Polystyrene‐Gallium Trichloride Complex: A Mild,Highly Efficient,and Recyclable Polymeric Lewis Acid Catalyst for Chemoselective Silylation of Alcohols and Phenols with Hexamethyldisilazane

Polystyrene‐supported gallium trichloride (PS/GaCl₃) as a highly active and reusable heterogeneous Lewis acid effectively activates hexamethyldisilazane (HMDS) for the efficient silylation of alcohols and phenols at room temperature. In this heterogeneous catalytic system, primary, secondary, and tertiary alcohols as well as phenols were converted to their corresponding trimethylsilyl ethers with short reaction times and high yields under mild reaction conditions. The heterogenized catalyst is of high reusability and stability in the silylation reactions and was recovered several times with negligible loss in its activity or a negligible catalyst leaching, and also there is no need for regeneration. It is noteworthy that this method can be used for chemoselective silylation of different alcohols and phenols with high yields.     

Electron-deficient [Ti(salophen)(OTf)2]: A new and highly efficient catalyst for the acetylation of alcohols and phenols with acetic anhydride

In the present work, a highly efficient method for acetylation of alcohols and phenols with acetic anhydride catalyzed by high-valent [Ti^IV(salophen)(OTf)₂] is reported. Under these conditions, primary, secondary and tertiary alcohols as well as phenols were acetylated with short reaction times and high yields. The catalyst was reused several times without loss of its catalytic activity.     

Zirconyl triflate: A new, highly efficient and reusable catalyst for acetylation and benzoylation of alcohols, phenols, amines and thiols with acetic and benzoic anhydrides

Highly efficient acetylation and benzoylation of alcohols, phenols, amines and thiols with acetic and benzoic anhydrides catalyzed by new and reusable zirconyl triflate, ZrO(OTf)₂, is reported. The high catalytic activity of electron deficient ZrO(OTf)₂ can be used for the acetylation and benzoylation of not only primary alcohols but also sterically-hindered secondary and tertiary alcohols with acetic and benzoic anhydrides. Acetylation of phenols with acetic and benzoic anhydrides was achieved to afford the desired acetates and benzoates efficiently. This catalyst also efficiently catalyzed the acetylation and benzoylation of amines and thiols whereby the corresponding amides and thioesters were obtained in good to excellent yields. This catalyst can be reused several times without loss of its activity.     

Ni/Silica catalyzed acetylation of phenols and naphthols: An eco-friendly approach

A method for 10% Ni/SiO₂ catalyst is developed for acetylation of phenol, substituted phenols, naphthols, substituted alcohols under mild liquid phase conditions affording aromatic esters with maximum conversions of 50–80% and 100% selectivity. The catalyst showed remarkable reusability for up to 4 cycles. This methodology is eco-friendly, economic with Ni/SiO₂ catalysts exhibiting no loss of activity the first report for acetylation of substituted phenols to esters with 10% Ni/SiO₂ catalyst.     

Molecular iodine in isopropenyl acetate (IPA): a highly efficient catalyst for the acetylation of alcohols, amines and phenols under solvent free conditions

Iodine in isopropenyl acetate (IPA) is a highly efficient catalyst for the acetylation of a variety of alcohols, phenols and amines under solvent free conditions. Primary, secondary, tertiary alcohols, amines and mono to polyhydroxy phenols and anilines with electron donating or withdrawing substituents can be easily acetylated in good to excellent yield at 85-90 °C.     

Highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron-deficient [Ti(salophen)(OTf)2]

In the present work, highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by high-valent [Ti^IV(salophen)(OTf)₂] is reported. Under these conditions, primary, secondary and tertiary alcohols as well as phenols were silylated in short reaction times and high yields. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.     

Polystyrene-bound electron-deficient tin(IV) porphyrin: A new, highly efficient, robust and reusable catalyst for acetylation of alcohols and phenols with acetic anhydride

In the present work, tetrakis(p-aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], supported on chloromethylated polystyrene was prepared and characterized by elemental analysis, FT IR and diffuse reflectance UV-Vis spectroscopic methods. This new heterogenized catalyst was used for acetylation of alcohols and phenols with acetic anhydride in short reaction times and high yields. The catalyst is of high reusability and stability in the acetylation reactions and was recovered several times without loss of its initial activity and catalyst leaching.     

RAPID AND EFFICIENT ACETYLATION OF ALCOHOLS AND PHENOLS WITH ACETIC ANHYDRIDE USING TIN(IV) PORPHYRIN AS CATALYST

ABSTRACT

The efficient and rapid esterification of alcohols and phenols in acetic anhydride was achieved by tin(IV) tetraphenylporphyrin perchlorate [Sn^IV (tpp) (ClO₄)₂] as catalyst in high yields. Sn^IV (tpp) (ClO₄)₂ showed highly catalytic activity on the acetylation reaction.     

N,N ′-Diiodo-N,N′-1,2-ethanediylbis(p-toluenesulfonamide) as an Efficient Catalyst for Acetylation of Alcohols,Phenols, Amines,and Thiols Under Solvent-Free Conditions

N,N′-Diiodo-N,N′-1,2-ethanediylbis(p-toluenesulfonamide) (NIBTS) is a highly efficient catalyst for the acetylation of alcohols, phenols, amines, and thiols under solvent-free conditions. Primary, secondary, tertiary alcohols; phenols; amines; and thiols can be easily acetylated in good to excellent yields at 80 °C.     

Rapid,highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron‐deficient tin(IV)porphyrin

In this paper, rapid and highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of high‐valent [Sn^IV(TPP)(OTf)₂] is reported. This catalytic system catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS‐ethers were obtained in high yields and short reaction times at room temperature. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity. Copyright © 2009 John Wiley & Sons, Ltd.     

ZnAl2O4 SiO2纳米复合催化剂用于无溶剂条件下乙酸酐与醇、酚和胺的乙酰化反应简

A ZnAl₂O₄@SiO₂ nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N₂ adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl₂O₄@SiO₂ nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH₂ group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl₂O₄@SiO₂ nanocomposite was higher than that of pure ZnAl₂O₄. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis.     

Efficient Acetylation of Alcohols,Phenols, and Amines Catalyzed by Melamine Trisulfonic Acid (MTSA)

Melamine trisulfonic acid (MTSA) was easily prepared by the reaction of melamine with neat chlorosulfonic acid at room temperature. This reagent can be used as an efficient catalyst for the acetylation of alcohols, phenols, and amines with Ac₂O under mild and completely heterogeneous reaction conditions.     

Highly efficient tetrahydropyranylation of alcohols and phenols catalyzed by a new and reusable high-valent vanadium(IV) porphyrin

In the present work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V^IV(TPP)(OTf)₂], in the tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) is reported. This new electron-deficient V(IV) compound was used as a highly efficient catalyst for pyranylation of primary (aliphatic and benzylic), sterically-hindered secondary and tertiary alcohols with DHP. Tetrahydropyranylation of phenols with DHP was also performed to afford the desired THP-ethers. The chemoselectivity of this method was also investigated. The results indicated that primary alcohols are more reactive in the presence of secondary and tertiary alcohols and phenols. This catalyst was reused several times without loss of its activity.     

Preparation,characterization and application of RHA/TiO2 nanocomposites in the acetylation of alcohols,phenols and amines

In this work, anatase-phase nano-titania was prepared by embedding in rice husk ash, and identified using a variety of techniques. The obtained nanocomposite (RHA/TiO₂) was used as a green and inexpensive catalyst for the promotion of the acetylation of alcohols, phenols and amines with Ac₂O at room temperature under solvent free conditions. The procedure gave the products in excellent yields during all reaction times. Also this catalyst can be reused for several times without loss of its catalytic activity.     

A novel 3-nitrobenzeneboronic acid as an extremely mild and environmentally benign catalyst for the acetylation of alcohols under solvent-free conditions

A novel 3-nitrobenzeneboronic acid is found to catalyse efficiently the acetylation of a wide range of alcohols as well as phenols with acetic anhydride in good to excellent yields at room temperature under solvent-free conditions. The reactions are clean and the catalyst is mild such that highly sensitive functional groups including oximes are stable to the reaction conditions.     

Rice husk: Introduction of a green,cheap and reusable catalyst for the protection of alcohols,phenols, amines and thiols

A mild, efficient and eco-friendly protocol for the chemoselective protection of benzylic and primary and less hindered secondary aliphatic alcohols and phenols as trimethylsilyl ethers and different types of amines as N-tert-butylcarbamates is developed using rice husk (RiH) as the catalyst. This reagent is also able to catalyze the acetylation of alcohols, phenols, thiols and amines with acetic anhydride. Easy work-up, relatively short reaction times, excellent yields and low cost, availability and reusability of the catalyst are the striking features of this methodology, which can be considered to be one of the best and general methods for the protection of alcohols, phenols, thiols and amines. In addition, the use of a green reagent in the above-mentioned reactions results in a reduction of environmental pollution and of the cost of the applied methods.     

[Sn(TPP)(BF4)2]: An efficient and reusable catalyst for chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane

Tin(IV)tetraphenylporphyrinato tetrafluoroborate, [Sn^IV(TPP)(BF₄)₂], was used as an efficient catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS). High-valent [Sn^IV(TPP)(BF₄)₂] catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS-ethers were obtained in high yields and short reaction times at room temperature. While, under the same reaction conditions [Sn^IV(TPP)Cl₂] is less efficient to catalyze these reactions. One important feature of this catalyst is its ability in the chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.     

Chloroferrate(III) Ionic Liquid as Recyclable Catalyst for the Acetylation of Alcohols and Phenols and for 1,1‐Diacylation of Aldehydes

A Lewis acidic ionic liquid, [bmim][FeCl₄], was employed to catalyze acetylation of alcohols and phenols, and the conversion of aldehydes to corresponding 1,1‐diacetates without conventional organic solvents. The catalyst is easily available, water‐tolerant, recoverable and easy to handle.     

Simple and Efficient Method for Acetylation of Alcohols,Phenols, Amines,and Thiols Using Anhydrous NiCl2 Under Solvent-Free Conditions

Solvent-free acetylation of alcohols, phenols, amines, and thiols with acetic anhydride (Ac₂O) in the presence of 0.1 mol% (13 mg) anhydrous NiCl₂, an inexpensive and easily available catalyst, is described. Excellent yields, short reaction time, and mild reaction conditions are important features of this method.     

Graphene oxide‐bound electron‐deficient tin(IV) porphyrin: a highly efficient and selective catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane

The catalytic activity of graphene oxide‐bound tetrakis(p ‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) is reported. The prepared catalyst was characterized using inductively coupled plasma analysis, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared and diffuse reflectance UV–visible spectroscopies. This heterogeneous catalyst was used for selective trimethylsilylation of various alcohols and phenols with HMDS in short reaction times and high yields. Also, the catalyst is of high reusability and stability, in that it was recovered several times without loss of its initial activity. The chemoselectivity of this catalytic system in the silylation of primary alcohols in the presence of secondary and tertiary alcohols and also phenols was investigated.