Zeolite-Hy : A Selective And Efficient Catalyst For The Alcoholyses Of Various Alcohols

An efficient and selective method for the conversion of various alcohols into their corresponding ethers in the presence of zeolite under sorvolytic condition is described. The reaction proceeds efficiently at ambient pressure in high yields.     

Efficient and Ecofriendly Protocol for Tetrahydropyranylation/Depyranylation of Alcohols in the Presence of Tin(II) Chloride Dihydrate

A mild, efficient, and solvent‐free protocol for tetrahydropyranylation of alcohols in the presence of a catalytic amount of SnCl₂ · 2H₂O is reported. Simple filtration of the reaction mixture through a short silica‐gel pad gives the pure products in excellent yields. Depyranylation can also be achieved by adding methanol under similar reaction conditions.     

Solvent-Free Tetrahydropyranylation of Alcohols with Sulfamic Acid as Reusable Catalyst

Abstract

An efficient H₂NSO₃H-catalyzed solvent-free tetrahydropyranylation of various alcohols at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple work-up, and the recyclability of the catalyst were displayed in this article.     

Natural Kaolinitic Clay: A Mild and Efficient Catalyst for the Tetrahydropyranylation and Trimethylsilylation of Alcohols

Natural kaolinitic clay possessing transition metals such as Fe, Ti in its lattice has been found to catalyze efficiently the protection of a variety of alcohols with 2,3-dihydro-4H-pyran (DHP) and hexamethyldisilazane (HMDS) at ambient conditions.     

A Mild and Efficient Tetrahydropyranylation of Alcohols

Triphenylphosphine (TPP)-iodotrimethylsilane (TMSI) was found to be a convenient and highly effective catalyst for the tetrahydropyranylation of aliphatic and aromatic alcohols with dihydropyran in dichloromethane at ambient temperature.     

Dicyanoketene Ethylene Acetal as a Mild and Efficient Catalyst for Tetrahydropyranylation of Alcohols

Alcohols can react with 3,4-dihydro-2H-pyran in the presence of a catalytic amount of dicyanoketene ethylene acetal under neutral conditions to afford the corresponding tetrahydropyranyl ethers in good yields.     

Facile Tetrahydropyranylation of Alcohols and Phenols Using Anhydrous Calcium Chloride under Mild and Neutral Conditions

Summary.  Treatment of 3,4-dihydro-2H-pyran with various alcohols and phenols in the presence of a catalytic amount of anhydrous calcium chloride in dichloromethane furnished tetrahydropyranyl ethers under almost neutral conditions. Corresponding author. E-mail: bandgar_bp@yahoo.com Received January 25, 2002; accepted (revised) March 20, 2002     

SiO2包裹的杂多酸催化剂Cu-H4SiW12O40瞬间催化四氢吡喃化反应

以微乳化法制备的二氧化硅担载的的杂多酸催化剂Cu—H4SiW12O40在室温下能瞬间催化四氢吡喃化反应。且催化剂在至少重复使用四次而未见明显的失活。     

Tetrahydropyranylation of Alcohols and Phenols Using the Synergistic Catalyst System, Copper(II) Chloride-Acetic Acid

Summary. Copper(II) chloride-acetic acid was found to be an efficient synergistic catalytic system for the tetraphydropyranylation of various alcohols and phenols in high yields at room temperature in short reaction times.     

N‐Bromosuccinimide (NBS): A Mild and Efficient Catalyst for Tetrahydropyranylation of Alcohols and Phenols under Solvent‐Free Conditions

Different types of alcohols and phenols are tetrahydropyranylated in the presence of NBS catalyst in good to excellent yields under mild, neutral and solvent‐free conditions.     

Dimethyl Sulfoxide Pivaloyl Chloride: A New Reagent for Oxidation of Alcohols to Carbonyls

An efficient procedure for conversion of alcohols to the corresponding carbonyl compounds, an alternative to the classical Swern oxidation, is described. Pivaloyl chloride is employed as a mild and inexpensive electrophile. A possible reaction mechanism is proposed.     

A Mild and Versatile Method for the Tetrahydropyranylation of Alcohols and Their Detetrahydropyranylation

An efficient and mild method for tetrahydropyranylation of alcohols and their detetrahydropranylation using NH₄Cl is described. This protocol provides a useful alternative tetrahydropyranylation of alcohols and their deprotection at different pH.

     

Search For A New Reagents From The Nitrosoamine Group For Spectrophotometric Determination Of Sulphur Dioxide

Abstract

p-Nitrosodiphenylamine as a representative of nitrosoamine group was tested as a new reagent for the spectrophotometric determination of SO₂. A mixture containing: p-nitrosodiphenylamine, formaldehyde, HCl, di-methylformamide and water was added to the aqueous test solutions of sulphites forming after 5 min, a blue complex with Λ_max=675 nm stable for one hour. The Lambert-Beer law was obeyed in the 0 to 50 /ug SO₂/cm³ range. Molar absorptivity was equal to 2000 and the specific absorption was 0.062. The investigations should lead to search for other reagents from the nitrosoamine group suitable for this purpose.     

Efficient Role of Ionic Liquid (bmim)HSO4 as Novel Catalyst for Monotetrahydropyranylation of Diols and Tetrahydropyranylation of Alcohols

A simple procedure for the monotetrahydropyranylation of diols and alcohols, in excellent to moderate yields, has been reported using a catalytic amount of the acidic ionic liquid, 1‐butyl‐3‐methylimidazolium hydrogensulphate (bmim)HSO₄ under microwave and ultrasonic irradiation. Results have been compared with those obtained by reactions in the absence of these energies, and effectiveness of the recycled ionic liquid has also been studied.     

Magnesium-Tin(II) Chloride Dihydrate: A New System for Chemoselective Reduction of Aldehydes into Alcohols in the Presence of Ketones,Ketalization of Ketones and Dehalogenation of Benzyl Halides

Magnesium-tin (II) chloride dihydrate in THF efficiently reduced aldehydes into their corresponding alcohols chemoselectively in the presence of ketones, formed ketals with ketones and glycol and dehalogenated benzyl halides.     

A Mild and Practical Procedure for Tetrahydropyranylation of Alcohols and Phenols Catalysed by Anhydrous Ferrous Sulfate

Theprotectionofhydroxybyformationoftetrahydropyranyl(THP)ethersisofgreatimportanceinorganicsynhesisparticularlyduringthesynthesisofnaturalproducts.'OwingtotheremarkablestabilityofTHPethersunderavarietyofreactionconditions,suchasneutralandstronglybasicmedia,reactionsinvolvingGrignardreagents,reductionwithhydrides,oxidation,oxidativealkylationandacylation,etc.,tetrahydropyranylationisoneofthemethodsofchoicetoprotectahydroxylgroupsinamultisteporganicsynthesis.'Generallytetrahydropyranylationofa…     

A Mild and Efficient Method for Tetrahydropyranylation/Depyranylation of Alcohols and Phenols Under Neutral Conditions

Alcohols and phenols are tetrahydropyranylated rapidly in high yields in the presence of lithium bromide and dichloromethane at room temperature. Deprotection of these THP ethers can also be effected readily by mere change of the solvent to methanol and refluxing with excess lithium bromide. Due to neutral reaction conditions employed, the method is also compatible with compounds having acid sensitive functional groups.     

Melamine Trisulfonic Acid (MTSA): A New Efficient Catalyst for the Chemoselective Methoxymethylation of Alcohols

Melamine trisulfonic acid, which is easily prepared by the reaction of melamine with neat chlorosulfonic acid, is able to efficiently catalyze the chemoselective methoxymethylation of alcohols with dimethoxymethane (DMM). All reactions were performed under mild and completely heterogeneous reaction conditions in good to high yields.