93-96-9

We report the cross-dehydrative reaction of two alcohols to form unsymmetrical ethers using NHC-gold(i) complexes (NHC = N-heterocyclic carbene). Our progress in developing this reaction into a straightforward procedure is discussed in detail. The optimised methodology proceeds under mild reaction conditions and produces water as the sole by-product. The synthetic utility of this environmentally benign methodology is exemplified by the formation of a range of new ethers from readily available phenols bearing electron withdrawing substituents and secondary benzylic alcohols with various substituents. Finally, we present experimental results to account for the chemoselectivity obtained in these reactions.

Gold nanoparticles (Au-NPs) of 8 nm average diameter were obtained by thermal reduction under nitrogen from KAuCl4 in the presence of n-butylimidazol dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIm+BF4-). Characterization of the Au-NP was done by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Catalytic activities of the Au-NP/IL dispersion were evaluated in the oxidation of 1-phenylethanol at 100 and 160 °C under 4 bar pressure of dioxygen in a base-free system. Au-NP in combination with the radical initiator N-hydroxyphthalimide (NHPI) showed good conversion and selectivity for the oxidation of 1-phenylethanol to acetophenone through formation of an α-hydroxy carbon radical. The concomitant side products di(1-phenylethyl)ether and di(1-phenylethyl)peroxide were rationalized by an equilibrium due to the IL matrix of the α-hydroxy carbon radical with the 1-phenylethoxy radical. Maximum turnover number was ～5200 based on the total number of moles of gold but a factor of about six larger, TON ≈ 31 300, when only considering the Au-NP surface atoms. The fraction (N S/NT) of exposed surface atoms (NS ≈ 2560) for an average 8 nm Au-NP (having NT ≈ 15 800 atoms in a ～17-shell icosahedral or cuboctahedral particle) was estimated here as 0.16.

An expedient, efficient, economical, environmentally benign, and solvent free amidation protocol of benzhydrols with less reactive nitrogen nucleophiles assisted by propylphosphonic anhydride (T3P) under microwave irradiation has been developed. The methodology has been deployed for a wide range of heterocycles and electron-withdrawing & electron-donating groups. The protocol resulted in good to excellent yields under the given conditions (26 examples, 68-93% yield).

Although symmetrical ethers can be synthesized easily from alcohols, synthesis of unsymmetrical ethers by dehydrative cross-coupling of alcohols is still a challenge. While dehydrative cross-coupling is environmentally appealing due to formation of water as the only byproduct, the chances for formation of symmetrical ethers always exist. The existing transition metal based methods give good selectivity, but the catalyst are costly and not readily available. Here, we present a simple, readily available, and cost-effective catalyst in the form of molecular iodine which catalyzes a highly selective cross-coupling of benzylic alcohols with benzyl, alkyl, and aryl alcohols to give their corresponding unsymmetrical ethers in good to excellent yield.

The invention provides a borane-catalyzed symmetric ether synthesis method, which is characterized in that alcohol is used as a raw material, and under the catalysis of B(2,6-Cl2C6H3) (p-HC6F4) 2, etherification reaction is carried out through intermolecular dehydration to generate ether. The reaction process is simple, mild, pollution-free and efficient.

The synthesis of complex molecules like active pharmaceutical ingredients typically requires multiple single-step reactions, in series or in a modular fashion, with laborious purification and potentially unstable intermediates. Cascade processes offer attractive synthetic remediation as they reduce time, energy, and waste associated with multistep syntheses. For example, triarylmethanes are traditionally prepared via several synthetic steps, and only a handful of cascade routes are known with limitations due to high catalyst loadings. Here, we present an expedient catalytic cascade process to produce triarylmethanes. For this purpose, we have developed a bifunctional iridium system as the efficient catalyst to build heterotriaryl synthons via reductive Friedel-Crafts alkylation from ketones, arenes, and hydrogen. The catalytically active species were generated in situ from a robust triazolyl iridium(III) hydride complex and acid and is composed of a metal-bound hydride and a proximal ligand-bound proton for reversible dihydrogen release. These complexes catalyze the direct hydrogenation of ketones at slow rates followed by dehydration. Appropriate adjustment of the conditions successfully intercepts this dehydration and leads instead to efficient C-C coupling and Friedel-Crafts alkylation. The scope of this cascade process includes a variety of carbonyl substrates such as aldehydes, (alkyl)(aryl)ketones, and diaryl ketones as precursor electrophiles with arenes and heteroarenes for Friedel-Crafts coupling. The reported method has been validated in a swift one-step synthesis of the core structure of a potent antibacterial agent. Excellent yields and exquisite selectivities were achieved for this cascade process with unprecedentedly low iridium loadings (0.02 mol %). Moreover, the catalytic activity of the protic system is significantly higher than that of an N-methylated analogue, confirming the benefit of the Ir-H/N-H hydride-proton system for high catalytic performance.

Direct nucleophilic substitution of alcohols with thiols or carbon nucleophiles was achieved using a mesoporous silica-supported oxovanadium catalyst (VMPS4). Benzyl and allyl alcohols were compatible in this reaction under mild conditions, affording the products in high yields. The VMPS4 catalyst showed excellent chemoselectivity toward alcohols in the presence of acid-labile functional groups, which is in contrast to that observed for the commonly used Lewis acid catalysts, which exhibit poor selectivity. The VMPS4 catalyst could be recycled by simple centrifugation, and the catalytic activity was maintained over seven cycles.

An inexpensive, easily available, environmentally benign, and efficient catalyst molybdenum(VI) dioxo (acetylacetonate)2 was used for the direct oxo- and thioetherification of alcohol. This method endures selective molybdenum catalyzed dehydrative synthesis of symmetrical ethers from benzylic secondary alcohols as well as unsymmetrical ethers from the reaction of benzylic secondary alcohols with primary alcohol. Furthermore, we have been also successful in the synthesis of Aryl thioether by using alcohol and thiols.

The invention discloses a method for synthesizing ether by catalyzing alcohol through trimethyl halosilane. According to the method, under the conditions of air or nitrogen atmosphere, no solvent andno transition metal catalyst, an alcohol compound is directly used as a raw material, trimethyl halosilane is used as a catalyst, and symmetric or asymmetric ether is synthesized through one-step selective dehydration reaction. According to the method, the use of strong acid, strong base and organic primary halides with high toxicity, instability and higher price is avoided, the synthesis steps are shortened, the synthesis efficiency is improved, the reaction has good selectivity, and a target ether product can be obtained preferentially.

A new efficient strategy to access benzylic carbamates through C-H activation is reported. The use of a catalytic amount of a Cu(i)/diimine ligand in combination with NFSI ((PhSO2)2NF) or F-TEDA-PF6 as oxidants and H2NCO2R as an amine source directly leads to the C-N bond formation at the benzylic position. The mild reaction conditions and the broad substrate scope make this transformation a useful method for the late-stage incorporation of a ubiquitous carbamate fragment onto hydrocarbons. This journal is

Novel bidentate N-heterocyclic carbene-phosphine iridium complexes have been synthesized and evaluated in the hydrogenation of ketones. Reported catalytic systems require base additives and, if excluded, need elevated temperature or high pressure of hydrogen gas to achieve satisfactory reactivity. The developed catalysts showed extremely high reactivity and good enantioselectivity under base-free and mild conditions. In the presence of 1 mol % catalyst under 1 bar hydrogen pressure at room temperature, hydrogenation was complete in 30 minutes giving up to 96 % ee. Again, this high reactivity was achieved in additive-free conditions. Mechanistic experiments demonstrated that balloon pressure of hydrogen was sufficient to form the activate species by reducing and eliminating the 1,5-cyclooctadiene ligand. The pre-activated catalyst was able to hydrogenate acetophenone with 89 % conversion in 5 min.

Novel pyridyl-triazolylidene iridium(III) hydride complexes have been synthesized through modification of the analogous iridium chloride complexes. The dehydration of alcohols was used to probe the catalytic potential of the iridium chloride compounds and the influence of the electronic modification on the pyridyl-triazolylidene ligand scaffolds. The incorporation of electron donor substituents on the triazolylidene heterocycle considerably enhanced the catalytic activity of the coordinated iridium center towards the catalytic dehydration of alcohols. Moreover, the iridium hydride compounds are switchable catalysts that perform either alcohol dehydration or dehydrogenation. Their selectivity was predictably triggered by the presence or absence of HPF6 in the catalytic reaction.

The direct intramolecular stereospecific substitution of the hydroxyl group in enantiomerically enriched secondary benzylic, allylic, propargylic, and alkyl alcohols was successfully accomplished by phosphinic acid catalysis. The hydroxyl group was displaced by O-, S-, and N-centered nucleophiles to provide enantioenriched five-membered tetrahydrofuran, pyrrolidine, and tetrahydrothiophene as well as six-membered tetrahydroquinolines and chromanes in up to a 99% yield and 100% enantiospecificity with water as the only byproduct. Mechanistic studies using both experiments and calculations have been performed for substrates generating 5-membered heterocycles. Rate studies show dependences in a catalyst, an internal nucleophile, and an electrophile, however, independence in an external nucleophile, an electrophile, or water. Kinetic isotope effect studies show an inverse KIE of kH/kD = 0.79. Furthermore, phosphinic acid does not promote SN1 reactivity. Computational studies support a bifunctional role of the phosphinic acid in which activation of both nucleofuge and nucleophile occurs in a bridging SN2-type transition state. In this transition state, the acidic hydrogen of phosphinic acid protonates the leaving hydroxyl group simultaneously as the oxo group partially deprotonates the nucleophile. Thereby, phosphinic acid promotes the substitution of the nonderivatized hydroxyl group in enantioenriched secondary alcohols by uncharged nucleophiles with conservation of the chirality from the alcohol to the heterocycle.

Secondary benzylic alcohols represent a challenging class of substrates for N-alkylation of amines. Herein, we describe an iron(II)-catalyzed eco-friendly protocol for N-alkylation of secondary arylamines with secondary benzyl alcohols through a carbocationic pathway instead of the known borrowing hydrogen transfer (BHT) approach. Transiently generated carbocations, produced from alcohols via self-condensation, were coupled with arylamines to provide highly functionalized amine products. The scope of this methodology involves N-alkylation of primary, secondary and heterocyclic amines with primary/secondary benzylic, allylic and heterocyclic alcohols, which are common key structures in numerous pharmaceuticals drugs. The method can also be easily adopted for the amination of various natural products. (Figure presented.).

A novel, well-defined molecular Cp*CoIII complex was isolated and structurally characterized for the first time. The efficiency of this cobalt catalyst was demonstrated in the alcohol dehydrogenation and dehydrative coupling of secondary alcohols under mild conditions into ketones and ethers, respectively.

Among the best-performing homogeneous catalysts for the direct amination of activated secondary alcohols with electron-poor amine derivatives, metal triflates, such as aluminum triflate, Al(OTf)3, stand out. Herein we report the extension of this reaction to electron-rich amines and activated primary alcohols. We provide detailed insight into the structure and reactivity of the catalyst under working conditions in both nitromethane and toluene solvent, through experiment (cyclic voltammetry, conductimetry, NMR spectroscopy), and density functional theory (DFT) simulations. Competition between aniline and benzyl alcohol for Al in the two solvents explains the different reactivities. The catalyst structures predicted from the DFT calculations were validated by the experiments. Whereas a SN1-type mechanism was found to be active in nitromethane, we propose a SN2 mechanism in toluene to rationalize the much higher selectivity observed when using this solvent. Also, unlike what is commonly assumed in homogeneous catalysis, we show that different active species may be active instead of only one.

A dehydrative cross-etherification reaction of two different alcohols is achieved in the presence of hydrothermally synthesized tungsten-titanium mixed metal oxide (W-Ti-O) catalyst. The reaction is environmentally benign: organic solvent is not necessary and the catalyst is readily recovered and reusable.

The role of counterions in chemistry mediated by gold complexes stretches much further than merely providing charge balance to cationic gold species. Interplay between their basicities and coordination strengths influences interactions with both the gold center and substrates in catalysis. Actual monogold(I) active species are generally believed to be monocoordinated species, formed from the abstraction or the decoordination of a second ligand from precursor complexes, but only a small amount of experimental evidence exists to underpin the existence of these transient species. The formation of a bench-stable neutral IPrCl-gold(I) tetrafluoroborate complex is reported herein. Experimental studies by X-ray diffraction analysis and NMR spectroscopy and theoretical studies by DFT calculations were conducted to determine the composition, structure, and behavior of this complex. The absence of an auxiliary ligand resulted in inner-sphere coordination of the counterion in the solid state. In solution, an equilibrium between two conformations was found with the counterion occupying inner-sphere and outer-sphere positions, respectively. Stoichiometric and catalytic reactivity studies with the tetrafluoroborate complex have been conducted. These confirmed the lability of the inner-sphere coordinating counterion that gives the IPrCl-gold(I) fragment behavior similar to that of related systems.

Reactions of benzyl alcohols with HI in solvent-free conditions were examined. Three types of reactions (iodination, reduction, and ring formation) occurred depending on the degree of crowding around the benzyl position and the benzylic stabilization of substrates. Results also showed that the ring formation to give indanes proceeded efficiently when HI was used, and that compounds with electron-rich aromatic rings gave indane derivatives in good yields.

An iridium(iii) Cp? complex containing a triazolylidene-pyridyl C,N-bidentate-coordinating ligand is a very powerful catalyst for the transformation of ketones and aldehydes into symmetrical ethers. This highly efficient reductive coupling proceeds immediately at room temperature and at a low catalyst loading (0.1 mol%) when Ph2SiH2 is used as an additive. Aromatic carbonyl substrates react faster than aliphatic ketones or aldehydes, and the substrate scope suggests some functional group tolerance. Likewise, the condensation of alcohols to symmetrical ethers is catalyzed by this triazolylidene iridium complex, though ether formation is an order of magnitude slower than when starting from the analogous ketone or aldehyde as a substrate, suggesting that alcohols are not potential intermediates in the reductive coupling process. Prolonged reactions or modification of the silane additive lead to ether cleavage and dehydration, thus affording the corresponding olefin. Mechanistic insights and in particular the different reactivities of alcohols and ketones have been exploited to develop a synthetic methodology for the iridium-catalyzed formation of unsymmetrical methyl ethers (R-OMe) in good yields.

Iodine-catalyzed transformations of alcohols under solvent-free reaction conditions (SFRC) and under highly concentrated reaction conditions (HCRC) in the presence of various solvents were studied in order to gain insight into the behavior of the reaction intermediates under these conditions. Dimerization, dehydration and substitution were the three types of transformations observed with benzylic alcohols. Dimerization and substitution reactions were predominant in the case of primary- and secondary alcohols, whereas dehydration prevailed in the case of tertiary alcohols. The relative reactivity of substituted 1-phenylethanols in I2-catalyzed dimerization under SFRC provided a good Hammett plot ρ+ = -2.8 (r2 = 0.98), suggesting the presence of electron-deficient intermediates with a certain degree of developed charge in the rate-determining step.

Reductive coupling of various carbonyl compounds to the corresponding symmetric ethers with dimethylphenylsilane is reported using a carbon-supported dioxo-molybdenum catalyst. The catalyst is air- and moisture-stable and can be easily separated from the reaction mixture for recycling. In addition, the catalyst is chemoselective, thus enabling the synthesis of functionalized ethers without requiring sacrificial ligands or protecting groups.

The synthesis of thioethers starting from alcohols and thiols in the presence of amorphous solid acid catalysts is reported. A silica alumina catalyst with a very low content in alumina gave excellent results in terms of both activity and selectivity also under solvent-free conditions. The reaction rate follows the electron density of the carbinol atom in the substrate alcohol and yields up to 99% and can be obtained for a wide range of substrates under mild reaction conditions.

An expeditious and highly practical, microwave assisted benzylation of naphthols and 4-hydroxycoumarin has been developed under catalyst-free & solvent-free conditions. Alcohols undergo heat induced dehydration to form ethers, which collapse reversibly to form the carbocation which was captured immediately by a suitable nucleophile to furnish the benzylated compounds.

The development of new and inexpensive heterogeneous catalysts for direct C-C cross-coupling of primary and secondary alcohols is a challenging goal and has great importance in academic and industrial sectors. In this work Cu-Ag/hydrotalcite (Cu-Ag/HT) catalysts were prepared and tested for their impact on this cross-coupling. The effect of supports, including MgO, γ-Al2O3 and HT with different Mg : Al molar ratios, was investigated. It was found that the acidic or basic properties of the supports affected product selectivity. The roles of Cu and Ag sites in the cross-coupling were also investigated with the prepared Cu-Ag/HT catalyst demonstrating high activity and selectivity for the reaction. The yield-to-target product of β-phenylpropiophenone reached 99% after 1 h under optimum reaction conditions. The stability in air and reusability studies show that Cu-Ag/HT can be stored for 6 days and can be used five times without apparent deactivation, respectively.

Despite the rapid development of frustrated Lewis pair (FLP) chemistry over the last ten years, its application in catalytic hydrogenations remains dependent on a narrow family of structurally similar early main-group Lewis acids (LAs), inevitably placing limitations on reactivity, sensitivity and substrate scope. Herein we describe the FLP-mediated H2activation and catalytic hydrogenation activity of the alternative LA iPr3SnOTf, which acts as a surrogate for the trialkylstannylium ion iPr3Sn+, and is rapidly and easily prepared from simple, inexpensive starting materials. This highly thermally robust LA is found to be competent in the hydrogenation of a number of different unsaturated functional groups (which is unique to date for main-group FLP LAs not based on boron), and also displays a remarkable tolerance to moisture.

A cosolvent-promoted O-benzylation strategy with Ag2O was developed. The cosolvent consisting of CH2Cl2 and n-hexane can not only improve the reaction solubility for carbohydrates but also increase the benzylation efficiency. The formation of byproducts is greatly inhibited in the developed method. This method is simple, mild, and highly effective, and numerous 1′-benzylated sucrose derivatives were prepared including a photoreactive (trifluoromethyl)phenyldiazirine-based sucrose. The mechanisms of benzylation with primary and secondary benzyl bromides were also elaborated. Furthermore, the application scope with alcohols, glucose, and ribose derivatives was investigated.

A chemoselective method for the direct halogenation of different types of alcohols with halosilanes under catalyst- and solvent-free reaction conditions (SFRC) is reported. Various primary, secondary and tertiary benzyl alcohols and tertiary alkyl alcohols were directly transformed to the corresponding benzyl and alkyl halides, respectively, using chlorotrimethylsilane (TMSCl) and bromotrimethylsilane (TMSBr).

Three new complexes bearing a chelating (κ2C,O) NHC-SO3 ligand have been prepared. An original method for the synthesis of the imidazolium-sulfonate NHC precursor is described. The 5-membered ruthena- and irida-cycle containing complexes were fully characterized and evaluated in a series of catalytic transformations involving hydrogen auto-transfer processes.

The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote SN1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.

Thiazolium and imidazolium hybrid materials were prepared by radical reactions between a mercaptopropyl-modified SBA-15 mesoporous silica and bis-vinylthiazolium or bis-vinylimidazolium dibromide salts. These hybrid materials were characterized by several techniques and were employed in the etherification reaction of 1-phenylethanol. Solvent-free conditions at 160C under different gas phases (oxygen, air, nitrogen and argon) were used. The thiazolium-based material displayed excellent performances. Further studies were carried out using unsupported thiazolium salts, with or without a methyl group at the C-2 position of the thiazolium moiety. These studies allowed us to propose a reaction mechanism. The supported thiazolium-based material was successfully used in the etherification reaction of two other benzylic alcohols and also in seven consecutive cycles. This work represents the first use of thiazolium-based compounds as catalysts for the etherification reaction of alcohols.

Organohalides are found to be effective catalysts for dehydrative O-alkylation reactions between alcohols, providing selective, practical, green, and easily scalable homo- and cross-etherification methods for the preparation of useful symmetrical and unsymmetrical aliphatic ethers from the readily available alcohols. Mechanistic studies revealed that organohalides are regenerated as reactive intermediates and recycled to catalyze the reactions.

Mesoporous Mn-Zr composite oxides (M-MnZr) with a crystalline wall were designed and achieved by a facile one-pot evaporation-induced self-assembly (EISA) strategy. As proved by XRD, HRTEM and SAED characterization, the wall of the obtained mesoporous materials exhibited a typical tetragonal phase of ZrO2. In addition, the introduced manganese species were homogeneously dispersed in the mesoporous skeleton. N2-physisorption and TEM results showed that all the final materials possessed an obvious mesoporous structure accompanied by a large specific surface area (～120 m2 g-1), big pore volume (～0.2 cm3 g-1) and uniform pore size (～4.9 nm). In addition, the liquid phase oxidation was chosen as the test reaction and the excellent catalytic performance of M-MnZr demonstrated their potential applications in oxidation reactions. This journal is

A series of ordered mesoporous transition metal-zirconium oxophosphate composites (M-X-ZrPO, X = Cr, Mn, Fe, Co, Ni, Cu, Zn) were designed and synthesized via a facile and general one-pot evaporation-induced self-assembly (EISA) method. N2-physisorption and TEM characterization showed that all the final materials possessed ordered mesoporous structure accompanied by large specific surface area (170-220 m2 g-1), big pore volume (0.2-0.4 cm3 g-1) and uniform pore size (5.6-7.8 nm). Moreover, the introduced transition metals homogeneously dispersed in the mesoporous skeleton and effectively improved the mesostructure. The catalytic performance of M-X-ZrPO was evaluated in the liquid phase oxidation of ethylbenzene. The introduced transition metals obviously enhanced the catalytic performance of M-ZrPO. M-Mn-ZrPO showed excellent catalytic activity with 91.6% conversion of ethylbenzene and 87.0% selectivity of acetophenone. After five cycles, there was no notable decrease in catalytic activity. Therefore, it was a promising catalyst for the oxidation of ethylbenzene.

Sec-Benzyl azides were efficiently prepared by bismuth(III)-catalyzed direct azidation of sec-benzyl alcohols. The reaction was applied to a variety of substrates to provide the desired products in up to 99% yield within a short reaction time.

The effect of the addition of ILs with non-coordinating anions on the iron-catalyzed benzylation of 1,3-dicarbonyl compounds with alcohols under solvent free conditions has been evaluated. Among them, the presence of those containing the bistriflimide anion was found to be crucial for selectivity towards the benzylated product in a homogenous reaction. Therefore, the catalytic activity of Fe(OTf)3-N4111NTf2 combination supported on carbon materials with different textural and chemical surface properties has been studied. In the heterogeneous phase, reaction selectivity was also enhanced by the addition of the IL. However, substantial differences between the activities of different Fe-IL/carbon material catalytic systems were observed, indicating the influence of carbon support properties. With regards to selectivity, the best results were obtained using carbon supports with low microporosity. Moreover, the presence of oxygen functional groups on the carbon surface improved catalyst recycling. the Partner Organisations 2014.

A homogeneous catalytic system consisting of Mn(ii) acetate (18 μmol), tert-butylhydroperoxide (2.5 mmol), acetonitrile (1.5 mL) and trifluoroacetic acid (91 μmol) was developed for efficient and selective oxidation of various alcohols (1 mmol). The system yielded good to quantitative conversions (42-100%) of various secondary alcohols, such as 2-octanol, fenchyl alcohol and borneol, to their corresponding ketones. Primary alcohols, for example 1-octanol and differently substituted benzyl alcohols, were mainly converted to their corresponding carboxylic acids. Studies with a selection of hydrocarbons, tertiary amines and a cyclic ether isochroman showed that besides alcohols, other substrates can be oxidised as well.

Friedel-Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di- and triarylmethanes. We have established an efficient iron-catalyzed Friedel-Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron-catalyzed self-condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono-benzylated arene (diand tri-arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis-benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel-Crafts benzylations hardly proceed.

A series of [MoO2(acac′)2] [acac′ = acetylacetonato-type ligand: dibenzoylmethane (3), 1-benzoylacetone (4), bis(p-methoxybenzoyl)methane (5), 2-acetylcyclopentanone (6), 2-acetylcyclohexanone (7), and 2-acetyl-1-tetralone (8)] complexes have been synthesized in yields of 44-83 % by a simple synthetic method by using sodium molybdate and the desired acac-type ligand as starting materials. All the complexes were characterized by IR, UV/Vis, NMR, and high-resolution ESI-MS, and for compounds 3, 4, and 8, solid-state structures were obtained by X-ray diffraction. All the complexes contain a cis-dioxomolybdenum moiety, as proven by the characteristic Mo=O vibrations in the IR spectra and the occurrence of four sets of signals in the NMR spectra of the complexes bearing asymmetrical ligands (4 and 6-8), and confirmed by the solid-state structures. The complexes were found to be active as catalysts in the dehydration of 1-phenylethanol to styrene using technical-grade toluene as the solvent in air at 100 °C. The highest catalytic activity was found for [MoO2{(tBuCO) 2CH}2] (2), followed by [MoO2{(C 6H5CO)2CH}2] (3). Both complexes were also found to be active in the dehydration of other alcohols, including allylic, aliphatic, and homoallylic alcohols, as well as secondary and tertiary alcohols, with 2 generally showing better activity and selectivity than 3. These catalytic results were compared with those previously obtained with the metal-based catalyst Re2O7 and the benchmark acid catalyst H2SO4. The results were dependent on the substrate: By using 2, good selectivities but lower activities were generally obtained with tertiary alcohols, whereas good activities but lower selectivities were obtained with secondary alcohols. The industrially important dehydration of 2-octanol to octenes was very efficiently catalyzed by 2. Overall, the [MoO 2(acac′)2] complexes reported herein could offer a cheaper and more abundant metal-based catalyst alternative to the previously reported rhenium-based catalytic system for the dehydration reaction. Copyright

Aggregates of zeolite nanoparticles were linked together with polypropylene oxide or polydimethylsiloxane polymer chains, and were used as catalysts for liquid-phase reactions. The polymer-linked catalysts showed high catalytic activity in esterification of acetic acid with 1-propanol and hydrolysis of ethyl acetate, and were readily separated from reaction mixtures by decantation. Moreover, the linkage with the polymer chains enhanced shape selectivity in esterification of acetic acid with cyclohexanol and dehydration of 1-phenylethanol because of passivating the external acid sites of the zeolite with the polymer.

Mesoporous nickel aluminosilicate, a solid acid catalyst prepared by sol-gel technique was utilized as a heterogeneous catalyst for the synthesis of symmetrical ethers by dehydro-condensation of alcohols. The prepared catalysts were characterized by Fourier-transform infra red spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), N2 adsorption-desorption analysis, temperature programmed desorption of ammonia (TPD) and X-ray photoelectron spectroscopic techniques. The presence of the catalyst assisted the etherification reaction in 30 minutes. Ethers formed in these reactions were quantified by gas chromatography (GC) and the identities of few of them were confirmed by nuclear magnetic resonance spectral data (NMR). Copyright

In this study, we investigate the effect of the electrophiles and the nucleophiles for eight catalysts in the catalytic SN1 type substitution of alcohols with different degree of activation by sulfur-, carbon-, oxygen-, and nitrogen-centered nucleophiles. The catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols and follow the trend of alcohol reactivity. However, when it comes to the nucleophile, the eight catalysts show general and specific variances in the efficiency and selectivity to perform the desired substitution. Interestingly, the selectivity of the alcohols to produce the desired substitution products was found to be independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation. Catalysts based on iron(III), bismuth(III), and gold(III) show higher conversions for S-, C-, and N-centered nucleophiles, and BiIII was the most efficient catalyst in all combinations. Catalysts based on rhenium(I) or rhenium(VII), palladium(II), and lanthanum(III) were the most efficient in performing the nucleophilic substitution on the various alcohols with the O-centered nucleophiles. These catalysts generate the symmetrical ether as a by-product from the reactions of S-, C-, and N-centered nucleophiles as well, resulting in lower chemoselectivity. Who's the boss? In a comprehensive study of catalytic S N1 type direct substitution of alcohols, the catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols but are highly variable with respect to the nucleophiles. The reactivity of the alcohols is independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation.

Nanostructured V2O5 was prepared by electrochemical anodization in the presence of complex fluoride electrolytes. The reactivity of nanostructured V2O5 was compared to a commercially available V2O5 sample in several oxidation reactions. Catalyst nanostructuring offers improvements in yields as well as rate enhancement in oxidations.

A new bifunctional Br?nsted acid catalyst that contains two sulfo groups was prepared. The adsorption of this new bifunctional Br?nsted acid catalyst on silica gel made it possible to be reused 10 times without a loss of catalytic activity in the solvent-free esterification of bromoacetic acid with an equiv. of benzyl alcohol without the formation of dibenzyl ether.

Disclosed is a method for the transition metal-mediated oxidation of C-H bonds to form C-0 or C-S bonds. The methods are useful for the formation of ethers (R-OR') from alcohols, R'OH, and sp3 -hybridized C-H bonds in substrates, R-H. Aryl or heteroaryl acetates may also be used for C-H to C-OAr bond formation. The methods are also useful in the preparation of C-S bonds from acetyl-protected thiols, MeC(0)SR, and disulfides, RSSR. Advantageously, the methods minimize reaction steps, the handling of oxidized intermediates, and environmental impact.

Chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenyl ethanol into R-1-phenylethanol acetate was investigated with emphasis on the minimization of side reactions. The organometallic hydrogen transfer (racemization) catalyst was varied, and this

Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase without any solvent with carbon-based solid acid catalysts prepared in one step from renewable resources like d-glucose for the first time. The carbon-based catalyst shows

Azidation: Siloxy groups derived from secondary and tertiary benzyl alcohols can be transformed into azide groups at room temperature using TMSN3 in the presence of an iron catalyst (see scheme; TMS=trimethylsilyl). Secondary and tertiary benzy

A protocol is described for the reduction of carboxylic acids to primary alcohols using 1,1,3,3-tetramethyldisiloxane (TMDS) and a catalytic amount of Cu(OTf)2. Aliphatic as well as aromatic carboxylic acids are reduced in high selectivity and good yields. TMDS/Cu(OTf)2 has also been found to be an efficient catalytic reducing system for the preparation of symmetrical ethers from carbonyl compounds under mild conditions.

Straightforward etherification of benzyl alcohols (1) via intermolecular dehydration can be efficiently catalyzed by sodium bisulfite under solvent-free conditions. In the presence of 0.3 mol% or 0.6 mol% amount of sodium bisulfite, symmetric and unsymmetric ethers are prepared from the corresponding alcohols in high yields (up to 95%). Etherification of benzhydryl alcohols is also discussed. Copyright