Silica-bonded S-sulfonic acid as a recyclable catalyst for the silylation of hydroxyl groups with hexamethyldisilazane (HMDS)

2010 ◽  
Vol 88 (2) ◽  
pp. 164-171 ◽  
Author(s):  
Khodabakhsh Niknam ◽  
Dariush Saberi ◽  
Hajar Molaee ◽  
Mohammad Ali Zolfigol
Keyword(s):  
Sulfonic Acid ◽  
Room Temperature ◽  
Reaction Times ◽  
Chlorosulfonic Acid ◽  
Hydroxyl Groups ◽  
Secondary Alcohols ◽  
Mild Conditions ◽  
Trimethylsilyl Ethers ◽  
Phenolic Hydroxyl Groups ◽  
Good Range

Silica-bonded S-sulfonic acid (SBSSA) was prepared by the reaction of 3-mercaptopropylsilica (MPS) and chlorosulfonic acid in tert-butylmethyl ether, and used as a catalyst for the silylation of hydroxyl groups. A good range of primary, secondary alcohols and phenolic hydroxyl groups were effectively converted into their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of SBSSA under mild conditions at room temperature with short reaction times and in good-to-excellent yields. An excellent chemoselective silylation of hydroxyl groups in the presence of other functional groups was also observed. The heterogeneous catalyst was recycled for 30 runs upon the reaction of benzyl alcohol with HMDS without lossing its catalytic activity.

Methylation of Phenolic Hydroxyl Group and Demethylation of Anisoles

2009 ◽  
Vol 2009 (4) ◽  
pp. 229-230 ◽  
Author(s):  
Nobuhiro Sato ◽  
Hiroyuki Endo
Keyword(s):  
Microwave Heating ◽  
Room Temperature ◽  
Reverse Reaction ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups ◽  
Phenyl Ethers ◽  
Methyl Phenyl

A mild methylation of phenolic hydroxyl groups with iodomethane was enabled in the presence of sodium bis(trimethylsilyl)amide at room temperature. The reverse reaction, namely demethylation of methyl phenyl ethers, was easily achieved by microwave heating with neat iodotrimethylsilane.

H3PW12O40 — A selective, environmentally benign, and reusable catalyst for the preparation of methoxymethyl and ethoxymethyl ethers and their deprotections under mild conditions

2008 ◽  
Vol 86 (8) ◽  
pp. 831-840 ◽  
Author(s):  
Iraj Mohammadpoor-Baltork ◽  
Majid Moghadam ◽  
Shahram Tangestaninejad ◽  
Valiollah Mirkhani ◽  
Arsalan Mirjafari
Keyword(s):  
Reaction Times ◽  
Environmentally Benign ◽  
Reusable Catalyst ◽  
Secondary Alcohols ◽  
Selective Protection ◽  
Trimethylsilyl Ethers ◽  
Solvent Free Conditions ◽  
Benzyl Ethers ◽  
High Yields ◽  
Work Up

Different types of primary and secondary alcohols were efficiently transformed to their corresponding methoxymethyl (MOM) and ethoxymethyl (EOM) ethers in the presence of catalytic amounts of H3PW12O40 at room temperature under solvent-free conditions. Selective protection of primary and secondary alcohols in the presence of phenols and tertiary alcohols was achieved by this method. Deprotection of these ethers to their parent alcohols was also performed using this catalyst in ethanol under reflux conditions. We have also found that primary and secondary MOM- and EOM-ethers are selectively deprotected in the presence of phenolic and tertiary ones, methyl and benzyl ethers, esters, and trimethylsilyl ethers by this catalyst. The notable advantages of this protocol are high yields, short reaction times, easy work-up, non-toxicity, easy availability and handling, eco-friendly, and reusability of the catalyst.Key words: methoxymethylation, ethoxymethylation, protection, deprotection, heteropoly acid.

The Dielectric Properties of Symmetrical Long-Chain Secondary Alcohols in the Solid State

1951 ◽  
Vol 4 (2) ◽  
pp. 213 ◽  
Author(s):  
RL Meakins ◽  
RA Sack
Keyword(s):  
Hydrogen Bonding ◽  
Solid State ◽  
Dielectric Loss ◽  
Low Temperatures ◽  
Room Temperature ◽  
Molecular Chain ◽  
Hydroxyl Groups ◽  
Crystal Formation ◽  
Secondary Alcohols ◽  
Long Chain

Symmetrical long-chain secondary alcohols in the solid state show very high dielectric loss at audio and radio frequencies. This can be explained by the presence of chains of hydroxyl groups linked by hydrogen bonding and capable of reversing their direction. Further evidence of hydrogen bonding is provided by a study of the melting points of the secondary alcohols and related compounds. The amount of dielectric loss depends markedly on the manner of formation of the solid, being smallest for samples formed by recrystallization from solvents at low temperatures and largest for specimens obtained by slow cooling from the melt. The alcohols of molecular chain-lengths of 13, 15,17, and 19 carbon atoms show a considerable decrease of absorption on storing at room temperature. For alcohols of between 23 and 43 carbon atoms the loss is rather smaller with a peak at higher frequencies, but remains more constant in time. These results are interpreted in terms of competing influences of van der Waals forces and hydrogen bonds during crystal formation ; the former, which lead to a structure unsuitable for the formation of hydrogen-bond chains, are predominant at low temperatures, but become more rapidly neutralized by thermal motion, especially for the shorter molecules. The high temperature modification of the lower homologues is unstable at room temperature, and a molecular diffusion process causes the bond chains to break. Dilute systems of secondary alcohols with hydrocarbons or paraffin wax of similar molecular chain-length show very small dielectric loss suggesting a solid solution in which bond chains cannot be formed ; if the paraffin molecules are appreciably longer, the absorption is large and decreases on storing, presumably owing to the presence of a pure alcohol phase. I.

scholarly journals REGIOSELECTIVE AND FACILE OXIDATIVE THIOCYANATION OF ANILINES AND INDOLES WITH TRANS-3,5‐DIHYDROPEROXY‐3,5‐DIMETHYL‐1,2‐DIOXOLANE

2014 ◽  
Vol 10 (8) ◽  
pp. 3088-3096 ◽  
Author(s):  
Davood Azarifar ◽  
Maryam Golbaghi ◽  
Mahtab Pirveisian ◽  
Zohreh Najminejad
Keyword(s):  
Room Temperature ◽  
Reaction Times ◽  
Sodium Thiocyanate ◽  
Oxidative Potential ◽  
Mild Conditions ◽  
In Situ Generation

Oxidative potential of trans‐3,5‐dihydroperoxy‐3,5‐dimethyl‐1,2‐dioxolane (DHPODMDO) has been explored in the facile thiocyanation of anilines and indoles through the efficient and in situ generation of SCN+ ion from sodium thiocyanate. The reactions proceed with regioselectivity under mild conditions at room temperature to afford the respective thiocyanate derivatives in excellent yields and low reaction times.

scholarly journals Routes involving no free C2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C2.

2021 ◽  
Author(s):  
Henry Rzepa
Keyword(s):  
Chemical Synthesis ◽  
Gas Phase ◽  
Room Temperature ◽  
Mechanistic Model ◽  
Reaction Times ◽  
Carbon Chain ◽  
Isotopic Substitution ◽  
Ambient Temperatures ◽  
Mild Conditions ◽  
Displacement Reactions

<p>Recent lively debates about the nature of the quadruple bonding in the diatomic species C<sub>2</sub> have been heightened by recent suggestions of molecules in which carbon may be similarly bonded to other elements. The desirability of having methods for generating such species at ambient temperatures and in solution in order to study their properties may have been realized by a recent report of the first chemical synthesis of free C<sub>2</sub> itself under mild conditions. The method involved unimolecular fragmentation of an alkynyl zwitterion<b> 2</b> as generated from the precursor <b>1</b>, resulting in production and then trapping of free C<sub>2</sub> at ambient temperatures rather than the high temperature gas phase methods normally employed for C<sub>2</sub> generation. Here, alternative mechanisms are proposed for this reaction based on DFT calculations involving bimolecular 1,1- or 1,2-iodobenzene displacement reactions from <b>2</b> directly by galvinoxyl radical, or hydride transfer from 9,10-dihydroanthracene to <b>2</b>. These mechanisms result in the same trapped products as observed experimentally, but unlike that involving unimolecular generation of free C<sub>2</sub>, exhibit calculated free energy barriers commensurate with the reaction times observed at room temperatures. The relative energies of the transition states for 1,1 <i>vs</i> 1,2 substitution provide a rationalisation for the observed isotopic substitution patterns. The same mechanism also provides an energetically facile path to polymeric synthesis of carbon rich species by extending the carbon chain attached to the iodonium group, eventually resulting in formation of amorphous carbon and discrete molecules such as C<sub>60</sub>.</p><div><div><p><br></p></div></div>

scholarly journals Highly Efficient and Facile Method for Synthesis of 2-Substituted Benzimidazoles via Reductive Cyclization of O-Nitroaniline and Aryl Aldehydes

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Hossein Naeimi ◽  
Nasrin Alishahi
Keyword(s):  
Room Temperature ◽  
Reaction Times ◽  
Starting Material ◽  
Reductive Cyclization ◽  
Aryl Aldehydes ◽  
Mild Conditions ◽  
Highly Efficient ◽  
Convenient Synthesis

A versatile and convenient synthesis of 2-substituted benzimidazoles, using o-nitroaniline as starting material with several aryl aldehydes, has been accomplished by using a small amount of a reluctant agent. The reaction was carried out under very mild conditions at room temperature. The yields obtained are very good in reasonably short reaction times.

Protection of hydroxy groups as trimethylsilyl ethers using 1,1,1,3,3,3-hexamethyldisilazane (HMDS) catalyzed by poly(4-vinylpyridinium tribromide)

2010 ◽  
Vol 75 (5) ◽  
pp. 607-615 ◽  
Author(s):  
Arash Ghorbani-Choghamarani ◽  
Mohammad Ali Zolfigol ◽  
Maryam Hajjami ◽  
Khorshid Darvishi ◽  
Laleh Gholamnia
Keyword(s):  
Room Temperature ◽  
Efficient Procedure ◽  
Mild Conditions ◽  
Trimethylsilyl Ethers ◽  
Hydroxy Groups

A very efficient procedure for the protection of alcohols and phenols is presented. The mixture of 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and catalytic amounts of poly(4-vinylpyridinium tribromide) was found to be effective for the trimethylsilylation of alcohols and phenols. Protection reaction is very simple and performs heterogeneously in acetonitrile at room temperature under mild conditions.

scholarly journals SbCl3-Catalyzed conversion of ketones and aldehydes into gem-dihydroperoxides (DHPs) with 30% H2O2

2015 ◽  
Vol 11 (5) ◽  
pp. 3547-3553 ◽  
Author(s):  
Davood Azarifar ◽  
Boshra Mahmoudi ◽  
Kaveh Khosravi
Keyword(s):  
Present Method ◽  
Room Temperature ◽  
Reaction Times ◽  
Experimental Procedure ◽  
Mild Conditions ◽  
Efficient Conversion ◽  
High Yields ◽  
Catalyzed Oxidation

A simple and efficient conversion of ketones and aldehydes into corresponding gem-dihydroperoxides (DHPs) has been developed by SbCl3-catalyzed oxidation with 30% H2O2 at room temperature. The reactions proceeded smoothly under mild conditions at room temperature. Simple experimental procedure, use of inexpensive and non-toxic catalyst, high yields and low reaction times are the main merits of the present method.

scholarly journals Melamine Trisulfonic Acid as a Highly Efficient and Reusable Catalyst for the Synthesis of β-Acetamido Ketones

2012 ◽  
Vol 9 (4) ◽  
pp. 2322-2331 ◽  
Author(s):  
Abdolkarim Zare
Keyword(s):  
Sulfonic Acid ◽  
Room Temperature ◽  
Acetyl Chloride ◽  
Reaction Times ◽  
Aromatic Aldehydes ◽  
Reusable Catalyst ◽  
One Pot ◽  
Highly Efficient ◽  
The One ◽  
Melamine Trisulfonic Acid

A highly efficient protocol for the one-pot multi-component condensation of acetophenones with aromatic aldehydes, acetonitrile and acetyl chloride in the presence of melamine trisulfonic acid (MTSA) as a highly efficient and recyclable sulfonic acid-containing catalyst at room temperature is described. In this method, β-acetamido ketone derivatives are obtained in high to excellent yields and in relatively short reaction times.

Efficient green synthesis of monomethine cyanines via grinding under solvent-free conditions

2016 ◽  
Vol 5 (3) ◽  
Author(s):  
Fayez M. Eissa ◽  
Reda S. Abdel Hameed
Keyword(s):  
Room Temperature ◽  
Reaction Times ◽  
Solvent Free ◽  
Synthetic Method ◽  
Mild Conditions ◽  
Green Approach ◽  
Solvent Free Conditions ◽  
Reported Data ◽  
Layer Chromatography ◽  
Inexpensive Procedure

AbstractA solvent-free, efficient, and green approach for the synthesis of monomethine cyanine dyes was carried out via grinding at room temperature in the presence of a minimum amount of catalyst. This green methodology aims to overcome the limitations and drawbacks of previously reported methods such as heating at high temperatures, use of large amounts of catalysts, use of solvents, modest yields, and long reaction times. Moreover, the advantages of the process include mild conditions with excellent conversion, and inexpensive procedure. The new synthetic method was demonstrated for eight reported dyes, as representatives, and showed high applicability for their analogues in the same way. The green context of the new methodology was noticeable, compared with the non-green components of the conventional one. The structure and purity of the resulting compounds were compared with the previously reported data and confirmed using thin layer chromatography, absorption spectra, elemental analysis, mass spectrometry,

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