Efficient and solvent-free synthesis of bis-indolylmethanes using silica gel supported aluminium chloride as a reusable catalyst

Stable and non-hygroscopic silica gel supported aluminium chloride（SiO₂-AlCl₃）,which is prepared easily from cheap and commercially available compounds was found to be an environmentally friendly heterogeneous catalyst for the condensation of indole with aldehydes and ketones to afford bis-indolylmethanes at room temperature under solvent-free conditions.The catalyst can be reused up to five times after simple washing with ether.     

Selective tetrahydropyranylation of alcohols and phenols using titanium(IV) salophen trifluoromethanesulfonate as an efficient catalyst

Titanium(IV) salophen trifluoromethanesulfonate, [Ti^IV(salophen)(OSO₂CF₃)₂], as a catalyst enables selective tetrahydropyranylation of alcohols and phenols with 3,4‐dihydro‐2H‐pyran. Using this catalytic system, primary, secondary and tertiary alcohols, as well as phenols, were converted to their corresponding tetrahydropyranyl ethers in high yields and short reaction times at room temperature. Investigation of the chemoselectivity of this method showed discrimination between the activity of primary alcohols in the presence of secondary and tertiary alcohols and phenols. This heterogenized catalyst could be reused several times without loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Polymer-supported gadolinium triflate as a convenient and efficient Lewis acid catalyst for acetylation of alcohols and phenols

A polymer-supported gadolinium triflate (CMPS-IM-Gd) catalyst was prepared from chloromethyl polystyrene (CMPS) resin using a simple and convenient procedure. This polymeric catalyst was used as an efficient Lewis acid catalyst for the acetylation of various alcohols and phenols with acetic anhydride, affording high yields under mild conditions. The reaction was completed in a short period of time with small amounts of the catalyst. The catalyst was reused over 10 times without any significant loss of its catalytic activity.     

Copper methanesulfonate-acetic acid as a novel catalytic system for tetrahydropyranylation of alcohols and phenols

A synergistic catalytic effect between copper methanesulfonate and acetic acid in tetrahydropyranylation of alcohols and phenol at room temperature under solvent free condition has been described. Both alcohols (primary, secondary and tertiary) and phenols reacted with 3,4-dihydro-2H-pyran smoothly to afford the corresponding tetrahydropyranyl ethers in good yields.     

Efficient and green tetrahydropyranylation and deprotection of alcohols and phenols by using activated carbon supported sulfuric acid

A simple, green and efficient method for the DHP protection of various alcohols and phenols and the subsequent removal of the corresponding protective group in the presence of a catalytic amount of the activated carbon supported H2SO4 is described.     

Cross‐linked poly(4‐vinylpyridine/styrene) copolymer‐supported bismuth(III) triflate: an efficient heterogeneous catalyst for silylation of alcohols and phenols with HMDS

Cross‐linked poly(4‐vinylpyridine/styrene) copolymer‐supported bismuth(III) triflate (³⁰P/S‐Bi) effectively activates hexamethyldisilazane (HMDS) for the silylation of alcohols and phenols. By the use of this heterogeneous catalytic system, a wide range of alcohols as well as phenols are converted into their corresponding trimethylsilyl ethers in high yield under mild reaction conditions. The catalyst was reused more than 10 times without significant loss of its catalytic activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Gal3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

In dichloromethane, the nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP) was catalyzed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine to give the corresponding tetrahydropyranyl acetals in good to excellent yields.     

Safe radical azidonation using polystyrene supported diazidoiodate(I)

Aldehydes are converted to acyl azides and benzyl ethers to azido ethers by treatment with polymer supported iodine azide in MeCN at 83 °C. The reaction provides a safe and convenient alternative to the use of iodine azide in radical azidonations.     

Air-stable titanocene bis(perfluorooctanesulfonate) as a new catalyst for acylation of alcohols, phenols, thiols, and amines under solvent-free condition

Air-stable titanocene bis(perfluorooctanesulfonate) [Cp₂Ti(OSO₂C₈F₁₇)₂] that shows high Lewis acidity was prepared from Cp₂TiCl₂ and AgOSO₂C₈F₁₇. The compound was characterized by different techniques, and examined as a catalyst for acylation reactions. It was found that using equimolar acetic anhydride as acetylating agent and under solvent-free condition, Cp₂Ti(OSO₂C₈F₁₇)₂ exhibits high activity and selectivity in the acetylation of various alcohols, phenols, thiols, and amines. Also, good catalytic efficiency is observed in the acylation of 2-phenylethanol across various acylating reagents. The catalyst can be reused without loss of activity in a test of ten cycles. The Cp₂Ti(OSO₂C₈F₁₇)₂ catalyst affords a simple, efficient and general method for the acylation of alcohols, phenols, thiols, and amines.     

Cupric sulfate pentahydrate (CuSO4·5H2O): a mild and efficient catalyst for tetrahydropyranylation/depyranylation of alcohols and phenols

Various alcohols and phenols can be smoothly converted to the corresponding THP ethers using 20 mol % CuSO₄·5H₂O under mild reaction conditions at room temperature. Some of the major advantages of this procedure are nonaqueous work-up, very good yields, less expensive catalyst and compatibility with other protecting groups.     

Niobium(V) chloride: an efficient catalyst for selective acetylation of alcohols and phenols

Acetylation of various alcohols, were carryout successfully, while using acetic anhydride and catalytic amount of niobium(V) chloride at room temperature. The method is very mild towards other functional groups and the yields were in excellent.     

NaCl担载Fe催化裂解乙炔制备纳米碳材料

以水溶性NaCl担载Fe作催化剂,于400℃和420C下化学气相沉积法催化裂解乙炔进行了反应.通过X射线衍射仪、扫描电子显微镜和能谱分析仪对催化剂进行了表征,表征结果显示:活性组分Fe被分散成了粒径在10～40nm之间的纳米颗粒;通过扫描电子显微镜和高分辨透射电镜对产物进行了表征,表征结果显示:当裂解温度为400℃时,...     

A fast procedure for the preparation of vicinal azidoalcohols using polymer supported reagents

Several vicinal azidoalcohols were prepared in good to high yield and purity, starting from aryl α-haloketones, using reagents supported on a macroporous ion exchange resin. This is a fast and new approach to aryl azidoalcohols.     

3,5-Dinitrobenzoic acid catalyzed synthesis of 2,3-unsaturated O- and S-glycosides and tetrahydropyranylation of alcohols and phenols

A simple procedure for the synthesis of 2,3-unsaturated glycosides in acetonitrile and tetrahydropyranylation of alcohols and phenols in dichloromethane in the presence of 3,5-dinitrobenzoic acid is described. A variety of alcohols and thiols are reacted with glycals to give the desired products in high yields with high α-selectivity.     

Microwave-assisted preparation of dialkylimidazolium tetrachloroaluminates and their use as catalysts in the solvent-free tetrahydropyranylation of alcohols and phenols

Microwave-assisted preparation of dialkylimidazolium tetrachloroaluminates, [CnMIM][AlCl4] and their application as recyclable catalysts for the efficient and eco-friendly protection of alcohols as tetrahydropyranyl (THP) ethers are described. The same catalyst can also be utilized for the deprotection of THP ethers.     

Mechanistic comparison of aluminium based catalysts for asymmetric cyanohydrin synthesis

A kinetic analysis of the asymmetric addition of trimethylsilyl cyanide to benzaldehyde using three aluminium based catalysts has been carried out. All three catalysts displayed rate equations, which were first order in trimethylsilyl cyanide concentration and zero order in benzaldehyde concentration. The results are consistent with a common mechanism for effective asymmetric catalysis of cyanohydrin synthesis, involving combined activation of the aldehyde by a Lewis acid and activation of the trimethylsilyl cyanide by a Lewis base. The mechanistic analysis was also applied to a magnesium-based catalyst system to demonstrate its general applicability.     

Cellulose hydrolysis using zinc chloride as a solvent and catalyst

Cellulose gel with < 10% of crystallinity was prepared by treatment of microcrystalline cellulose, Avicel, with zinc chloride solution at a ratio of zinc chloride to cellulose from 1.5 to 18 (w/w). The presence of zinc ions in the cellulose gels enhanced the rate of hydrolysis and glucose yield. The evidence obtained from X-ray diffraction, iodine absorption experiments; and Nuclear Magnetic Resonance spectra analysis suggested the presence of zinc-cellulose complex after Avicel was treated with zinc chloride. Zinc-cellulose complex was more susceptible to hydrolysis than amorphous cellulose. Under the experimental condition, cellulose gels with zinc ions were hyrolyzed to glucose with 95% theoretical yield and a concentration of 14% (w/v) by cellulases within 20 h. The same gel was hydrolyzed by acid to glucose with 91.5% yield and a concentration of 13.4% (w/v).     

Direct N-alkylation of amines with alcohols using AlCl3 as a Lewis acid

A substitution reaction of amines with alcohols for N-alkylated amines has been developed using inexpensive AlCl_3 without any ligand or additive.Either aromatic or aliphatic amines and primary or secondary alcohols perform the AlCl_3-mediated reaction smoothly to afford various N-alkylated amines in satisfactory yields.     

聚氯乙烯支载三氯化铁试剂催化醛与乙酸酐反应合成 乙酰缩醛

聚氯乙烯支载三氯化铁(PVC-FeCl3)试剂在室温条件下能方便快速催化各类醛与乙酸酐反应,以良好产率(75%～96%)生成相应乙酰缩醛。     

Efficient tetrahydropyranyl and tetrahydrofuranyl protection/deprotection of alcohols and phenols with Al(OTf)3 as catalyst

A simple and efficient method for the conversion of alcohols and phenols into their corresponding THP and THF ethers at room temperature has been developed using 1 mol % aluminium triflate as catalyst. The deprotection reaction in the presence of methanol using Al(OTf)₃ was equally successful and could be performed at ambient temperature in high yields.