Novel and chemoselective one-pot synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones starting from benzyl alcohols promoted by [(C14H24N4)2W10O32]-[bmim]NO3

Abstract  

A new and practical promoter system for one-pot, efficient, chemoselective synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones using [(C₁₄H₂₄N₄)₂W₁₀O₃₂]-[bmim]NO₃ under solvent-free conditions is described. The present work opens up a new and ecofriendly synthetic route to Erlenmeyer–Pl?chl adducts from primary benzyl alcohols in a one-pot operation.     

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, [ZrO(OTf)2], as a new and highly efficient catalyst for ring-opening of epoxides

A highly efficient method for the ring opening of epoxides catalyzed by ZrO(OTf)₂ was adopted. This catalyst efficiently catalyzed alcoholysis, acetolysis and hydrolysis of epoxides and the corresponding alkoxy alcohols, acetoxy alcohols and 1,2- diols were obtained in excellent yields. Conversion of epoxides to 1,2-diacetetes, thiiranes and 1,3-dioxolanes was also performed in the presence of catalytic amounts of ZrO(OTf)₂, and the corresponding products were obtained in high to excellent yields. The high catalytic activity of ZrO(OTf)₂ is due to the replacement of Cl with OTf, which makes the ZrO(OTf)₂ as efficient Lewis acid.     

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.     

Sonocatalytic oxidation of olefins catalyzed by heteropolyanion–montmorillonite nanocomposite

A Keggin-type heteropolyanion compound (HPO) was doped within the montmorillonite (MMT) structure by impregnation method. The synthesized catalyst was characterized by FT-IR, XRD, UV–vis, CV, SEM and elemental analysis. Based on chemical adsorption between HPO, and hydroxyl surface groups, HPOs nanoparticles were successfully located on the MMT. Moreover, the obtained nanocomposite was found as an efficient catalyst for oxidation of hydrocarbons under reflux and ultrasonic irradiation conditions.     

Hydrocarbon oxidation catalyzed by vanadium polyoxometalate supported on mesoporous MCM-41 under ultrasonic irradiation

Vanadium polyoxometalate (PVMo) supported on mesoporous MCM-41, MCM-41-NH(2), as efficient and heterogeneous catalysts, with large surface area, for hydrocarbon oxidation with hydrogen peroxide is reported. Oxidation of the alkenes and alkanes gave product selectivities, which are similar to those observed for corresponding homogeneous catalyst. PVMo-MCM was prepared by introduction of PVMo into the mesoporous molecule sieves of MCM-41 by impregnation and adsorption techniques. The samples were characterized by X-ray diffraction (XRD), thermal gravimetric-differential thermal analysis (TG-DTA), FT-IR, scanning electron microscopy (SEM), UV-Vis and cyclic voltametry (CV). Ultrasonic irradiation has a particular effect on MCM-41 structural uniformity and reduced the reaction times and improved the product yields. In addition, the solid catalysts could be recovered and reused several times without loss of its activity.     

Oxidation of alcohols with sodium periodate catalyzed by supported Mn(III) porphyrins

The mild and efficient oxidation of alcohols with sodium periodate catalyzed by manganese(III) tetrakis(p-sulfonatophenylporphyrinato) acetate, [Mn(TPPS)], supported on polyvinylpyridine, [Mn(TPPS)-PVP], and Amberlite IRA-400, [Mn (TPPS)-Ad IRA-400], at room temperature is reported. The catalysts used in this study showed high activity not only in the oxidation of benzylic and linear alcohols but also in the oxidation of secondary alcohols at room temperature. These catalysts can be reused several times without significant loss of their activity.     

Silica sulfuric acid catalyzed synthesis of benzoxazoles,benzimidazoles and oxazolo[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridines under heterogeneous and solvent-free conditions

A simple, rapid and efficient method for the preparation of benzoxazoles, benzimidazoles and oxazolo[4,5-b]pyridines from the reaction of orthoesters with o-aminophenols, o-phenylenediamine and 2-amino-3-hydroxypyridine in the presence of silica sulfuric acid under heterogeneous and solvent-free conditions is reported. The significant features of this method are short reaction times, high yields of the products, mild reaction conditions, solvent free reaction, cheapness, non-toxicity and reusability of the catalyst.     

Effect of bulky substitution on catalytic activity of a manganese salen complex used in biomimetic alkene epoxidation and alkane hydroxylation with sodium periodate

The catalytic activity of Mn(salen)Cl containing tert-pentyl groups at the 3,5-positions of the salen ligand in the epoxidation of alkenes and hydroxylation of alkanes was studied at room temperature, using sodium periodate as an oxygen source. The effects of various axial ligands were investigated in the epoxidation of cyclooctene. Imidazole, as a strong π-donor ligand, was the best axial ligand. The effect of different solvents was studied in the epoxidation of cyclooctene in CH₃CN/H₂O solvent mixture. The epoxidation reactions of cyclooctene by different oxygen donors including NaIO₄, Bu₄NIO₄, KHSO₅, H₂O₂, H₂O₂/urea, NaOCl and tert-BuOOH were also studied and NaIO₄ was selected as oxygen source. The presence of bulky substituents in the 3,5-positions of the salen ligand was found to increase the catalytic activity of this complex.     

12-Tungstophosphoric acid supported on inorganic oxides as heterogeneous and reusable catalysts for the selective preparation of alkoxymethyl ethers and their deprotections under different reaction conditions

A wide variety of primary and secondary alcohols were efficiently converted to their corresponding methoxymethyl (MOM) and ethoxymethyl (EOM) ethers in the presence of catalytic amounts of supported H₃PW₁₂O₄₀ on silica gel and zirconia at room temperature and under microwave irradiation at solvent-free conditions, whereas, phenols and tertiary alcohols remained intact under the same reaction conditions. Deprotection of these ethers to their parent alcohols was also achieved using these heterogeneous catalysts in ethanol, as a green solvent, under reflux conditions and microwave irradiation. Selective deprotection of primary and secondary MOM- and EOM-ethers in the presence of phenolic and tertiary ones, methyl and benzyl ethers, esters and trimethylsilyl ethers was achieved by these reagent systems. The present methodology offers several advantages such as short reaction times, high yields, simple procedure, heterogeneous reaction conditions, selectivity, non-toxicity and reusability of the catalysts.