Convenient and Efficient Method for the Iodination of Benzylic and Aliphatic Alcohols by Using Al(HSO4)3/KI in Nonaqueous Solution

A simple and efficient method for the iodination of benzylic and aliphatic alcohols by using Al(HSO₄)₃/KI in n‐hexane as solvent is reported. Mild reaction conditions and good to excellent yields of the products are the noteworthy advantages of the method.     

KAl(SO4)2 · 12H2O (alum) a reusable catalyst for the synthesis of some 4-substituted coumarins via Pechmann reaction under solvent-free conditions

A simple, efficient, and practical procedure for the Pechmann condensation using KAl(SO₄)₂ · 12H₂O (alum) as a non-toxic, reusable, inexpensive, and easily available catalyst is described under solvent-free condition at 65°C. These improved reaction conditions allow the preparation of a wide variety of some new substituted coumarins in high yields (86–96%) and purity under mild reaction conditions. Compared to the classical Pechmann condensation, this new method consistently has the advantage of high yields. Correspondence: Ali A. Mohammadi, Department of Chemistry, Shahid Beheshti University, P.O. Box 19839-4716, Tehran, Iran.     

A Mild,Simple, Efficient,and Selective Protection of Hydroxyl Groups Using Silica-Supported Sodium Hydrogen Sulfate as a Heterogeneous Catalyst

A mild, simple, novel, and highly efficient method for the rapid protection of various primary, secondary, tertiary aliphatic alcohols, aromatic alcohols, and oximes using hexamethyldisilazane (HMDS) in the presence of silica-supported sodium hydrogen sulfate (NaHSO ₄ -SiO ₂ ), as an active, inexpensive, nontoxic, heterogeneous, and readily available catalyst under ambient conditions is described. Timethylsilyl ethers were prepared in high to excellent yields, with short reaction times under mild and almost neutral reaction conditions at room temperature.     

Chemoselective Deprotection of Thioacetals/Thioketals Using HIO3 in the Presence of Wet SiO2 Under Mild Solvent-Free Conditions

Abstract

HIO ₃ in the presence of wet SiO ₂ is highly efficient and a mild reagent for selective deprotection of a variety of thioacetals/thioketals to the corresponding parent carbonyl compounds at room temperature and under solvent-free conditions.     

H6P2W18O62·14H2O as an efficient catalyst for the green synthesis of α-aminophosphonates from α-amino acids

Abstract

A simple, efficient and eco-friendly protocol has been described for the synthesis of α-aminophosphonates via Kabachnik-Fields reaction, catalyzed by H₆P₂W₁₈O₆₂·14H₂O as a reusable catalyst. The reaction was realized by condensation of amino acids, various aromatic aldehydes and triethylphosphite under solvent-free conditions, the corresponding α-aminophosphonates were formed in good yields. All the new products were characterized by IR, ¹H, ¹³C and ³¹P-NMR analyses. This method offers advantages such as simplicity workup with the green aspects, good yields and short reaction times.     

Oxidation of Sulfides with Hydrogen Peroxide Catalyzed by Vitamin B2 Derivatives

5-Ethyl-3-methyl-2′,4′:3′,5′-di-O-methylenedioxyriboflavinium perchlorate (1, DMRFlEt⁺ClO₄ ^–), derived readily from commercially available vitamin B₂ (riboflavin), exhibits high catalytic activity for the oxidation of organic sulfides with hydrogen peroxide. The reaction provides an efficient and selective method for the oxidative transformation of organic sulfides to the corresponding sulfoxides under mild conditions.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Silica-gel-supported Ce(SO4)2·4H2O-mediated cyclization of 2′-amino and 2′-hydroxychalcones under solvent-free conditions

A simple, efficient, and environmentally friendly approach for the synthesis of flavones, aza-flavones, and aza-flavanones from corresponding 2′-hydroxy or 2′-aminochalcones has been developed. The reactions are successfully conducted in presence of silica-gel-supported Ce(SO₄)₂·4H₂O under solvent-free conditions.     

Encapsulation of Pd(II) by N4 and N2O2 macrocyclic ligands: their use in catalysis and biology

New macrocyclic Schiff base Pd(II) compounds were synthesized by treating N₄ and N₂O₂ macrocycles with palladium chloride in a 1 : 1 ratio. The resulting macrocyclic compounds were characterized by elemental, IR, ¹H-NMR, ¹³C-NMR, mass, molar conductance, magnetic susceptibility, electronic spectra, and thermal analysis. These compounds were used as catalysts in the development of an efficient catalytic method for reduction of organic substrates having nitro, olefinic, acetylenic, and aldehyde groups under mild reaction conditions. The biological activities of all the macrocycles and macrocyclic Pd(II) compounds have been tested against gram positive (Bacillus subtilis and Staphylococcus aureus) and gram negative (Escherichia coli and Klebsiella pneumonia) bacteria and found to be more active than commercially available antibacterial drugs like Streptomycin and Ampicillin.     

Mild and Efficient Deoxygenation of Sulfoxides to Sulfides Using HfCl4/KBH4 System

HfCl₄/KBH₄ was found to be a facile, efficient, convenient, and chemoselective system for the deoxygenation of dialkyl, diaryl, and aryl alkyl sulfoxides, especially for the reduction of dibenzyl sulfoxide to the corresponding sulfides under mild conditions. In addition, the HfCl₄/KBH₄ system could be used in reduction of some other sulfur-bearing substrates to the corresponding sulfides, such as 2,2′-dibenzothiazolyl disulfide, but this reducing system could not reduce sulfolane, diphenyl sulfone, p-toluenesulfonic acid, and p-toluenesulfonyl chloride to their corresponding thiophenols.     

Stannous Chloride–Promoted Synthesis of S-Allyl-N-aryl Dithiocarbamates under Solvent-Free Conditions

Abstract

A highly efficient method of synthesis of S-allyl-N-aryl dithiocarbamates using SnCl₂ as a catalyst under solvent-free conditions is described. The mild reaction conditions, high yields, and shorter reaction period illustrate the good synthetic utility of this method.     

Solvent-free sonochemical kabachnic-fields reaction to synthesize some new α-aminophosphonates catalyzed by nano-BF3•SiO2

To obtain a rapid, efficient synthesis of some new α-aminophosphonates, ultrasonic irradiation has been applied to the reaction mixtures containing amine, aromatic or heteroaromatic aldehydes and triethyl phosphite. The Kabachnik-Fields reaction was performed by using nano-BF₃?SiO₂ as a recyclable catalyst under solvent free conditions. Key advantages of this procedure consist in the eco-friendly and highly efficient reaction conditions, high yields, an easy work-up procedure, short reaction times and solvent free conditions. All title compounds were characterized by spectral and elemental analysis. They were further screened for their in vitro antioxidant activity by the DPPH, O^2? and NO methods. The majority of the title compounds showed good antioxidant activity when compared with the standard antioxidants.     

Regioselective Ring Opening of Styrene Oxide Catalyzed by MoO2(acac)2

The ring-opening reaction of styrene oxide with various nitrogen, oxygen, and carbon nucleophiles catalyzed by MoO₂(acac)₂ was described. The corresponding ring-opening compounds with nearly 100% regioselectivities were obtained under mild conditions in moderate to good yields. MoO₂(acac)₂ is a highly efficient catalyst for the ring opening of styrene oxide. The reaction serves as a simple and efficient method for the synthesis of 1,2-bifunctional compounds.     

H6P2W18O62·18H2O–Catalyzed,Three-Component,One-Pot Synthesis of Indeno[1,2-b]quinoline-7-one Derivatives

In this work, a rapid and efficient one-pot method for the synthesis of indeno[1,2-b]quinoline-7-one derivatives by condensation of 1-naphthylamine, 1,3-indanedione, and different aldehydes in the presence of H₆P₂W₁₈O₆₂·18H₂O as a green and reusable catalyst in refluxing acetic acid is described.     

A Convenient Method for the Aerobic Oxidation of Thiols to Disulfides

Thiols are oxidized to the corresponding disulfides using K⁺/CH ₃ CN system under ambient conditions in the presence of air. This system provides a convenient, rapid, and efficient aerobic oxidative for the syntheses of symmetrical disulfides.     

H2SO4-SiO2: Highly Efficient and Reusable Catalyst for per-O-Acetylation of Carbohydrates Under Solvent-Free Conditions

Sulfuric acid immobilized on silica gel (H₂SO₄-SiO₂) was used as an efficient promoter for per-O-acetylation of carbohydrates with acetic anhydride under solvent-free conditions. The substrates include not only monosaccharides and disaccharides, but also glycosides. The catalyst is recyclable and stable at room temperature, and the reaction protocol is simple, is cost-effective, and gives good isolated yield with high purity. The large-scale reactions also proceeded conveniently and in high yields.     

An Efficient Procedure for the Synthesis of Benzoxazole and Benzothiazole Derivatives Using a H2O2/SiO2-FeCl3 System

A series of benzoxazole and benzothiazoles was readily prepared from the reaction of ortho-aminophenol/ortho-aminothiophenol and aldehydes using solid silica supported ferric chloride (SiO₂-FeCl₃) as catalyst followed by oxidation with H₂O₂ under ambient conditions. Some of advantages of this method are a simple and convenient procedure, easy purification, and shorter reaction times.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

First sonochemical,simple and solvent-free synthesis of chiral tert-butanesulfinimines using silica supported p-toluenesulfonic acid

A solvent-free, versatile procedure has been developed for the effective synthesis of tert-butanesulfinylimines of a variety of aldehydes using chiral tert-butanesulfinamides under green, sonochemical conditions. This method utilizes silica supported p-toluenesulfonic acid (pTSA·SiO₂) as an efficient, safer and inexpensive catalyst under aerobic conditions. The practicable simplicity, easy preparation of the catalyst from readily available substances, high substrate scope, excellent yields of products in short reaction times and environmentally benign (solvent-free sonochemical) conditions are the exceptional assets of this finding.     

g-C_3N_4/CaTi_2O_5复合材料制备及其光催化性能

利用类石墨氮化碳(g-C_3N_4)和亚稳相钙钛氧化物(CaTi_2O_5)固相法制备C_3N_4/CaTi_2O_5复合材料。利用X射线衍射(XRD)、金相显微镜、扫描电子显微镜(SEM)及附带能谱分析仪(EDS)和N2吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计(UV-Vis)测试了样品的光吸收性能,研究C_3N_4与CaTi_2O_5物质的量之比(nC_3N_4/nCaTi_2O_5)对C_3N_4/CaTi_2O_5复合样品的物相结构和微观形貌的影响,同时考察C_3N_4/CaTi_2O_5复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明:相比纯C_3N_4和CaTi_2O_5样品,C_3N_4/CaTi_2O_5复合样品在可见光下具有较高的光催化性能,随着nC_3N_4/nCaTi_2O_5增加,样品的光催化降解率随之增加而后降低,当nC_3N_4/nCaTi_2O_5=1∶1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

Efficient Protocol for Stereoselective Epoxidation of Cinnamic Esters Using TsNBr2

An efficient method has been developed for the synthesis of epoxide from cinnamic esters without any catalyst. The reaction was performed in CH₃CN–water (4:1) using N,N-dibromo-p-toluenesulfonamide (TsNBr₂) in alkaline conditions. This procedure can be utilized for stereoselective synthesis of epoxides from cinnamic esters in excellent yield in a shorter reaction time with exclusive formation of the trans-isomer. The method was further extended successfully for styrenes.     

Rapid SnCl<Subscript>2</Subscript> catalyzed phenylselenoetherification of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-hex-4-en-1-ols

A fast and efficient method for intramolecular heterocyclization of (Z)- and (E)-hex-4-en-1-ols was developed. The method does not cause side reactions of the substrates and provides the cyclic phenylselenoethers in high yields after only few minutes. A catalytic amount of SnCl₂ increased the yield, but in the presence of an equimolar amount of SnCl₂, formation of corresponding cyclic ethers were almost quantitative and reaction occurred instantaneously under extremely mild experimental conditions. Correspondence: Zorica M. Bugarčić, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, P.O.Box 60, YU-34000 Kragujevac, Serbia.