Lithium Perchlorate In Diethyl Ether Research Articles

A Simple Three-Component Reaction for the Preparation of Silylated Primary Amines

In the presence of lithium perchlorate in diethyl ether, three-component reaction between aldehydes, hexamethyldisilazane, and silylated nucleophiles proceeded smoothly to afford trimethylsilylated primary amines in good yields. © 1997 Elsevier Science Ltd.

The cause of the rate acceleration by diethyl ether solutions of lithium perchlorate (LPDE) in organic reactions. Application to high pressure synthesis

Abstract Kinetic studies of isoprene cyclodimerization show that the accelerating effect caused by LPDE (solution of lithium perchlorate in diethyl ether) in some organic reactions cannot be ascribed to internal pressure of LPDE. The kinetic effect is essentially due to catalysis through Li+. Additional arguments are provided by comparison of yields obtained in LPDE (0,1 MPa) and in organic solvents (under pressure) for Diels-Alder reactions of various electronic types. Combination of high pressure and LPDE catalysis is revealed as an excellent multiactivation process to achieve difficult syntheses, but only for [4+2] cycloadditions.

Application of Two-dimensional Covariance Analysisto Infrared Spectroscopic Studies of Electrolyte Solutions

Two-dimensional correlation analysis is applied, for the first time, to aid in structural studies of electrolyte solutions. Concentration dependent spectral features due to solute–solvent and solute–solute interactions can be separated from each other and their relative correlated changes established. The application of 2D correlation analysis, using a generalized covariance approach, is demonstrated using FTIR–ATR data for sub-molar concentrations of lithium perchlorate in diethyl ether. Although it has been established that, as the electrolyte salt concentration increases, the concentration of diethyl ether in the trans–trans conformation decreases relative to diethyl ether in the trans–gauche conformation, no evidence of these changes could be seen in the methyl and methylene C–H stretching bands. This region of the mid-IR spectra was previously thought to show no solute–solvent dependent bands. The 2D covariance analysis performed in this study shows clearly that methyl and methylene stretching modes can be associated uniquely with either the trans–trans or the trans–gauche conformer.

Tandem [2+2] cycloaddition-cycloreversion reactions in highly polar media: A convergent one-pot entry to substituted alkenes and dienes

Reaction at room temperature between acyl chlorides and aromatic or α,β-unsaturated aldehydes in the presence of a tertiary base and in 5M lithium perchlorate-diethyl ether (5M LPDE) as solvent yields substituted alkenes in satisfactory yields. The reaction is formally conceived as a [2+2] cycloaddition between the aldehyde and the in situ formed ketene, followed by thermal decarboxylation of the intermediate 2-oxetanone. Ketene itself yields α,β-unsaturated acids under these reaction conditions.

ChemInform Abstract: Acid‐Catalyzed Ionic Diels‐Alder Reactions in Concentrated Solutions of Lithium Perchlorate in Diethyl Ether.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chemo- and Regioselective Conversion of Epoxides to Carbonyl Compounds in 5 M Lithium Perchlorate-Diethyl Ether Medium.

Epoxides are useful substrates in organic synthesis due to their high reactivity.1 Conversion of an epoxide to a carbonyl compound is a synthetically useful reaction, and BF3 and its etherate are the most commonly used reagents for this purpose.2 Unless there is a structural or a stereochemical bias, generally multiple products are obtained due to the lack of regioselectivity in the ring opening step. Moreover, lack of chemoselectivity among various substituted epoxides limits the synthetic utility of this reaction in multistep synthesis. In fact, no epoxide has been reported to be insensitive to BF3. Lithium and magnesium halides have been used for epoxide ring opening reaction.2-4 Recently, chemo and regioselective isomerization of epoxides to carbonyl compounds by a palladium catalyst has been reported.5 Lithium perchlorate in refluxing benzene has been reported to be a very useful reagent for the rearrangement of several epoxides as it shows higher product selectivity compared to strong Lewis acids.2,3,6 Recently, 5 M lithium perchlorate in diethyl ether (LPDE) has been shown to be an excellent medium for several synthetic transformations, and high chemo-, regio-, and stereoselectivities have been reported.7 In our efforts to use this medium for selective synthetic transformations,8,9 we have investigated the ring opening reaction of epoxides, and herein we report our results.

Chemoselective aldol type condensation of silyl enol ethers and acetals in 5 mol dm–3lithium perchlorate–diethyl ether

Acetals are efficiently and chemoselectively converted into the corresponding aldol ethers upon treatment with 1-trimethylsilyloxycyclohexene 2 in 5 mol dm–3 lithium perchlorate–diethyl ether (LPDE) at ambient temperature with moderate diastereoselectivity, whereas under the same conditions aldehydes and ketals fail to react with 2. The present method allows the acetal substitution to be carried out under neutral reaction and work up conditions. A mechanism involving the formation of an oxocarbenium ion intermediate from the acetal followed by nucleophilic addition of the silyl enol ether is proposed. The observed chemoselectivity is attributed to the mild Lewis acidity of the lithium ion in diethyl ether.

Acid Catalyzed Ionic Diels-Alder Reactions in Concentrated Solutions of Lithium Perchlorate in Diethyl Ether

Acid Catalyzed Ionic Diels-Alder Reactions in Concentrated Solutions of Lithium Perchlorate in Diethyl Ether

Ionization of the c 7 methoxy group in rapamycin by 5 M lithium perchlorate-diethyl ether

Treatment of the macrolide rapamycin (1) with 5 M LiClO 4/diethyl ether promoted ionization and elimination of the C 7 methoxy group, leading to the conjugated tetraene 2. In the presence of electron rich aromatic systems, efficient arylation at C 7 took place. C 7 arylation of rapamycin could also be achieved with Suzuki's catalyst (Cp 2HfCl 2-AgClO 4).

ChemInform Abstract: Lithium Trifluoromethanesulfonimide in Acetone or Diethyl Ether as a Safe Alternative to Lithium Perchlorate in Diethyl Ether for Effecting Diels‐Alder Reactions. Unexpected Influence of the Counterion on Exo/ Endo Selectivity.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chemoselectivity in the Michael Addition of Silyl Enol Ethers in Lithium Perchlorate-Diethyl Ether Medium. Evidence for Facile Silyl Group Transfer to Michael Acceptors

Chemoselectivity in the Michael Addition of Silyl Enol Ethers in Lithium Perchlorate-Diethyl Ether Medium. Evidence for Facile Silyl Group Transfer to Michael Acceptors

Lithium Trifluoromethanesulfonimide in Acetone or Diethyl Ether as a Safe Alternative to Lithium Perchlorate in Diethyl Ether for Effecting Diels-Alder Reactions. Unexpected Influence of the Counterion of Exo/Endo Selectivity

Concentrated solutions of lithium trifluoromethanesulfonimide in either acetone or diethyl ether constitute convenient and safe alternatives to lithium perchlorate in diethyl ether for promoting and accelerating [4+2] cycloaddition reactions.

4M lithium perchlorate-nitromethane: An efficient solvent in Diels-Alder reactions using nitroalkenes as dienophiles

Diels-Alder reactions in which nitroalkenes act as dienophiles are substantially accelerated in 4M lithium perchlorate-nitromethane solutions. This acceleration is higher than that observed when the known 5M lithium perchlorate-diethyl ether system is used.

Acid catalyzed intramolecular Diels-Alder reactions in lithium perchlorate-diethyl ether: Acid promoted migration of terminal dienes prior to [4+2] cycloaddition in conformationally restricted substrates

Use of 10 mol% camphorsulfonic acid in 5.0 M lithium perchlorate-diethyl ether to promote intramolecular Diels-Alder reactions of conformationally restricted substrates, wherein the substrates possess a terminal diene unit, gives rise to tandem diene migration - [4+2] cycloaddition.

Chemoselective Protection of Aldehydes as Dithioacetals in Lithium Perchlorate-Diethyl Ether Medium. Evidence for the Formation of Oxocarbenium Ion Intermediate from Acetals.

Aldehydes and acetals were very efficiently converted to acyclic and cyclic dithioacetals in 5 M lithium perchlorate/diethyl ether (LPDE) medium at ambient temperature in high yields. Spectroscopic and other experimental evidences strongly suggest the formation of oxocarbenium ion intermediates from acetals in 5 M LPDE which subsequently reacted with thiols to give the dithioacetals. Under the same conditions keto- nes and their acetals also reacted, albeit very slowly compared to al- dehydes and acetals, to yield dithioacetals. The difference in their reactivity was successfully employed in the chemoselective dithioace- talization of aldehydes and acetals in the presence of ketones and their acetals

Acid catalyzed intramolecular Diels-Alder reactions in lithium perchlorate-diethyl ether: Enhanced reaction rates and diastereoselectivity

The addition of 1.0–10 mol% of camphorsulfonic acid to 5.0 M lithium perchlorate in diethyl ether dramatically accelerates intramolecular Diels-Alder reactions and enhances the endo-exo selectivity.

Synthetic studies of a constrained ring didemnin analog

An asymmetric Diels-Alder reaction in the presence of 3.0 M lithium perchlorate-diethyl ether was used to generate the initial stereochemistry for a cyclohexane amino acid ( 3), a key intermediate in the preparation of a fused ring didemnin analog. This constrained ring macrocycle should provide insight into the binding site conformation of the bioactive species.

Catalysis by Lithium Perchlorate in Diethyl ether : Intramolecular Diels-Alder Reaction of Nitrotrienes

Catalysis by Lithium Perchlorate in Diethyl ether : Intramolecular Diels-Alder Reaction of Nitrotrienes

Lithium perchlorate-diethyl ether as a medium in organic addition reactions. An ersatz to high pressure methodology?

Abstract The effect of lithium perchlorate-diethyl ether solutions (LPDE) is compared to the pressure effect in several addition reactions. The results cannot be accounted for either internal pressure, or electrostriction, but point to a Lewis-acid catalytic effect, in agreement with recent propositions. It is also concluded that the high pressure methodology is generally superior to the use of LPDE to improve yields.

Diels-alder reactions enhanced diastereofacial selectivity in 5.0 M LiClO 4-Et 2O approach to the construction of the isoindolone nucleus of cytochalasans

Dienes of type 2 undergo highly diastereoselective Diels-Alder reactions with maleic anhydride in 5.0 M lithium perchlorate-diethyl ether giving rise to isobenzofurandiones which upon exposure to trifluoroacetic acid generate tetrahydroisoindolones.