Hydrosilylation of unsaturated fluorinated esters and ethers with hydrochlorosilanes

Hydrosilylation of allyl esters of fluoro acids and ethers of fluoro alcohols with hydrochlorosilanes in the presence of the Speier’s catalyst was studied. Yields of adducts with ethers reach 62–68%, and with esters, 27–45%. By etherification of the adduts with ethers the respective ethoxysilanes were obtained in 41–43% yield. The latter reaction even in very mild conditions is complicated by the formation of a large amount of siloxanes. Yield of siloxanes is 22–32%.     

Transesterification of esters of adipic acid

Conclusions The corresponding higher esters were produced in good yields by transesterification of lower esters of adipic acid by alcoholysis with alcohols in the presence of an alkaline or acid catalyst. Acid catalysts (p-toluenesulfonyl chloride) are more effective than alkaline catalysts (KOH).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2439–2443, November, 1971.     

New optically active poly（amide-imide）s derived from N, N′-（4,4-diphthaloyl）-bis-L-leucine and hydantoin derivatives： Synthesis and properties

Six new optically active poly(amide-imide)s(5a-f) were synthesized through the direct polycondensation reaction of N,N'-(4,4'- diphthaloyl)-bis-L-leucine(3) with six hydantoin derivatives(4a-f).Triphenyl phosphite(TPP)/pyridine in the presence of calcium chloride(CaCl_2) and N-methyl-2-pyrrolidone(NMP) were successfully applied for direct polycondensation.The polycondensation reactions produce a series of new poly(amide-imide)s(5a-f) in high yields,and inherent viscosity between 0.42 and 0.55 dL/g.The re...     

Ring-opening metathesis polymerization (ROMP) of isomerically pure functional monomers and acyclic diene metathesis depolymerization (retro-ADMET) of functionalized polyalkenamers

ROMP and retro-acyclic diene metathesis (ADMET) were used for the synthesis of new functional polymers and functional oligomers, respectively. Purely exo and enantiomerically pure norbornene and 7-oxanorbornene derivatives were prepared using stereospecific synthesis, effective fractionation and high yield condensation reactions. Successful ROMPs of those monomers were performed using either the new carbenic Schrock’s or Grubb’s catalysts or in some cases a classical bicomponent catalyst. New functional polymers such as optically active poly(norbornene-2-carboxylic acid), reactive poly(norbornene-2-azlactone), and side-chain liquid crystal polyoxanorbornenes were fully characterized. On the other hand, successful depolymerizations of 1,4-polyisoprene and of epoxidized 1,4-polybutadiene via cross-metathesis with 4-octene were performed using a stabilized bicomponent catalyst and the Grubb’s catalyst, respectively. Conditions for the controlled synthesis of epoxidized oligobutadienes and of epoxydienic monomers via retro-ADMET were clearly defined.     

Dendronized polystyrene supports for new catalytic systems

New catalytic systems based on tris(dimethylvinyl)methyl substituted polystyrene were prepared. Dendronized polystyrenes were obtained by modification of poly(styrene-co-chloromethylstyrene) precursors with LiC(SiMe₂CHCH₂)₃. Platinum was attached to the polymers via coordination to vinyl groups located on carbosilane moieties. Such the catalytic system makes an interesting alternative for heterogenous platinum catalysts (Pt/charcoal, Pt/C_act and Pt/Al₂O₃) and also to Karstedt’s catalyst, when used in hydrosilylation of vinylsilanes.     

Dehydrogenative coupling as an efficient route to ferrocene functionalized siloxanes

Ferrocene grafted siloxanes were prepared in high yields (∼79-97%) via Rh-catalyzed dehydrogenative coupling of a series of monomeric, polymeric, and cyclic hydrosiloxanes with ferrocenemethanol. Wilkinson’s catalyst was the most efficient of those surveyed (Karstedt’s catalyst, H₂PtCl₆, Co₂(CO)₈, 10% Pd/C, 10% Pt/C, 5% Rh/C) with respect to yield and selectivity. Benzene and toluene were better solvents than tetrahydrofuran and methylene chloride.     

稀土金属盐促进的Mo-Co-K硫化物基催化剂用于合成气选择性制乙醇等低碳混合醇

采用超声法在非水溶剂介质中制备了稀土金属La盐等促进的硫化钼基催化剂,考察了其CO加氢选择性合成乙醇等低碳混合醇的催化性能.在3.0MPa,330℃和H2/CO(体积比)=2.0的反应条件下,La促进的催化剂表现出较Mo-Co-K硫化物基催化剂更高的催化活性,CO转化率和产物中乙醇的分布可分别达到17.2%和53.4%.扫描电镜、透射电镜、X射线衍射和光电子能谱等表征结果表明,稀土金属La盐的加入改善了Mo-Co-K硫化物基催化剂的外观形貌和电子结构,对提高催化活性和乙醇的分布起到重要的作用.     

Synthesis of dimethyl carbonate by vapor phase oxidative carbonylation of methanol over Cu-based catalysts

Dimethyl carbonate (DMC) synthesis reaction by oxidative carbonylation of methanol has been studied using vapor phase flow reaction system in the presence of Cu-based catalysts. A series of Cu-based catalysts were prepared by the conventional impregnation method using activated carbon (AC) as support. The effect of various promoters and reaction conditions on the catalytic reactivities were intensively evaluated in terms of methanol conversion and DMC selectivity. The morphological analysis by X-ray diffraction and SEM was also conducted in order to characterize the emloyed catalysts. Regardless of catalyst compositions, the optimal reaction temperature for oxidative carbonylation of methanol was found to be around 120–130°C. The reaction rate was too slow below 100°C, while too much by-products was produced above 150°C. Among the various catalysts employed, CuCl₂/NaOH/AC catalyst with the molar ratio of OH/Cu=0.5–1.0, has shown the best catalytic performance, which appears to have a strong relationship with the formation of intermediate species, Cu₂(OH)₃Cl.     

Rhodium-benzimidazolidin-2-ylidene catalyzed addition of arylboronic acids to aldehydes

Six rhodium–carbene complexes (2a–f) have been prepared and the new compounds characterized by C, H, N analyses, ¹H-n.m.r. and ¹³C-n.m.r. Phenylboronic acid reacts with aldehydes in the presence of a catalytic amount of rhodium(I)–carbene complex, RhCl(COD)(1,3-dialkylbenzimidazolidin-2-ylidene), (2a–f), to give the corresponding aryl secondary alcohols in good yields.     

Triallyl(aryl)silanes serve as a convenient agent for silicon-based cross-coupling reaction of aryl halides

Triallyl(aryl)silanes, stable and easily accessible arylsilanes, were found to react with aryl bromides in the presence of a palladium catalyst (PdCl₂-PCy₃) and tetrabutylammonium fluoride (TBAF) in good yields. The scope of the reaction is broad, and a wide variety of functional groups are tolerant. Allyl groups on Si are readily cleaved upon treatment with TBAF to form fluorosilanes, silanepolyols, siloxanes and/or their mixed forms, which might be responsible for high efficiency of the reaction.     

Facile Synthesis of Tris(alkoxydimethylsilyl)methane Derivatives via Alcoholysis Under Open-Flask and Mild Conditions

The reactions between a variety of functionalized alcohols and tris(dimethylsilyl)methane, (HMe₂Si)₃CH, are described. Alcohols such as ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, triethylene glycol monomethyl ether, 2-chloroethanol, 1-octanol, benzyl alcohol, glycidol, and allyl alcohol were converted in the presence of Karstedt's catalyst into the corresponding tris(alkoxydimethylsilyl)methanes, (ROMe₂Si)₃CH, in a convenient one-pot operation under aerobic conditions. The appearance of the products coincides with the generation of colloidal Pt(0) species. Moreover, poly(4-chloromethyl)styrene containing tris(dimethylsilyl)methyl groups reacts with benzyl alcohol or 2-chloroethanol in the presence of Karstedt's catalyst to give new macromolecules bearing tris(alkoxydimethylsilyl)methyl groups. The reaction rate is greatly influenced by the concentration of catalyst.     

Formation of Ethers from Alcohols with Chloride Complexes of Platinum(II) as Catalysts

A new catalytic reaction of the etherification of alcohols in the system ROH-PtCl ₄ ²⁻ has been observed. At 70 °C in the presence of catalytic amounts of chloride complexes of platinum(II) methanol gave dimethyl ether. Methyl tert-butyl ether and di-tert-butyl ether were formed analogously from a mixture of methanol and tert-butanol. In the reaction with ethanol the products were diethyl ether and a π-ethylene complex of platinum(II). It is suggested that the step-wise mechanism includes the oxidative addition of the alcohol with the intermediate formation of an alkyl complex of platinum(IV), the decomposition of which by reductive elimination under the influence of a second molecule of alcohol or an alkoxide anion gives an ether and regenerates the catalyst, a chloride complex of platinum(II).__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 3, pp. 190–193, May–June, 2005.     

Amine groups functionalized gel-type resin supported Pd catalysts: Physicochemical and catalytic properties in hydrogenation of alkynes

Palladium catalysts (0.125–0.5 wt.% Pd) supported by amine groups—functionalized gel-type resin (FCN) were studied in the hydrogenation of alkynes reagents, 2-butyne-1,4-diol and phenylacetylene. The catalysts were prepared by two routes. The first, “OAc” is based on the immobilization of Pd-precursor in the pre-swollen resin from THF solution of Pd(OAc)₂, followed by chemical reduction of the Pd-centers. This method produces Pd particles of size in nano-scale. The second procedure, “aq” implies the deposition of Pd-species on dry resin beads using aqueous solution of PdCl₂. Reduction of these Pd-species gives relatively large Pd particles, dominating are 30–50 nm in size. The SEM studies performed over the cross-section of catalysts grains showed location of Pd in outer shell of polymer beads in both “OAc” and “aq” catalysts; however, thinner layer of Pd appears in “aq” series catalysts. In the presence of all catalysts, prepared by “OAc” and “aq” methods the selectivity towards alkenes is high, above 90%. The catalysts of “aq’ series are much more active and more selective than “OAc” analogues giving selectivity to alkene ca. 94% at almost complete conversion of alkynes. Moreover, catalytic performance of “aq’ series catalyst is unchanged under recycling use. The catalyst was recovered and reused 4 times, maintaining its catalytic efficiency.     

An effective method for the synthesis of carboxylic esters and lactones using substituted benzoic anhydrides with Lewis acid catalysts

An efficient mixed-anhydride method for the synthesis of carboxylic esters and lactones using benzoic anhydride having electron withdrawing substituent(s) is developed by the promotion of Lewis acid catalysts. In the presence of a catalytic amount of TiCl₂(ClO₄)₂, various carboxylic esters are prepared in high yields through the formation of the corresponding mixed-anhydrides from 3,5-bis(trifluoromethyl)benzoic anhydride and carboxylic acids. The combined catalyst consisting of TiCl₂(ClO₄)₂ together with chlorotrimethylsilane functions as an effective catalyst for the synthesis of carboxylic esters from free carboxylic acids and alcohols with 4-(trifluoromethyl)benzoic anhydride. Various macrolactones are prepared from the free ω-hydroxycarboxylic acids by the combined use of 4-(trifluoromethyl)benzoic anhydride and titanium(IV) catalysts together with chlorotrimethylsilane under mild reaction conditions. The lactonization of trimethylsilyl ω-(trimethylsiloxy)carboxylates using 4-(trifluoromethyl)benzoic anhydride is also promoted at room temperature in the presence of a catalytic amount of TiCl₂(ClO₄)₂. An 8-membered ring lactone, a synthetic intermediate of cephalosporolide D, is successfully synthesized according to this mixed-anhydride method using 4-(trifluoromethyl)benzoic anhydride by the promotion of a catalytic amount of Hf(OTf)₄.     

K-Mo基催化剂的表面酸性与其合成醇选择性

对500℃和800℃焙烧制得的氧化态K－MoO3／γ－AlO3，K－MoO3／SiO2及非负载K－Mo催化剂进行硫化后，测试其合成醇活性．结果表明500℃焙烧制得的负载型催化剂显示较高的合成低碳烃活性和较低的合成低磷醇选择性，经800℃焙烧后，合成低磷醇的选择性大幅度提高．500℃焙烧的非负载K－Mo催化剂显示较高的合成醇选择性，经800℃焙烧后，促碳醇的选择性保持不变．用氨的吸附及TPD方法测定了各样品的酸性，并与催化剂活性对照，发现催化剂酸性越强，酸量越大，则其合成醇选择性越低．催化剂上的乙醇分解实验证实，催化剂的酸量大小与它的醇分解活性成正变关系，这些结果说明催化剂酸性对其合成醇性能有直接的影响．     

Polycondensation of haloarylketones catalyzed by palladium compounds bearing N-heterocyclic carbene (NHC) ligands

Palladium-catalyzed α-arylation of ketones, which can efficiently give coupling products by using appropriate ligands and bases, could be applied to a polycondensation reaction. Stable N-heterocyclic carbenes (NHC) were used as favorable ligands coordinating the Pd catalysts, which were generated in situ from commercially available palladium compounds such as Pd(OAc)₂ and Pd₂(dba)₃ as suitable catalyst precursors in this polymerization. Using small amounts of binary catalysts, poly(aryl alkyl ketone)s were afforded in high yields from haloarylketones in the presence of a base. A primarily prepared palladium catalyst having an NHC ligand, [Pd(OAc)₂(NHC)], also efficiently catalyzed the polycondensation, whereas a palladium compound bearing two carbene ligands, [PdX₂(NHC)₂], did not.     

Highly effective and chemoselective hydrodeoxygenation of aromatic alcohols

Effective hydrodeoxygenation (HDO) of aromatic alcohols is very attractive in both conventional organic synthesis and upgrading of biomass-derived molecules, but the selectivity of this reaction is usually low because of the competitive hydrogenation of the unsaturated aromatic ring and the hydroxyl group. The high activity of noble metal-based catalysts often leads to undesired side reactions (e.g., saturation of the aromatic ring) and excessive hydrogen consumption. Non-noble metal-based catalysts suffer from unsatisfied activity and selectivity and often require harsh reaction conditions. Herein, for the first time, we report chemoselective HDO of various aromatic alcohols with excellent selectivity, using porous carbon–nitrogen hybrid material-supported Co catalysts. The C–OH bonds were selectively cleaved while leaving the aromatic moiety intact, and in most cases the yields of targeted compounds reached above 99% and the catalyst could be readily recycled. Nitrogen doping on the carbon skeleton of the catalyst support (C–N matrix) significantly improved the yield of the targeted product. The presence of large pores and a high surface area also improved the catalyst efficiency. This work opens the way for efficient and selective HDO reactions of aromatic alcohols using non-noble metal catalysts.

Porous carbon–nitrogen hybrid material-supported Co catalysts can effectively promote the chemoselective hydrodeoxygenation reaction of a various of aromatic alcohols in ethanol and hydrogen atmosphere, under relatively mild conditions.     

Chemoselective nucleophilic arylation and single-step oxidative esterification of aldehydes using siloxanes and a palladium-phosphinous acid as a reaction switch

Aldehydes and siloxanes form methyl esters in a single step through mild oxidative esterification in the presence of a palladium catalyst or, alternatively, afford secondary alcohols via TBAF-promoted arylation in the absence of a catalyst at increased temperatures under otherwise identical reaction conditions.     

Siloxane‐mediated ethylene oligomerization with iron‐based catalysts: Retarding the polymer formation

This article describes an effective strategy for retarding the simultaneous polymer formation during the ethylene oligomerization with bis(imino)pyridine iron catalysts, by addition of siloxanes as modifiers into such systems. The concurrent effects of a suitable siloxane [e.g., tetraethyl orthosilicate (TEOS), cyclohexylmethyldimethoxysilane (CHMMS), or dicyclopentyldimethoxysilane (DCPMS)] are to increase the activity for the soluble oligomers and dramatically decrease the activity for the insoluble polymers, thus synergistically making a pronounced reduction of the polymer share in the total products. Based on the experimental facts when commercial methylaluminoxane (MAO), trimethylaluminum (TMA)‐depleted MAO, and trialkyl aluminums (e.g., TMA) are applied as co‐catalyst, respectively, the functional mechanism of siloxanes is preliminarily discussed. It is proposed that TMA containing in the commercial MAO makes little contribution to the final product but lowers the activity. And, there may be a close relationship between the anionic MAO cages and the insoluble polymer production. The influence of siloxanes exert on the catalyst systems could be a comprehensive result of the interactions between siloxanes and the catalytic components, through the modulation on both the electronic and steric effects of the active centers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2748–2759     

Ruthenium and enzyme-catalyzed dynamic kinetic resolution of alcohols

Ruthenium acts as a good catalyst for the racemization reaction of secondary alcohols and amines. Ruthenium-catalyzed racemization is coupled with enzymatic kinetic resolution to prepare chiral compounds in 100% theoretical yield. Ten ruthenium complexes (1–10) act as a good catalyst the for racemization reaction and are also compatible with DKR process. Two other ruthenium complexes [RuCl₂(PPh₃)₃] and [Cp^*RuCl(COD)] are active for racemization reaction but their successful compatibility with DKR has not yet been reported. Ru/γ-Al₂O₃ and Ru–HAP are the heterogeneous catalysts used for the racemization reaction. They have also not been employed for DKR process. Polymer supported ruthenium is employed as a reusable racemization catalyst for aerobic DKR of alcohols.