Exploration of structure and mechanism of insoluble gels formed in microwave-assisted Suzuki coupling for poly(9,9-dihexylfluorene)s

A series of poly(9,9-dihexylfluorene)s (PDHFs) have been synthesized via microwave-assisted Suzuki and Yamamoto coupling reactions. Compared with the conventional oil-bath heating (48 h, Mw 20100 g/mol by Suzuki reaction and Mw 24000 g/mol by Yamamoto reaction), microwave-assisted polymerization can yield PDHFs with higher molecular weights (Mw 37200 g/mol by Suzuki reaction and Mw 43400 g/mol by Yamamoto reaction) in shorter time (14 and 60 min). However, sometimes formation of insoluble gels was observed together with PDHF in Suzuki coupling reaction. PDHF and insoluble gels were analyzed by XPS, elemental analysis, FTIR, TGA and DSC. Experimental results demonstrated that H2O might take part in the Suzuki coupling reaction under microwave condition, which could make the cross-linking reaction occur and form gels.     

Synthesis of Chlorin—enediyne Dyads by Palladium—catalyzed Coupling Reaction

Methyl 9-ethylenedioxpyropheophorbide-d was prepared from methyl pyropheophorbide-a by protection of cyclic ketone with ethylene glycol,and oxidation with OsO4 in vinyl group at 2-position.The terminal alkyne was introduced into chlorin chromophore by Grignard reaction,and the enediyne moiety was constructed by a palladium-catalyzed coupling reaction with (Z)-chloroenynes.     

Enzymatic Synthesis of a CCK-8 Tripeptide Fragment

A process for the synthesis of CCK-8 tripeptide H-Gly-Trp-Met-OH catalyzed by immobilized enzyme was reported. Enzymes were used for the formation of peptide bonds and the removal of protecting group. Starting with phenylacetyl (PhAc) glycin, N-protected dipeptide PhAc-Gly-Trp-OMe was obtained by coupling PhAc-protected glycine carboxamidomethyl ester (OCam) with Trp-OMe catalyzed by immobilized papain in buffered ethyl acetate. Then the condensation between PhAc-Gly-Trp-OMe and Met-OEtoHC1 was carried out by immobilized α-chymotrypsin catalysis in solvent free system. Basic hydrolysis was followed getting PhAc-Gly-Trp-Met-OH. The PhAc-group was removed with penicillin G amidase and H-Gly-Trp-Met-OH was obtained in an overall yield of 43.9%. The reaction conversion of tripeptide in solvent free system was strongly affected by the system of basic salts added. The influence of the support materials used to deposit enzymes and structures of acyl donor and nucleophile on the reaction was also investigated.     

Catalytic Systems Containing p-Toluenesulfonic Acid for the Coupling Reaction of Formaldehyde and Methyl Formate

The coupling reaction of formaldehyde(FA)and methyl formate(MF)to form methyl glycolate(MG)and methyl methoxy acetate(MMAc),catalyzed by p-toluenesulfonic acid(p-TsOH)as well as assisted by different kinds of solvents or Ni-containing compounds,had been investigated.The results showed that when the reaction was carried out at 140℃,with a molar ratio of FA to MF of 0.65:1, molar fraction of p-TsOH to total feedstock of 11.0%,and reaction time of 3 h,the yield of MG and MMAc was 31.1% and 17.1%,respectively,p-TsOH catalyzed the coupling reaction by means of the synergistic catalysis of protonic acidity and soft basicity.Adding extra solvents to the reaction system was unfavorable for the reaction.The composite catalytic system consisting of p-TsOH and NiX_2(X=Cl,Br,I)exhibited a high catalytic performance for the coupling reaction,and NiX_2 acted as a promoter in the reaction,whose promotion for the catalysis increased in the following order:NiCl_2相似文献   

Stereoselective Synthesis of Novel C-Disaccharides via Suzuki Cross-Coupling Reaction

Novel β-C-disaccharides containing a three carbon linkage using exo-glycal as the precursor were prepared stereoselectively. The synthesis was achieved by the tandem reactions of the stereoselective hydroboration of exo-glycal and Suzuki cross-coupling reaction with an iodovinyl sugar, and followed by hydrogenated deprotection under the catalysis of Pd（OH）2/C.     

Mechanistic Aspects of Monomer, Polymer Formation, and Synthesis of PQ-Alt-Dialkyl-fluorene Conjugated Copolymer

Suzuki coupling reaction is widely used in the construction of conjugated polymers; however, there is still no report describing the mechanism and coupling of 9,10-phenanthrenequinone（PQ） building blocks via Suzuki reaction because PQ is sensitive to bases and light. Herein is reported the efficient Suzuki coupling of PQ with 9,10-dialkylfluorene with Na2CO3 as basic species and high molecular weight PQ-Alt-Dialkyl-Fluorene conjugated copolymer obtained in an yield of 42%. Based on the characterization data and well-accepted literature, we proposed a step-by-step mechanistic explanation for the formation of the PQ containing alternating conjugated copolymer.     

Synthesis of a novel centipede-like copolymer of styrene and methyl methacrylate

A well-defined,A2B-type,centipede-like copolymer of styrene and methyl methacrylate(PS-PS-PMMA) was synthesized by the combination of living anionic polymerization and atom transfer radical polym-erization(ATRP) . The synthetic approach involves the coupling reaction of polystyrene(PS) backbone bearing 1,1-diphenylethene(DPE) pendant groups,produced by ATRP and Wittig reaction,with living polystyryllithium(PSLi) ,and subsequent polymerization of the resulting 1,1-diphenylmethyl anions with methy methacrylate. The centipede-like copolymer was characterized by 1H NMR,IR,SEC,SLS,and DSC measurements.     

Suzuki–Miyaura cross-coupling reactions in water using in situ generated palladium(II)–phosphazane complexes

The phosphazane derivatives(L1–3) were readily obtained by reaction of different ratios of PCl3 and PhNH2. The L1–3 derivatives were found to be efficient ligands in the palladium-catalyzed Suzuki C–C coupling reactions in water. It was determined that with the use of L1–3 /Pd(OAc)2 system as a catalyst, aryl halides undergo Suzuki cross-couplings with arylboronic acids to give the desired products in moderate to excellent yields.     

Samarium diiodide induced asymmetric synthesis of γ-butyrolactone using chiral auxiliaries derived from isosorbide and isomannide

The asymmetric reductive coupling reaction of various acrylates derived from D-isosorbide and D-isomannide with acetophenone mediated by samarium diiodide to give both enan-tiomers of the optically active γ-butyrolactone was described.The best enantiomeric excess of the products was 60%.     

Rapid Microwave-promoted Base-free Suzuki Coupling Reaction of Sodium Tetraphenylborate with Hypervalent Iodonium Salts in Water

The palladium chloride-catalyzed Suzuki coupling reaction of sodium tetraphenylborate with hypervalent iodonium salts was achieved under microwave irradiation in water without base in excellent yield. A convenient and rapid method for formation of carbon-carbon bonds was afforded.     

Phase Selectively Soluble Dendritic Derivative of 4-(Dimethylamino)- pyridine: An Easily Recyclable Catalyst for Baylis-Hillman Reactions

Among the reactions in which C-C bonds are formed, the Baylis-Hillman coupling of aldehydes with α, β-unsaturated carbonylic compounds is currently attracting much interest due to the atom economy, the mild conditions and the generation of functional groups1,2. Furthermore, compared to the Heck, Suzuki and other palladium catalyzed C-C bond forming reaction3, the Baylis-Hillman reaction can be promoted by using organic bases in the complete absence of any metal4. However, almost all the …     

Peptide synthesis using pentafluorophenyl diphenylphosphate (FDP) as coupling reagent

Comparison of the reaction speed and yield with its analogues and some conventional peptide coupling reagents, pentafluorophenyl diphenylphosphate (FDP) was shown to be a more preferable "active ester" type reagent for the peptide synthesis. The synthesis of oligopeptides using FDP was achieved with high yields. The influences of several reaction parameters such as solvent, base, additive and temperature on the coupling reaction were studied using HPLC method. The degree of racemization with FDP determined by HPLC or Young test was shown to be lower than that of DCCI. Octapeptide Gly-Cys(Bzl)-Ser-Gly-Lys-Leu-Ile-Cys(Bzl)-OH, corresponding to the amino acid sequence of gp41 of HIV-1, was successfully synthesized by 5+3 approach using FDP with high yield.     

Study on the Total Synthesis of Et 743 and its Analogues： Synthesis of a Tricyclic Intermediate and its 11-Epimer

The tricyclic compound 1, a key intermediate of the pentacyclic core of Et 743 and its analogues, was synthesized. Its 11-epimer was found as the product of racemization when BOP was used as the coupling agen4 but not when BOP-Cl used in the same reaction. The stereochemistry of both isomers was confirmed on basis of the ^1H NMR and NOE-difference spectra.     

Trace Ir(Ⅲ) complex enhanced electrochemiluminescence of AIE-active Pdots in aqueous media

Trace Ir(Ⅲ) complex enhanced aggregation-induced electrochemiluminescence(AIECL) of poly-tetraphenylethene(p TPE) in aqueous media was investigated for the first time. The poly-TPE end-capped by Ir(Ⅲ) complex(Ir@p TPE) and its corresponding model polymer poly-TPE(Ph@pTPE) could be synthesized by Suzuki coupling polymerization reaction of 1,2-bis(4-bromophenyl)-1,2-diphenylethene(M-1) with 1,2-diphenyl-1,2-bis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)ethene(M-2) and the continuous Suzuki coupling end-capped reaction of poly-TPE-pinacol boronate with(pq)2 Ir(pico)Br and bromobenzene, respectively. Subsequently, the corresponding Ir@p TPE Pdots and Ph@p TPE Pdots encapsulated with poly(styrene-co-maleicanhydride)(PSMA) could be obtained by nanoprecipitation method. Compared with Ph@p TPE Pdots, the Ir@p TPE Pdots with a trace amount of Ir(Ⅲ) complex(1.34‰ of Ir(Ⅲ) content, wt) could exhibit 9.9-fold enhancement of the electrochemiluminescence(ECL) signal for visual emission. This work provided a novel strategy on designing highly efficient ECL materials based on trace Ir(Ⅲ)-end capping AIE-active polymer dots.     

Preparation of 6,6′—Bisperfluoroalkylated BINOLs and Their Application in Asymmetric Alkylation of Benzaldehyde

6，6′-Bis(1H,1H,2H,2H-perfluorooctyl)-BINOL and 6,6′-bis(1H,1H,2H,2H-perfluorodecyl)-BINOL were synthesized through Suzuki coupling reaction and used in fluorous biphase asymmetric alkylation of benzldehyde,Good enantioselectivity was obtained and the catalysts could be recovered by liquid-liq-uid extraction.     

Suzuki reaction of bromoallenes with arylboronic acids using an air-stable palladium complex Pd(Ph_2PCH_2CO_2)_2 as a precatalyst

<正>Suzuki reaction of bromoallenes with arylboronic acids was successfully performed by using an air-stable hemilabile P-O coordinated cyclopalladated complex Pd(Ph_2PCH_2CO_2)_2 as a precatalyst,and the corresponding coupling products were obtained in satisfactory to excellent yields.All products are unknown compounds which were characterized by ~1H NMR,~(13)C NMR,IR,and HRMS.     

NOVEL HYPERBRANCHED POLY（PHENYLENE OXIDE）S WITH PHENOLIC TERMINAL GROUPS： EFFECTS OF REACTION TIME AND CORE MOLECULES ON THE MOLECULAR WEIGHT AND POLYDISPERSITY

A novel hyperbranched poly（phenylene oxide） （HPPO） with phenolic terminal groups was prepared from 4-bromo-4＇,4＂-dihydroxytriphenylmethane as AB2 monomer in dimethylsulfoxide （DMSO） via a modified Ullmann reaction. The molecular weight and polydispersity （PD） of the resulting polymers increased with increasing reaction time. In the presence of core molecules （bisphenol A and 1,3,5-trihydroxybenzene）, which have the similar molecular backbones to the reactive monomer, the molecular weight could be controlled by varying the core-to-monomer ratio. Incorporation of a very small amount of core molecules could lead to a higher molecular weight as compared with that without the addition of core molecules. However, when the core content reached certain extent, the molecular weight would decrease with the further increase in the core content. A new similar behavior of control over the PD was also obtained. The resulting polymers were characterized by ^1H-NMR, ^13C-NMR, FT-IR, and GPC.     

Cyclopalladated Ferrocenylimine: Highly Active Catalyst for the Suzuki Reaction of Aryliodides with Phenylboronic Acid

Transition-metal catalyzed reaction represents an extremely versatile method in organic synthesis. [1] Searching for highly efficient catalysts has been the aim of organic chemists. Palladium catalyzed coupling of aryl halides with arylboronic acids, Suzuki reaction, is one of the most powerful methods for carbon-carbon bond formation. [2] Here we report the high efficiency of cyclopalladated ferrocenylimine 1 for the Suzuki coupling reaction of aryl iodides with phenylboronic acid. Excellent yields and high turnover numbers were obtained under optimized conditions after repeated uses (Schemes 1, 2).     

Polystyrene-supported Phenol/DMAP： an Efficient Binary Catalyst System for CO2 Fixation to Give Cyclic Carbonates

Polystyrene-supported phenol （PS-PhOH） was successfully synthesized by alkylation reaction of phenol with 2% DVB cross-linked chloromethylated polystyrene and characterized by IR spectra and elemental analysis. In conjunction with an organic base such as DMAP, DBU, triethylamine （Et3N）, diethylamine （Et2NH） or pyridine, the PS-PhOH could effectively catalyze the coupling reaction of carbon dioxide with epoxides to give cyclic carbonates in high yield and selectivity under mild conditions. The binary catalyst system of the PS-PhOH/DMAP was found to be the most active. The influence of reaction temperature, carbon dioxide pressure and reaction time on the yield of product was carefully investigated. The PS-PhOH could be recycled by simple filtration for at least up to ten times without loss of catalytic activity.     

Theoretical and Experimental Study on Reaction Coupling： Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

Dehydrogenation of ethylbenzene (EB) to styrene (ST) in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift (RWGS), was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.