A novel and highly efficient method for the silylation of alcohols with hexamethyldisilazane (HMDS) catalyzed by recyclable sulfonic acid-functionalized ordered nanoporous silica

Silylation of alcohols with hexamethyldisilazane (HMDS) in dichloromethane provides the corresponding silyl ethers in almost quantitative yields at room temperature using 1-3 mol % of sulfonic acid-functionalized silica. Additionally, the catalyst displays a high activity and thermal stability (up to 240 °C) and it can be easily recovered and reused for at least 20 reaction cycles without loss of reactivity.     

Highly efficient oxidation of alcohols using Oxone as oxidant catalyzed by ruthenium complex under mild reaction conditions

Aromatic and alkyl alcohols were oxidized to the corresponding aldehydes or ketones at room temperature with high conversion and selectivity using Oxone （2KHSOs-KHSO4.K2SO4） as oxidant catalyzed by ruthenium complex Quin-Ru-Quin （where Quin = 8-hydroxyquinoline）. The reaction time is very short and the preparation of complex is simple.     

Mild and efficient method for the cleavage of cyclic and acyclic ethers by iodine under solvent-free conditions

Ethers undergo smooth cleavage with acyl chlorides in the presence of a catalytic amount of elemental iodine under extremely mild conditions to give the corresponding halo esters. This new procedure offers significant advantages such as high conversions, short reaction times and enhanced selectivity together with mild reaction conditions, which makes it an attractive strategy.     

One-pot three-component Mannich reaction catalyzed by iodine under solvent-free conditions

One-pot three-component Mannich reactions of ketones with aromatic aldehydes and aromatic amines are effectively catalyzed by molecular iodine at room temperature under solvent-free conditions to afford the corresponding β-amino carbonyl compounds with moderate to excellent yields. The method has the following advantages: no use of solvent, mild condition, high reaction speed and small quantity of catalyst.     

Highly efficient oxidation of alcohols using Oxone(R) as oxidant catalyzed by ruthenium complex under mild reaction conditions

Aromatic and alkyl alcohols were oxidized to the corresponding aldehydes or ketones at room temperature with high conversion and selectivity using Oxone (2KHSO5·KHSO4·K2SO4) as oxidant catalyzed by ruthenium complex Quin-Ru-Quin (where Quin = 8-hydroxyquinoline). The reaction time is very short and the preparation of complex is simple. 2008 Zi Qiang Lei. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Lithium trifluoromethanesulfonate (LiOTf) as a recyclable catalyst for highly efficient acetylation of alcohols and diacetylation of aldehydes under mild and neutral reaction conditions

A variety of alcohols and aldehydes were reacted with acetic anhydride at room temperature in the presence of a catalytic amount of lithium triflate (LiOTf) to produce the corresponding esters and 1,1-diacetates, respectively, in good to excellent yields under essentially neutral reaction conditions. Sensitive functional groups such as PhCO(2)-, OMe, and OTBDMS ethers survived intact under the described reaction conditions.     

Mild and efficient barbier allylation reaction mediated by magnesium powder under solvent-free conditions

A novel and highly efficient synthesis of homoallylic alcohols is achieved by the allylation of carbonyl compounds using magnesium powder as mediator under solvent-free conditions. A series of aldehydes and ketones are converted to the corresponding homoallylic alcohols, the yields of the reaction is considerably high (85-98%). The procedure is environment benign, operationally simple and easy to scale up at room temperature.     

Mild and efficient silylation of alcohols and phenols with HMDS using Bi(OTf)3 under solvent-free condition

A very efficient and mild silylation of alcohols and phenols with hexamethyldisilazane (HMDS) at rt is developed using Bi(OTf)₃ as the catalyst. Primary, secondary and tertiary alcohols as well as phenols are excellently converted into corresponding TMS ethers in a very short reaction time. This procedure can also be applied to large scale silylation for industrial application.     

An eco-benign and highly efficient procedure for N-acylation catalyzed by heteropolyanion-based ionic liquids using carboxylic acid under solvent-free conditions

An eco-benign and highly efficient route for N-acylation of amines has been developed by treating amines with corresponding carboxylic acids in the presence of 2 mol % of heteropolyanion-based ionic liquids as catalysts under solvent-free conditions. This practical reaction could tolerate a wide range of substrates. Thus, various N-acylation products including N-acyl α-amino acid derivatives were obtained in moderate to excellent yields at 70 °C to 120 °C. Moreover, recycling studies revealed that heteropolyanion-based ionic liquids were easily reusable for this N-acylation. This method provides a green and much improved protocol over the existing methods.     

Mild and efficient tetrahydropyranylation of alcohols and dehydropyranylation of THP ethers catalyzed by ferric perchlorate

A simple, mild and efficient method for tetrahydropyranylation and dehydropyranylation of alcohols in the presence of ferric perchlorate are described.     

Highly efficient three-component Strecker-type reaction catalyzed by MgI2 etherate under solvent-free conditions

A concise, straightforward and efficient method has been developed for the synthesis of α-aminonitriles by an one-pot three-component condensation of aldehydes or ketones, amines and trimethylsilyl cyanide catalyzed by MgI₂ etherate under solvent-free conditions. This protocol has some advantages such as mild reaction condition, simple work-up, short reaction time and high product yields.     

Direct chlorination of alcohols with chlorodimethylsilane catalyzed by a gallium trichloride/tartrate system under neutral conditions

The reaction of secondary alcohols 1 with chlorodimethylsilane (HSiMe(2)Cl) proceeded in the presence of a catalytic amount of GaCl(3)/diethyl tartrate to give the corresponding organic chlorides 3. In the catalytic cycle, the reaction of diethyl tartrate 4a with HSiMe(2)Cl 2 gives the chlorosilyl ether 5 with generation of H(2). Alcohol-exchange between the formed chlorosilyl ether 5 and the substrate alcohol 1 affords alkoxychlorosilane 6, which reacts with catalytic GaCl(3) to give the chlorinated product 3. The moderate Lewis acidity of GaCl(3) facilitates chlorination. Strong Lewis acids did not give product due to excessive affinity for the oxy-functionalities. Although tertiary alcohols were chlorinated by this system even in the absence of diethyl tartrate, certain alcohols that are less likely to give carbocationic species were effectively chlorinated using the GaCl(3)/diethyl tartrate system.     

Iodination of alcohols using triphenylphosphine/iodine under solvent-free conditions using microwave irradiation

A straightforward and effective procedure for the conversion of benzylic, allylic and aliphatic alcohols to the corresponding iodides using Ph₃P/I₂ under solvent-free conditions using microwave irradiation is reported.     

A highly efficient and ecofriendly procedure for tetrahydropyranylation of alcohols and phenols in the presence of in-situ generated I2 under heterogeneous and neutral conditions

Abstract  Molecular iodine generated in situ from Fe(NO₃)₃·9H₂O/NaI acts as a highly efficient catalyst for tetrahydropyranylation of various alcohols and phenols with 3,4-dihydro-2H-pyran in almost quantitative yields. The reaction occurs rapidly in dichloromethane at room temperature, and use of toxic molecular iodine is avoided. Graphical Abstract        

Introducing efficient palladium catalyzed cross coupling reaction of tertiary alcohols and aroyl chlorides for the synthesis of highly substituted esters

Esters are chemical compounds with many practical uses. The common type of esterification is called the Fischer esterification. Another one is by the action of acid chlorides on alcohols but not with tertiary alcohols. The stable carbenium ions formed from tertiary alcohols favor elimination and the byproduct, hydrogen chloride prevents ester formation. In this new report, palladium inserted ArCOPdCl species reacts with tertiary alcohols and cross-coupling under microwave heating, minimizes the formation of probable carbenium ion, and promotes successful production of highly substituted esters in good to high yields.     

A novel method for the highly efficient synthesis of 1,2-benzisoxazoles under neutral conditions using the Ph3P/DDQ system

The use of Ph₃P/DDQ offers a novel, neutral and highly efficient method for the efficient conversion of 2-hydroxyaryl aldoximes and ketoximes to 1,2-benzisoxazoles in excellent yields at room temperature.     

A novel and efficient method for the synthesis of α-aminonitriles by the reaction of aminals with trimethylsilyl cyanide catalyzed by iodine

Iodine, was found to be a practical and novel catalyst for the reaction of aminal and trimethylsilyl cyanide under mild and neutral reaction condition to afford the corresponding α-aminonitriles in high yields and short reaction times. Trimethylsilyl iodide derived in situ from elemental iodine and trimethylsillyl cyanide catalyzed this conversion.     

Lanthanum trichloride: An efficient catalyst for the silylation of hydroxyl groups by activating hexamethyldisilazane (HMDS)

A variety of hydroxy functional groups was protected as their corresponding trimethylsilyl ethers using HMDS in the presence of lanthanum trichloride. The catalyst LaCl₃ activates the HMDS and accelerates the reaction under mild reaction conditions at room temperature to afford the corresponding silylated products in excellent yields.