在催化体系可回收和无配体条件下溴化四丁基铵中钯催化卤代芳烃与芳基硼酸的Suzuki-Miyaura交叉偶联反应

我们发展一种在催化体系可回收和无配体条件下溴化四丁基铵（TBAB）中钯催化卤代芳烃与芳基硼酸的Suzuki-Miyaura交叉偶联反应方法。我们发现水的量对反应有很大的影响。当水的用量为1 %（质量比）时,反应的结果最好。在3 mol%的醋酸钯和1.5 g的TBAB（含1%的水）,一系列卤代芳烃与芳基硼酸的顺利地发生Suzuki-Miyaura交叉偶联反应,得到中等及良好的产率。而且在溴代芳烃和活泼的氯代芳烃的交叉反应中,Pd(OAc)2/TBAB催化体系可以回收重复使用多次,并且催化活性基本不变。     

A comparison of homogeneous and biphasic hydrogenation systems of macrocyclic lactones with in situ formed rhodium complexes

Homogeneous and biphasic hydrogenation of avermectins catalyzed by rhodium complexes in situ formed from [RhCl(COD)]₂ and triphenylphosphine or sulphonated arylphosphines, respectively, was studied under mild reaction conditions. Effects of adding TBAB and bis-QACs as phase transfer agents, Tween? 80 as non-ionic surfactant, β-cyclodextrin as inverse phase-transfer agent, and triphenylphosphine as co-ligand, are reported for the biphasic system.     

Comparative Study of Catalytic Potential of TBAB,BTEAC, and CTAB in One-Pot Synthesis of 1,4-Dihydropyridines Under Aqueous Medium

Convenient and straightforward tetrabutylammonium bromide (TBAB), benzyltrienthylammonium chloride (BTEAC), and cetyltrimethylammonium bromide (CTAB) catalyzed synthesis of 1,4-dihydropyridines (1,4-DHPs) in water was established for the first time. The catalytic potential of phase-transfer catalysts (PTCs) in three different concentrations was envisioned. Aryl aldehydes and hetero aryl aldehydes afforded good yields of 1,4-DHPs in TBAB and BTEAC reactions. In particular, furfuraldehyde and thienyl-2-carbaldehyde produced excellent yields. Isolation of the products through nonchromatographic methods, good to excellent yields, and benign reaction conditions are the major advantages of this protocol.     

水相中Pd/C催化的杂环芳卤的还原偶联反应研究

在H₂O-alcohol体系中通过Pd/C催化的还原偶联反应由杂环芳卤高收率的得到了二芳基化合物. 该方法操作简单, 环境友好, Pd/C可重复使用, 无需相转移催化剂也能得到较高收率. 讨论了醇、碱的种类和用量以及不同底物对反应收率的影响.     

Syntheses of indolo[3,2,1-d,e]phenanthridines and isochromeno[3,4-a] carbazoles: palladium catalyzed intramolecular arylation via C-H functionalization

A new synthetic route has been developed for the preparation of indolo[3,2,1-d,e]phenanthridines and isochromeno[3,4-a]carbazoles via palladium catalyzed intramolecular biaryl coupling reactions. The coupling reactions proceeded smoothly and in high yields under ligand-free conditions with the catalytic system Pd(OAc)₂/Cs₂CO₃/TBAB. Under optimized reaction conditions no halogen-reduced products were observed.     

Phase-transfer agents as catalysts for a nucleophilic substitution reaction in microemulsions

The reaction between 4-tert-butylbenzyl bromide and potassium iodide was carried out in microemulsions based on different nonionic surfactants, and the reaction rates were compared with those obtained in two-phase systems with added phase-transfer agent, either a quaternary ammonium salt or a crown ether. The reactions were relatively fast in the microemulsions and extremely sluggish in the two-phase systems without additional phase-transfer agent. Addition of a phase-transfer agent did not accelerate the reaction when a hydrocarbon was used as organic solvent, neither in the two-phase system nor in the microemulsion. When a chlorinated hydrocarbon was used as solvent, phase-transfer catalysis became effective and the rate obtained in the two-phase system with an equimolar amount of phase-transfer agent added was higher than that obtained in the microemulsion. When a catalytic amount of phase-transfer agent was used, the rate in the two-phase system was about the same as the rate obtained in the microemulsion without the phase-transfer agent. The combined approach, that is, use of a microemulsion as the reaction medium and addition of a phase-transfer agent, gave the highest reaction rate. The quaternary ammonium salt (tetrabutylammonium hydrogen sulfate) was a more efficient catalyst in the microemulsion system than the crown ether ([18]crown-6).     

An efficient solventless method for the synthesis of N,N-dialkyl sulfonamide derivatives

Aza-Michael addition of sulfonamides to α,β-unsaturated esters efficiently proceeds in the presence of catalytic amount of sodium hydroxide (NaOH) and tetrabutylammonium bromide (TBAB) as a phase-transfer catalyst (PTC) under microwave irradiation to afford N,N-dialkyl sulfonamides as biologically interesting compounds in good to excellent yields and short reaction times.     

The promoting effect of chelating ligands in the oxidative carbonylation of phenol to diphenyl carbonate catalyzed by Pd–Co–benzoquinone system

The system Pd(OAc)₂/BQ/Co(acac)₃ (BQ=benzoquinone), in combination with tetrabutylammonium bromide (TBAB) as a surfactant agent and a chelating ligand such as 2,9-dimethyl-1,10-phenanthroline (dmphen) or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmdpphen), is an efficient catalyst for the oxidative carbonylation of phenol to diphenyl carbonate (DPC). The best results have been obtained using the system Pd(OAc)₂/BQ/Co(acac)₃/dmphen=1/30/8/5 (molar ratio) in which [Pd]=10⁻³ mol l⁻¹ and TBAB/Pd=60/1. This system gives the maximum productivity of 700 mol DPC/mol Pd h at 135°C and under P_tot=60 atm (CO/O₂=10/1 molar ratio). The role of each component of the catalytic system is discussed and a catalytic cycle is proposed.     

相转移催化合成2-苯基喹啉衍生物

以喹啉(1)和取代苯肼(2a~2d)为原料,K₂S₂O₈为引发剂,TBAB为相转移催化剂,乙腈为溶剂,经自由基反应合成了4个2-苯基喹啉化合物（3a~3d, 3d为新化合物）,其结构经¹H NMR, ¹³C NMR和HR-ESI-MS表征。以3a的合成为模板反应,研究了引发剂,溶剂和反应温度对3收率的影响。结果表明：在最佳反应条件(1 1.0 mmol, 2 1.2 eq., K₂S₂O₈ 2.0 eq., TBAB 0.2 eq.,于室温反应4 h)下,3a~3d收率54%~72%。     

A carrier-free and recyclable protocol for the cross-coupling of terminal alkynes with arylboronic acids in H2O/TBAB

A new and recyclable protocol was developed for Pd(OAc)₂-catalyzed the cross-coupling reaction of terminal alkynes with arylboronic acids using environmentally friendly H₂O/TBAB as reaction medium. A series of cross-coupling products containing internal acetylenic bond can be obtained with good selectivity and yield. The Pd(OAc)₂/H₂O/TBAB system was stable in the Sonogashira-type cross-coupling reaction and could be used at least three cycles without considerable decrease in catalytic performance. The results suggest that the unsupported and recyclable systems can be extended to the other realm of CC bond formation in synthetic organic chemistry.     

Gelatin as a bioorganic reductant, ligand and support for palladium nanoparticles. Application as a catalyst for ligand- and amine-free Sonogashira-Hagihara reaction

Palladium nanoparticles were deposited and reduced by gelatin as a safe edible, naturally occurring and cheap support. No extra reducing agents were used for the generation of Pd(0) nanoparticles from the Pd(II) salt. The nanoparticles of Pd supported on gelatin were characterized by SEM, TEM and AFM images, UV-Vis and XRD spectra and the amount of palladium entrapped in the gelatin was measured by ICP and atomic absorption analysis. The nanoparticles showed high catalytic activity for the Sonogashira-Hagihara coupling reaction of various aryl iodides, bromides and chlorides as well as heteroaryl halides and also β-bromo styrene with phenylacetylene under copper-, ligand- and amine-free conditions. The reactions were carried out at 100 °C in molten tetrabutylammonium bromide (TBAB) or polyethylene glycol (PEG400) in the presence of potassium acetate as a base in argon atmosphere. Dimerization of phenylacetylene applying similar conditions in air is also described.     

Chitosan-supported palladium(0) catalyst for microwave-prompted Suzuki cross-coupling reaction in water

A chitosan-supported palladium (Pd) (0) catalyst was prepared by simple adsorption of palladium(II) ion onto chitosan beads and a subsequent reduction process. To maintain mechanical stability, the chitosan-supported palladium(0) catalyst was cross-linked with either glutaraldehyde or diglycidyl ether polyethylene glycol. The catalysts were utilized for the Suzuki cross-coupling reaction in water. The catalyst, in the presence of a tetrabutylammonium bromide (TBAB) additive, showed excellent catalytic activity in microwave-prompted Suzuki cross-coupling reactions using various aryl halides and boronic acids. In addition, the catalyst was successfully reused up to five times without significant loss of catalytic activity.     

Tandem one-Pot palladium-catalyzed reductive and oxidative coupling of benzene and chlorobenzene

The in situ combination of oxidative coupling of benzene to biphenyl and reductive coupling of chlorobenzene (also to biphenyl) using palladium catalysts (Pd(2+)/Pd(0)) is described. In each cycle, the reductive process regenerates the catalyst for the oxidative process and vice versa. Kinetic investigations show that the reaction rate depends on [C(6)H(6)], [C(6)H(6)Cl], and catalyst loading, with E(a)() = 13 kcal mol(-)(1). The reduced palladium catalyst undergoes deactivation through aggregation and precipitation, but it is observed that during this deactivation process the Pd(0) becomes an active catalyst for the reductive coupling of chlorobenzene. Accordingly, while Pd(0)/C particles are inactive, Pd(0) colloids do catalyze the tandem reaction. Conversion is increased in the presence of a phase-transfer catalyst, presumably due to stabilization of the active Pd(0) clusters. The two halves of the catalytic cycle are examined in the light of previous research, regarding analogous oxidative and reductive coupling reactions, using stoichiometric amounts of PdCl(2) and Pd(0), respectively. The roles of homogeneous PdCl(2) and Pd(0) clusters are discussed.     

One-Pot Two-Step Approach to Selenides. Phase-Transfer Catalyzed Synthesis of ω-Hydroxyalkyl Selenides

ω-hydroxyalkyl selenides were synthesized in good yields under phase-transfer conditions which involved hadrazine reduction on selenium powder and then alkylation with ω-haloalkyl alcohols in the presence of TBAB, reduction the resulting diselenides with KBH₄ followed by treatment with alkyl halides.     

Bimetallic PdAu nanoparticles as hydrogenation catalysts in imidazolium ionic liquids

Metallic and bimetallic PdAu nanoparticles were solubilized in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) by a phase-transfer method using poly(vinylpyrrolidone) (PVP) as a stabilizer. Nanoparticles were characterized by UV–vis spectroscopy and transmission electron microscopy. The bimetallic PdAu nanoparticles in the IL-phase were examined as catalysts for hydrogenation reactions; both the activity and selectivity of the hydrogenation reactions could be tuned by varying the composition of the bimetallic nanoparticles, with maximum activities seen at 1:3 Au:Pd ratios. These nanoparticles/IL catalysts were recycled and then reused for further catalytic reactions with minimal loss in activity.     

Phase-Transfer Catalysis: Acylation of β-Dicarbonyl Compounds

The alkylation of β-dicarbonyl compounds under phase-transfer conditions has been studied in detail and, in virtually all of the reported examples, the C-alkylation products have been found to predominate.^1–6 Only when the reaction rate is slow is there any evidence for O-alkylation as, for example, when there is steric hindrance to the approach of the alkylating agent to the carbanionic centre.^1,7 There is no record, however, of the corresponding acylation reactions.     

Synthesis and applications of polyvinylpyridine-grafted silica containing palladium nanoparticles as a new heterogeneous catalyst for heck and suzuki coupling reactions

A new catalytic system based on palladium nanoparticles supported on poly(4-vinylpyridine) (P4VPy)-grafted silica is introduced. Aminopropylsilica was reacted with acryloyl chloride to form acrylamidopropylsilica. Onto this functionalized silica, 4-vinylpyridine monomer was polymerized by free radical polymerization. The P4VPy-grafted silica was characterized by FT-IR spectroscopy and the amount of (P4VPy) grafted was determind by thermogravimetric analysis (TGA). The complexation of (P4VPy)-grafted silica with Pd(Cl)₂ was carried out to obtain the heterogeneous catalytic system. Transmission electron microscopy images (TEM) showed that palladium dispersed through polymer surface in nanoparticle size. This catalytic system exhibited excellent activity in cross-coupling reactions of aryl iodides, bromides and also chlorides, with olefinic compounds in Heck-Mizoraki, and with benzylbronic acid in Suzuki-Miyaura reactions. The use of aryl chlorides in cross-coupling reactions is usually hardly successful, but excellent results were gained in the presence of terta-n-butylammonium bromide (TBAB) as an additive. The turnover number (TON) of this catalyst reaches up to 9 × 10⁴ in these C-C bond forming reactions. High efficiency of the catalyst along with short reaction time, high yields, easy purification, recyclability, large scale synthesis and simple procedure are among the advantages of this catalytic system     

O-Alkylation of a lignite humic acid by phase-transfer catalysis

A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst. The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides—methyl iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and ¹H NMR, CPMAS ¹³C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all the humic reaction products. Increased nitrogen in the reaction products suggested incomplete removal of the phase-transfer catalyst after purification of the alkylated HA. ¹H NMR and CPMAS ¹³C NMR spectra of alkylated products provided evidence of the successful occurrence of the alkylation reactions. Infrared spectra confirmed the NMR results, revealing the characteristic absorption of newly formed alkyl and aryl ethers and esters in the alkylated products and C–H stretching in the aromatic ring of the benzylated derivative. These findings indicate that humic matter can be successfully alkylated with several different alkylating groups by catalysed phase-transfer reaction. This O-alkylation reaction has the advantage of being mild, versatile, and high-yielding compared with traditional methylation reactions applied to HA. The possibility of introducing different alkyl groups into the HA by a mild phase-transfer reaction may become useful by enabling improved fractionation of humic supramolecular associations and further understanding of the molecular nature of humic substances.     

Practical synthesis of biaryl colchicinoids containing 3,4-catechol ether-based A-rings via Suzuki cross-coupling with ligandless palladium in water

Eight new biaryl colchicinoids containing 3^′,4^′-methylene or benzodioxy ether bridges were synthesized. The key synthetic step employed a ligandless, aqueous Suzuki cross-coupling reaction catalyzed by Pd(OAc)₂ with tetrabutylammonium bromide (TBAB) and potassium carbonate (K₂CO₃). The biaryl Suzuki products were typically formed in 5-30 min and always in less than 1 h.     

Pd(OAc)_2/TBAB催化卤代芳烃与末端炔烃的Sonogashira交叉偶联反应研究

研究了无铜、无配体、可回收利用的催化体系[Pd(OAc)2/TBAB]催化卤代芳烃与末端炔烃的Sonogashira交叉偶联反应,高产率地合成了一系列偶联产物,其结构经1H NMR和13C NMR表征。催化实验结果表明,Pd(OAc)2/TBAB可回收重复使用3次,催化活性基本不变。