactivate the Keggin-type POM into active (PW_(4)O_(24))_(3)-anions,which can trigger the ring-opening polymerization of styrene oxide.Consequently,the catalyst is deactivated by adhered poly(styrene oxide)irreversibly,which was determined by NMR spectra.In this situation,the active moiety{PO_(4)[WO(O_(2))_(2)]_(4)}_(3)-in phase-transfer catalytic system can break into some unidentified species with low W/P ratio with the presence of epoxides.This work will be beneficial for the design of new PTCs in alkene epoxidation in fine chemical industry.

Fe-Al络合催化苯乙烯-马来酸酐交替共聚

应用Ｆｅ（ａｃａｃ）３Ａｌ（ｉＢｕ）３（ａｃａｃ＝乙酰丙酮）催化苯乙烯马来酸酐共聚，制得富于交替的白色粉末共聚物．共聚反应动力学研究表明，共聚反应与单体浓度呈一级关系，表观活化能为４８６ｋＪ／ｍｏｌ．

苯丙乳液的裂解气相色谱-质谱分析

The products of thermal desorption were generated under the temperature of 280 ℃ and were analyzed by gas chromatography-mass spectrometry with capillary column,the residual monomer styrene was no detected.The products of pyrolysis were generated under the temperature of 550 ℃ and were analyzed by chromatography-mass spectrometry,14 compounds were detected.

苯乙烯绿色氧化合成苯甲酸的机理研究

本文报道了用GC-MS跟踪了双氧水氧化苯乙烯为苯甲酸的全过程,研究结果发现4种主要物质苯乙烯、1-苯基邻二醇、羟基苯乙酮及苯甲酸含量随反应时间的变化关系,从而提出了其主要氧化机理可能为:苯乙烯首先经过环氧化反应,水解生成1-苯基邻二醇,然后1-苯基邻二醇氧化为羟基苯乙酮,羟基苯乙酮最后氧化为苯甲酸.……

Synthesis of Ln-doped MCM-41 mesoporous materials and their catalytic performance in oxidation of styrene

Using cetyl-trimethyl-ammonium bromide （CTMAB） as the template agent and tetraethylorthosilicate （TEOS） as the silica source, the MCM-41 mesoporous materials were synthesized with La or Ce incorporated in the framework under hydrothermal conditions. The structure and the state of La or Ce were investigated through the analyses of XRD, nitrogen adsorption-desorption, FT-IR, and UV-Vis. XRD and N2 adsorption-desorption results showed that Ln-MCM-41 exhibited the loss of the lattice ordering of the MCM-41 construct, and larger unit cell parameter and pore diameter than pure silica MCM-41. The FT-IR and UV-Vis results indicated the presence of isolated tetra-coordinated La or Ce ions in the framework and other Ln species dispersed highly on the Ln-MCM-41 surface simultaneously. Furthermore, their catalytic behaviors in the oxidation of styrene were studied using H2O2 as the oxidant. The La-MCM-41 catalysts exhibited high reactivity and the reactivity increased with the increase of the La content in the La-MCM-41 samples. On the contrary, Ce-MCM-41 catalysts showed low reactivity in the oxidation of styrene and the conversion of styrene decreased with the increase of the Ce content in the Ce-MCM-41 samples.