Molybdenum Catalyzed Protective Tetrahydropyranylation of Alcohols and Phenols

Molybdenyl(VI) acetylacetonate is an effective catalyst for the protective tetrahydropyranylation of alcohols and phenols.     

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…     

GaI_3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

Introduction Tetrahydropyranylation is an efficient method for the protection of hydroxyl group in organic synthesis due to the stability of the tetrahydropyranyl acetals because they are stable under a variety of reaction conditions such as alkaline media, Grignard reagents, lithium al-kyls, metal hydrides, oxidative reagents, alkylating and acylating reagents.1 Tetrahydropyranyl acetals are gen-erated by a nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP). A variet…     

Solvent-Free NaHSO4-SiO2-Catalyzed Efficient Tetrahydropyranylation of Alcohols and Phenols

A simple and efficient tetrahydropyranylation of alcohols and phenols has been developed using NaHSO₄-SiO₂ (0.5 mol%) as a catalyst under solvent-free conditions to yield corresponding tetrahydropyranyl ethers in excellent yields.     

Tetrahydropyranylation of Alcohols and Phenols Using Polystyrene Supported Lewis Acids as Catalysts

Polystyrene supported TiCl₄ (Ps‐TiCl₄) and polystyrene supported FeCl₃ (Ps‐FeCl₃) were prepared by coordinating Lewis acids with polystyrene. The catalysts were characterized by TGA, BET, SEM, IR and pyridine‐adsorbed IR. The loading of Ps‐TiCl₄ and Ps‐FeCl₃ were 0.35 and 0.3 mmol·g^?1 respectively. Both catalysts were found to be efficient for the tetrahydropyranylation and detetrahydropyranylation of various alcohols and phenols in different solvents. Two catalysts can be recovered and reused for five times with good activity.     

Sulfamic Acid Catalysed Acetylation of Alcohols and Phenols with Acetic Anhydride

An easy acetylation of alcohols and phenols with acetic anhydride has been carried out in excellent yield under catalysis of sulfamic acid.     

乙酸促进邻甲基苯磺酸铜选择性催化醇和酚的四氢吡喃化反应

室温无溶剂条件下, 乙酸能有效促进邻甲基苯磺酸铜催化一系列醇或酚和3,4-2H-二氢吡喃反应, 生成相应的四氢吡喃醚. 在乙酸存在条件下, 体系的催化性能有显著提高, 邻甲基苯磺酸铜用量仅需0.3 mol%(占醇或酚的摩尔分数)就能使反应在较短时间内完成. 反应结束后, 邻甲基苯磺酸铜经简单相分离可多次重复使用, 催化活性无明显下降. 产物结构经IR, 1H NMR, 元素分析进行表征.     

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     

Sulfonated Charcoal,a Mild and Efficient Reagent for the Tetrahydropyranylation of Alcohols and Phenols

Sulfonated charcoal has been demonstradted to be very effective and mild catalyst for the tetrahydropyranylation of alcohols and phenols.     

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.     

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.     

Tetrahydropyranylation of Alcohols Under Solvent-Free Conditions

A green, efficient, and large-scale method for tetrahydropyranylation of alcohols in the presence of a catalytic amount of pyridinium chloride at room temperature under solvent-free conditions is reported.     

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.     

A Mild and Efficient Tetrahydropyranylation and Detetrahydropyranylation of Alcohols and Phenols by VCl<Subscript>3</Subscript>

Vanadium chloride is found to be an efficient catalyst for the tetrahydropyranylation and detetrahydropyranylation of various alcohols and phenols, giving good yields at room temperature and short reaction times. __________ Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1634–1636, November, 2005.     

Copper(II)chloride Catalyzed Tetrahydropyranylation of Alcohols

A simple and efficient methodology for the tetrahydropyranylation of alcohols using catalytic amount of copper(II)chloride in dichloromethane is described. The yields obtained are good to excellent.     

Alpo4 and Alpo4-Al2O3 as New Heterogeneous Catalysts for the Solvent-Free Tetrahydropyranylation of Alcohols and Phenols

OH-protection of alcohols and phenols by heating the hydroxylated compound with 3,4-dihydro-2H-pyrane in the presence of an AlPO₄ or AlPO₄-Al₂O₃ heterogeneous acid catalyst is described. Isolated yields, not optimized, were in the range 50–99%.     

Magnesium Bromide Catalysed Acylation of Alcohols

Magnesium bromide is an efficient catalyst for the acetylation and benzoylation of a variety of primary and secondary alcohols with the respective acid anhydrides at ambient temperature. Acetylation of tertiary alcohols requires subambient temperature to suppress competing dehydration. Coordinating solvents retard the acylation process.     

Melamine-Trisulfonic-Acid-Catalyzed Trimethylsilylation of Alcohols and Phenols

Abstract

A highly convenient method for the trimethylsilylation of alcohols and phenols via treatment by hexamethyldisilazane in the presence of melamine trisulfonic acid as a catalyst has been developed. A wide variety of hydroxyl groups were selectively protected under solvent-free conditions.

GRAPHICAL ABSTRACT