Acyclic diene metathesis (ADMET) of vinylsilanes over Re2O7–Al2O3 catalyst

Tetravinylsilane and divinylsilanes have been successfully metathesized for the first time over Re₂O₇/Al₂O₃ catalyst promoted with tetrabutyltin under mild reaction conditions. All of the products were acyclic oligomers via intermolecular metathesis; the cyclic products via intramolecular metathesis were not formed.     

Synthesis and ring-opening metathesis polymerization of eight-membered unsaturated lactams and related monomers

Novel eight-membered ring unsaturated lactams were synthesized and tested as monomers for the ruthenium-catalyzed ring-opening metathesis polymerization (ROMP). The reaction of a N-protected cyclic alkeneamine was also investigated. The Grubbs’ benzylidene complexes RuCl₂(=CHPh)(PCy₃)₂ or RuCl₂(=CHPh)(PCy₃)(IMesH₂) and selected ruthenium–arene species bearing either phosphine or stable Arduengo-type N-heterocyclic carbene ligands served as catalyst precursors. In most cases, isomerization of the starting materials took place and only 1-benzyl-1-aza-2-ketocyclooct-5-ene afforded a polymeric product. This polyamide was characterized by numerous analytical techniques.     

Efficient One-pot Synthesis of 12-Aryl-8, 9, 10, 12-tetrahydrobenzo[a]xanthen-11-ones Under Solvent-free Conditions

Multi-component condensation of 2-naphthol, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds catalyzed by ionic liquid [NSPTEA][HSO₄] was accomplished for the synthesis of a series of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones under solvent-free conditions. High yields, ease recovery, short reaction time and reusability of catalyst are significant advantages. ZrOCl₂·8H₂O was also found to act as an effective catalyst towards this transformation.     

Preparation of palladium complexes of 1,3-di(2-pyridyl)propane derivatives and their use in norbornene polymerization

A variety of neutral palladium(II) complexes [Pd(L–L)Cl₂] containing 1,3-di(2-pyridyl)propane (1), 1,3-bis(2-pyridyl)-2-pentylpropane (2), 1,3-bis(2-pyridyl)-2-phenylpropane (3a), 1,3-bis(2-pyridyl)-2-tolylpropane (4), and 1,3-bis(2-pyridyl)-2-ferrocenylpropane (5) as chelate ligands (L–L) have been synthesized. The crystal structures of 1,3-diphenyl-2,4-di-pyridin-2-yl-butan-1-ol (3b), 5, [(2)PdCl₂], [(4)PdCl₂], and [(5)PdCl₂] have been determined and show a square planar geometry at palladium(II). The neutral complexes were tested in the polymerization of norbornene and copolymerization of norbornene with norbornene derivatives. The complex bearing the pentyl group exhibited high reactivity to give up to 5.9×10⁵ in molecular weight for the homopolymerization. When [(4)PdCl₂] or [(5)PdCl₂] was used as a catalyst, homopolymers insoluble at 150 °C in trichlorobenzene were obtained. However, copolymerization of norbornene with norbornene derivatives 8a–d catalyzed by [(4)PdCl₂] gave soluble copolymers with molecular weights up to 5.1×10⁵.     

Germanium and silicon compounds as promoters for Re2O7/SiO2-Al2O3 metathesis catalysts

The effect of replacement of R₄Sn by germanium and silicon derivatives as the promoter for the catalyst system Re₂O₇/SiO₂-Al₂O₃ in the metathesis of hex-1-ene, and the system Re₂O₇/B₂O₃/SiO₂-Al₂O₃ in the metathesis of methyl oleate, was studied. The new promoters react slowly with the rhenium oxide. An activation time of about 15 min at temperatures varying from 50 to 75 °C is required for obtaining a good catalytic activity. These promoters can replace the toxic tin compounds, although they give rise to lower turnover numbers in the metathesis of methyl oleate.     

TiO2 nanoparticles as an effective catalyst for the synthesis of hexahydro-2-quinolinecarboxylic acids derivatives

The one-pot three-component reaction of arylmethylidenepyruvic acids,1,3-cyclohexandiones and ammonium acetate provides an economical and efficient synthetic route to 5-oxo-4-aryl-l,4,5,6,7,8-hexahydro-2-quinolinecarboxylic acid 4 under solvent-free conditions using a catalytic amount of TiO₂ nanoparticles（TiO₂ NPs） as an effective heterogeneous catalyst.     

胺基膦钌卡宾化合物的合成及催化烯烃复分解反应

合成并表征了一类含新型胺基膦配体的Grubbs二代型钌卡宾烯烃复分解催化剂[RuCl₂(H₂IMes)·(R¹HNPR²₂)(=CHPh)], 采用核磁共振波谱和单晶X射线衍射确定了催化剂的结构. 在室温条件下, 以N,N-二烯丙基-对甲苯磺酰胺的关环复分解反应(RCM)为模型, 考察了不同胺基膦配体对钌卡宾催化反应速率的影响. 结果表明, G2?1表现出最佳的催化活性. 通过底物研究发现, G2?1催化剂(摩尔分数, 1%)对双端烯及多端烯的RCM反应具有较好的活性和官能团适应性, 产物收率均>95%; G2?1催化剂同样适用于同(异)端烯底物的交叉复分解反应(CM), 其催化苯乙烯与3-苯氧基丙烯的CM反应时产物收率高达92%.     

Tandem sequence of cross metathesis--ring-closing metathesis reaction of alkynyl silyloxy-tethered enynes

A tandem cross metathesis (CM)--ring-closing metathesis (RCM) sequence to form cyclic siloxanes is reported. This new enyne metathesis platform expands the scope and utility of the regio- and stereoselective cross metathesis reaction between silylated alkynes and terminal alkenes. The initial cross metathesis was directed to occur on the alkyne by employing sterically hindered mono-, di-, and trisubstituted alkenes tethered to the alkyne via silyl ether. The regio- and stereoselectivity feature of the initial CM step in this tandem CM-RCM process is identical to that of the CM reactions of silylated alkynes and alkenes. This tandem sequence provides both synthetically useful silylated 1,3-diene building blocks and insights into the reaction mechanism of the enyne metathesis reaction.     

Hydrogenation of non-activated alkenes catalysed by water-soluble ruthenium carbonyl clusters using a biphasic protocol

The use of the water soluble ruthenium clusters Ru₃(CO)_12−x(TPPTN)_x (x=1 1, 2 2 or 3 3) and H₄Ru₄(CO)₁₁(TPPTN) 4 (TPPTN=P{m-C₆H₄SO₃Na)₃) as catalyst precursors in the hydrogenation of non-activated alkenes under biphasic conditions is described. Each cluster displays activity under moderate conditions, ca. 60 atm. H₂ at 60°C, with catalytic turnovers up to ca. 500. The trinuclear clusters undergo transformation during reaction but can be reused repeatedly without loss of activity. Other methodologies such as ionic liquid–organic and the use of silica supports have been attempted with these clusters but they are less effective than the aqueous–organic regime.     

Silane-induced ring-opening polymerization of 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane catalyzed by a triruthenium cluster

The silane-induced ring-opening polymerization of a cyclic siloxane, 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane (2), is catalyzed by a ruthenium cluster, (μ₃,η²:η³:η⁵-acenapthylene)Ru₃(CO)₇ (1), to give poly(tetramethylsilethylenesiloxane) with M_n=6300–780,000 and M_w/M_n=1.5–3.0. The molecular weight of the polymer can be controlled by changing the concentration of the monomer solution. Addition of acetone results in formation of the polymer with M_n=4400, spectroscopic analysis of which reveals existence of a siloxy and an isopropoxy moieties at the end group.     

Iron Chloride Hexahydrate-catalyzed Friedel-Crafts Akylation of Cyclic Ketene Dithioacetals with Alcohols

A cost-effective and environmentally compliance FeCl₃·6H₂O catalyzed Friedel-Crafts alkylation of cyclic ketene dithioacetals with alcohols was developed. The reaction was efficient in the presence of catalyst loading as low as 5%(molar fraction) in CH₂Cl₂ solvent at room temperature or under reflux conditions. A wide range of alkylated ketene dithioacetals were synthesized in excellent yields.     

New dense fluoroalkyl-substituted imidazolium ionic liquids

New mono and polyfluoroalkyl-substituted ionic liquids have been synthesized and characterized. The neat reaction of 1-methylimidazole (1a) with 1,1,1-trifluoro-3-iodopropane (2a) at 80°C formed the quaternary salt, 1-methyl-3-trifluoropropylimidazolium iodide (3), in 90% yield. Similarly, sodium imidazole (1b) gave good yields of the quaternary salts, 1,3-bis(trifluoropropyl)imidazolium iodide (3b) with an excess of 2a, and 1,3-bis(monofluoropropyl)imidazolium bromide (3c) with an excess of 1-fluoro-3-bromopropane (2b). In water as solvent, metathesis reactions of 3 with KPF₆, LiN(SO₂CF₃)₂ and KSO₃CF_3, and of 3b and 3c with KPF₆ and LiN(SO₂CF₃)₂ led to 4a–c, 4d,e, and 4f,g, respectively, in good isolated yields. Some of the di(polyfluoroalkyl)imidazolium salts are liquids with densities in excess of 1.8 g/cm³.     

Selective oxidation of methane to formaldehyde over antimony oxide-loaded catalyst

A possibility of antimony oxide as a catalyst for the selective oxidation of methane with oxygen to formaldehyde was investigated. The activity measurement was carried out at an atmospheric pressure and at 873 K, where the homogeneous gas-phase reaction was negligible. Oxidized diamond (O-Dia)-supported antimony oxide catalyst produced 1.3 mmol h⁻¹ g-cat⁻¹ of formaldehyde with a formaldehyde selectivity of 23%. On the other hand, SiO₂ supported antimony oxide catalyst exhibited negligible catalytic activity. XRD and UV–vis analyses revealed that -Sb₂O₄ was formed on the oxidized diamond while Sb₆O₁₃ was formed on SiO₂. Selective oxidation of methane to formaldehyde seemed to proceed on -Sb₂O₄ with moderate activity and selectivity to formaldehyde, via a redox cycle of -Sb₂O₄ and Sb₂O_4−x. On the other hand, Sb₆O₁₃ on SiO₂ was stable under the reaction conditions and the selective oxidation occurred only slightly.     

由高效双键易位闭环反应合成环状聚ε-己内酯

研究了合成环状大分子的一种新方法,即借助活性开环聚合反应和高效双键易位闭环反应(RCMR)合成环状聚ε-己内酯.首先,ε-己内酯在环状引发剂2,2-二丁基-2-锡-1,3-二氧环庚烷(DSDOP)的作用下,进行活性开环聚合反应,获得双羟基封端的聚ε-己内酯(PCLOH);然后,在对甲苯磺酸、1,3-二环己基碳二亚胺(DCC)和4-二甲氨基吡啶(DMAP)的作用下,将PCLOH与3-丁烯酸反应转化为双烯丙基封端的聚ε-己内酯(allylPCL);在Grubbs催化剂(Cl2(Cy3)2Ru CHPh)的作用下,将allylPCL经RCMR环化成环状聚ε-己内酯,并采用SEC,NMR,TGA以及DSC等技术对聚合物的结构和热力学性能进行了表征,SEC和黏度表征结果显示环状聚ε-己内酯具有较小的动态力学体积,TGA和DSC表征结果显示环状聚ε-己内酯的热分解温度较其线型前体高13℃,环化的结果使其熔点和结晶度下降.结果表明allylPCL在较稀(2.5×10-5mol/L)体系中,借助Grubbs催化剂进行的RCMR分子内环化反应效率高,环化产物无需进一步分离提纯.     

钨含量对W/SiO2/Al2O3催化剂上1-丁烯自歧化反应的影响

采用浸渍法制备了一系列钨负载量不同的W/SiO₂/Al₂O₃ 催化剂. 采用X 射线衍射(XRD)、激光拉曼(Raman)光谱、紫外-可见(UV-Vis)光谱、氢气程序升温还原(H₂-TPR)和氨程序升温脱附(NH₃-TPD)等技术对催化剂进行了表征. 实验结果表明: 钨的负载量对催化剂上氧化钨物种的分散程度、还原性以及催化剂的酸性有非常重要的影响. 对该类催化剂上1-丁烯自歧化反应进行了详细考察, 结果表明: 当钨的质量分数为6.0%时,W/SiO₂/Al₂O₃催化剂表现出最佳的歧化活性和稳定性. 原因在于6.0%的钨负载量可以使催化剂上氧化钨物种具有中等程度的分散性、合适的还原性, 并且使催化剂具有一定程度的酸性, 这些因素有利于在催化剂上形成烯烃歧化活性位.     

负载型钾盐催化剂用于合成苯甲醚的研究

采用固定床连续进料的反应器代替传统间歇反应釜作为评价反应器,以环境友好的碳酸二甲酯为甲基化试剂,由苯酚合成苯甲醚的反应新工艺。采用SiO2负载的钾盐类催化剂,考察了反应温度、进料空速、原料配比、活性组分负载量以及催化剂用量等对反应性能的影响。研究表明,在该负载型钾盐催化剂上苯酚的转化率均较高,且生成苯甲醚的选择性较好。尤其是在KF/SiO2催化剂上,在DMC/苯酚摩尔比为2∶1,进料空速为2 h-1,反应温度为250℃时,苯甲醚收率和选择性分别高达93.93%和98.19%。而且该负载型催化剂活性比较稳定,未发现活性组分流失,反应运行16 h催化剂未见失活。     

Heteropolyacid–silica mediated [3+2] cycloaddition of azomethine ylides—a facile multicomponent one-pot synthesis of novel dispiroheterocycles

An efficient synthesis of dispiroindenoquinoxaline pyrrolizidine derivatives has been expediently accomplished by a one-pot four component 1,3-dipolar cycloaddition reaction. High regioselectivity was achieved using heteropolyacid H₄[Si(W₃O₁₀)₃]–silica as a catalyst. X-ray diffraction studies of one of the cycloadducts proved the structure and regiochemistry of the cycloadduct.     

A simple and efficient one-pot synthesis of 1,4-dihydropyridines using heterogeneous catalyst under solvent-free conditions

One-pot condensation of β-dicarbonyl compounds with aldehydes and ammonium acetate in the presence of HClO₄–SiO₂ at 80 °C under solvent-free conditions with good to excellent yields. The catalyst is easily prepared, stable, reusable and efficiently used under reaction conditions.     

Synthesis of 4a-carba-β-l-lyxofuranose, 4a-carba-β-l-arabinofuranose and 2,2,5-trimethyl-3a,6a-dihydro-cyclopenta[1,3]dioxol-4-one using Mn/CrCl3 mediated domino reactions and ring closing metathesis

A common method for the synthesis of 4a-carba-β-l-lyxofuranose and 4a-carba-β-l-arabinofuranose from d-mannose and 2,2,5-trimethyl-3a,6a-dihydro-cyclopenta[1,3]dioxol-4-one from d-ribose is described using catalytic Nozaki-Hiyama-Kishi (NHK) conditions and ring closing metathesis (RCM). In this transformation, ω-deoxy-ω-iodo manno/ribo furanoside undergoes reductive elimination in the presence of Mn/CrCl₃ to give the corresponding olefin-aldehyde which was trapped by nucleophile under the same conditions to afford the desired diolefinic species. The ring closing metathesis reaction on these diolefinic species with Grubbs second generation catalyst produced the required carbocycles.