Hydrogen transfer type oxidation of alcohols by rhodium and ruthenium catalyst under microwave irradiation

Secondary alcohols were converted into the corresponding ketones by methyl acrylate and rhodium catalyst efficiently under microwave irradiation. Treatment of primary alcohols with the same condition resulted in the recovery of the starting materials. Primary alcohols were converted into aldehydes by hydrogen transfer reaction using methyl vinyl ketone and ruthenium catalyst under microwave irradiation.     

DABCO,A REAGENT FOR DEPROTECTION OF BENZYLIC TRIMETHYLSILYL ETHERS UNDER MICROWAVE IRRADIATION IN A SOLVENTLESS SYSTEM

Deprotection of trimethylsilyl ethers of benzylic alcohols to the corresponding alcohols using 1,4-diazobicyclo[2,2,2]octane (DABCO) under microwave irradiation under solvent-free conditions is reported.     

Simple Protocol for Synthesis and Cleavage of Tetrahydropyranyl Ethers Using FeSO4 as an Inexpensive Catalyst

Protection and deprotection of alcohols and phenols as tetrahydropyranyl ethers (THP ethers) using an hydrous FeSO₄ under microwave irradiation without solvent is carried out.     

Chromium Trioxide on H-Y Zeolite: Rapid Oxidation of Alcohols to Carbonyl Compounds in Solventless System Using Microwaves

In an environmentally benign solventless system, alcohols are rapidly oxidized to carbonyl compounds using HY-zeolite supported chromium trioxide as an oxidant under microwave irradiation.     

Chromium Trioxide Supported onto Wet Silica Gel: Rapid Oxidation of Alcohols to Carbonyl Compounds Under Microwave Irradiation in Solventless System

In an environmentally benign system, alcohols are rapidly oxidized to carbonyl compounds using CrO 3 supported onto wet silica gel as an oxidant under microwave irradiation.     

Oxidation of benzylic and some aliphatic alcohols 1,2-ethylenebis(triphenylphosphonium)chlorochromate (EBTPPCC): As a new,an efficient and mild oxidant

1,2-Ethylenebis(triphenylphosphonium)chlorochromate was quantitatively prepared and used for the oxidation of various benzylic and some aliphatic alcohols to their corresponding carbonyl compounds in water or acetonitrile and under microwave irradiation. This new oxidizing agent has advantages over similar oxidants in terms of the amount of used oxidant, short reaction time, simple work-up, and high yields. Furthermore, the oxidation of alcohols occurred under microwave irradiation many times and it produced the corresponding carbonyl compounds with high yields and short reaction times, when compared with the conventional method. Finally, the oxidation of different alcohols were accomplished in water under reflux condition with good yields as green chemistry.     

A Facile One Stage Synthesis of Oxazolines Under Microwave Irradiation

A rapid, high yielding procedure for the synthesis of 2-substituted oxazolines has been achieved under microwave irradiation from alkyl and aryl nitriles and β-amino alcohols using a mild Lewis acid catalyst.     

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.     

Microwave-Accelerated Organic Reactions

The use of microwave technology in accelerating organic reactions has received intense attention leading to immense growth recently. Accordingly, we have been interested in improving the efficacy of organic processes by microwave irradiation. Here we report our results on the microwave assisted 1,3-dipolar cycloaddition reaction of nitrile oxides with allylic alcohols, the cleavage reaction of 1,3-diketones under alkaline conditions, and the formation of carbamates from isocyanates with alcohols. The reactions carried out under microwave irradiation, in general, required considerably less reaction time and afforded the desired products in higher yields than those under classical conditions. In all the cases we have studied, the procedures are simplified, the purity of the products are higher, and the cost of reaction is greatly reduced employing microwave.     

Microwave-assisted oxidation of alcohols using Magtrieve™

Primary and secondary alcohols can be selectively oxidized under microwave irradiation into the corresponding aldehydes and ketones within 5-30 min using commercially available and magnetically retrievable Magtrieve™.     

Silylation of Hydroxy Groups with HMDS Under Microwave Irradiation and Solvent-Free Conditions

Phenols and alcohols are silylated with hexamethyldisilazane (HMDS) under microwave irradiation in solvent-free condition in good to excellent yields.     

Facile Preparation of Benzylic Iodides Under Solvent‐Free Conditions Using Microwave Irradiation

Abstract

Benzylic alcohols are rapidly converted to the corresponding benzylic iodides using combination of p‐toluenesulfonic acid (PTSA) and potassium iodide under solvent‐free microwave irradiation conditions.     

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.     

Efficient oxidation of benzylic alcohols with [hydroxy(tosyloxy)iodo]benzene under microwave irradiation

An efficient method for the oxidation of benzylic alcohols with [hydroxy(tosyloxy)iodo]benzene under solvent-free microwave irradiation conditions is described.     

Deoxyfluorination of alcohols using N,N-diethyl-α,α-difluoro-(m-methylbenzyl)amine

Deoxyfluorination of alcohols was carried out using N,N-diethyl-α,α-difluoro-(m-methylbenzyl)amine (DFMBA). Primary alcohols were effectively converted to fluorides under microwave irradiation or conventional heating. Deoxyfluorination of an anomeric hydroxy group in sugars by DFMBA proceeded at below room temperature and glycosyl fluorides could be obtained in good yields. The deoxyfluorination reaction chemoselectively proceeded and various protecting groups on the sugar can survive under the reaction conditions.     

Chemoselective Protection of Hydroxyl Groups and Deprotection of Silyl Ethers

 Trimethylsilylation of alcohols and phenols is carried out using hexamethyldisilazane and LiClO₄ under microwave irradiation and neutral conditions. The deprotection of silyl ethers is carried out similarly using natural kaolinitic clay and a few drops of water.     

Manganese(II) salts as efficient catalysts for chemo selective transesterification of β-keto esters under non-conventional conditions

Transesterification of β-ketoesters with various alcohols has been studied under conventional and non-conventional conditions using desktop chemicals such as Mn(II) salts as catalysts. These methods offered transesterification of β-ketoesters in good yields with dramatic rate accelerations and reduced reaction times. The developed protocols under nonconventional methods such as sonication and microwave irradiation are highly promising compared with the existing procedures.     

Microwave-assisted asymmetric ring opening of meso-epoxides with aromatic amines catalyzed by a Ti-S-(−)-BINOL complex

Catalytic asymmetric ring opening of cyclohexene oxide and meso-stilbene oxide with anilines was catalyzed by a Ti-(S)-(−)-BINOL complex to afford β-amino alcohols in high yield (up to 95%) and good enantioselectivities (ee up to 55%) under microwave irradiation. The reaction using a microwave was found to be 10 times faster than traditional oil-bath heating with retention of enantioselectivity.     

Facile N-Alkylation of Anilines with Alcohols Over Raney Nickle Under Microwave Irradiation

The anilines could be easily and selectively N-alkylated with alcohols in the presence of a small amount of Raney nickel and with a greatly shortened period under microwave irradiation. A purely non-thermal effect of microwave was observed in the reaction.     

Chemoselective Protection of Hydroxyl Groups and Deprotection of Silyl Ethers

Summary.  Trimethylsilylation of alcohols and phenols is carried out using hexamethyldisilazane and LiClO₄ under microwave irradiation and neutral conditions. The deprotection of silyl ethers is carried out similarly using natural kaolinitic clay and a few drops of water. Received March 1, 2001. Accepted (revised) April 17, 2001