Perchlorate, lithium reaction

Rather different experimental results were obtained by de la Mare et a/.208, 209, who studied chlorination by hypochlorous acid in 51, 75 and 98 % aqueous acetic acid. With the latter medium, the chlorination of anisole or m-xylene (at an unspecified temperature) was independent of the concentration of aromatic, and catalysed by perchloric acid to a much greater extent than an equimolar amount of lithium perchlorate the reaction was also catalysed by the base, sodium acetate. The reactive species was postulated as chlorine acetate produced... 

Reaction (21) (X = Cl, I, OAc) has been studied by Abraham and Hogarth31 using acetonitrile as solvent. Rate coefficients and activation parameters are in Table 21. Tetra-n-butylammonium perchlorate and also lithium perchlorate accelerate reaction (21) (X = Cl) application of equation (22) yielded values for Z2d of 0.652 (Bu"4NC104) and 0.674 (LiC104). If c/ is taken as 3.1 A, as before, these values correspond to 0.46 and 0.47 for Z. Although Z is much less than observed when hydroxylic solvents are used (see Table 19), Abraham and... 

If the reactions are carried out in a nitrile as solvent, rather than dichloromethane, using triflic acid as catalyst, a modified Ritter reaction takes place, and the intermediate nitrilium ion traps the liberated amine, forming an amidine (Scheme 67). In an earlier reaction cf. Scheme 67) the lithium perchlorate catalyzed reaction of sulfenyl chlorides with alkenes in the presence of nitriles had also given l-amido-2-sulfenyl adducts. Ritter products are also obtained in good yields by anodic oxidation (Pt or C, 1.2-1.4 V) of disulfides in acetonitrile, in the presence of excess alkene, using B114NBF4 as supporting electrolyte (Scheme 68). ... 

Experimentally it has been shown that the threshold pressure at which combustion instability can be induced artificially in composite proplnts by pulsing is a function of the burning rate of the proplnt (in a motor size of 5-inch diameter and 40-inch length) (Ref 45). This relationship is shown in Figs 17 and 18 for both aluminized and non-aluminized composite proplnts. It was also found that potassium perchlorate, lithium perchlorate and AN proplnts were resistant to this induced instability. Since AP composites were the only proplnts, other than double-base, which were driven unstable, the rate controlling reactions and response function are those related to AP decompn and perhaps the diffusion flame between oxidizer and binder... 

Reactions of tetra-alkyltin compounds with mercury(n) iodide in 96% methanol, as with mercury(n) chloride, - are bimolecular. The variation of rate constant with alkyl group suggests an open S 2 transition state (5). Further evidence for this mechanism is provided by the variation of rate constant with solvent Y values for the particular case of the tetraethyltin compound reacting with mercury(n) chloride in a range of aqueous methanol mixtures. Solvent effects in this last series of reactions have been separated into initial state and transition state contributions by the determination of heats of solution and of transfer of the reactants. The effect of added lithium perchlorate on reaction rates for tetra-alkyltin compounds with mercury(ii) iodide again indicates bimolecular electrophilic... 

Lenzi and Rapson (134) further studied the reaction of Eq. 69 in 2.32M and 5.0W sulfuric acid in the presence of sodium perchlorate, potassium perchlorate, lithium nitrate, sodium nitrate, and potassium nitrate. These salts increased the rate of the reaction and decreased the inhibiting effect of chlorine. These conditions were attributed to an effective increase in the acidity, due to the decrease in "free" water which results upon the addition of the ionic salts. This interpretation enabled Lenzi and Rapson to explain the very high order of the reaction with respect to the concentration of sulfuric acid. One additional complication is that Cl03 does not seem to affect the rate of chlorous acid disproportionation (120), as would be required by Eq. 81. 

Allylic alcohols derived from 1,4-dioxene can be used to alkylate TMSOF in the presence of lithium perchlorate. The reaction proceeds through an oxocarbenium ion, with one example exhibiting an equal amount of side product arising from the alkylation at the tertiary carbon (eq 18). ... 

In 1990 Grieco introduced a 5 molar solution of lithium perchlorate as a new medium for the Diels-Alder reaction that is capable of inducing not only an improvement of the rate but also of the endo-... 

The method described here gives higher yields of the macrocyclic tetraethers and allows the product from furan and cyclohexanone to be formed directly in 5-10% yield, whereas this product was previously obtained only by an indirect route. The added lithium perchlorate undoubtedly accelerates the reaction, since after short reaction times the product was isolated in 20% yield when the salt was present and in only 5% yield when the salt was absent. The lithium cation is presumably acting as a template which coordinates with the oxygen atoms of... 

These reactions are presumed to occur through aroyl triflate intermediates which dissociate to aiyl acylium ions. Lithium perchlorate and scandium triflate also promote acylation. ... 

A study of the Diels-Alder reaction was carried out by Earle et al. [42]. The rates and selectivities of reactions between ethyl acrylate (EA) and cyclopentadiene (CP) in water, 5 m lithium perchlorate in diethyl ether (5 m EPDE), and [BMIM][PE(3] were compared. The reactions in the ionic liquid [BMIM][PE(3] were marginally faster than in water, but both were slower than in 5 m EPDE [42, 43] (see Table 5.1-1 and Scheme 5.1-18). It should be noted that these three reactions give up to 98 % yields if left for 24 hours. The endo. exo selectivity in [BMIM][PE(3] was similar to that in 5 M EPDE, and considerably greater than that in water (Table 5.1-1). 

The next major obstacle is the successful deprotection of the fully protected palytoxin carboxylic acid. With 42 protected functional groups and eight different protecting devices, this task is by no means trivial. After much experimentation, the following sequence and conditions proved successful in liberating palytoxin carboxylic acid 32 from its progenitor 31 (see Scheme 10) (a) treatment with excess 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) in ie/t-butanol/methylene chloride/phosphate buffer pH 7.0 (1 8 1) under sonication conditions, followed by peracetylation (for convenience of isolation) (b) exposure to perchloric acid in aqueous tetrahydrofuran for eight days (c) reaction with dilute lithium hydroxide in H20-MeOH-THF (1 2 8) (d) treatment with tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran first, and then in THF-DMF and (e) exposure to dilute acetic acid in water (1 350) at 22 °C. The overall yield for the deprotection sequence (31 —>32) is ca. 35 %. 

Eq. (3), with lithium diisopropylamide (LDA) to a lithiospecies and in its subsequent reaction with C02 affording via the corresponding 4-carboxylic acid its ethyl ester 59. In the alternative version perchlorate 48e is electro-chemically reduced in acetonitrile to an anionic species that was converted either to a 3 1 mixture of isomers 56 (R = f-Bu) and 60 or to 4//-thiopyran 56 (R = PhCH2) with f-BuI or PhCH2Br, respectively (90ACS524). The kinetics of the benzylation procedure was followed by cyclic voltammetry [88ACS(B)269]. 

The equatorial selectivity observed with organolithium reagents is enhanced in diethyl ether as the reaction solvent by the addition of lithium perchlorate (Table l)12. I3C-NMR studies47 indicate that the formation of a complex between lithium perchlorate and the carbonyl group, which also leads to a dramatic enhancement of the rate of the addition reaction, accounts for the increased diastereoselectivity. 

A similar stereospecific conjugate addition to epoxysulfone 323 was also observed416. When this reaction of 323 was carried out with methyllithium at — 78 °C dichloromethane-diethyl ether (1 1) in the presence of lithium perchlorate, compounds 324 and 325 were obtained in a ratio of 95 5. On the other hand, in the treatment of 323... 

During 1989-93 lithium perchlorate iethyl ether (LiC104 EtiO, LP-DE) was studied as a reaction medium in organic synthesis when it was observed that cycloadditions, sigmatropic rearrangements, Michael additions and aldol condensations carried out in LP-DE occurred quickly and selectively under mild reaction conditions [33]. In addition, LP-DE allowed the reaction and subsequent work-up to be carried out under essentially neutral conditions. 

LP-DE has a weaker catalytic activity than BF3-Et20, AICI3 and TiCU because the Lewis acidity of the lithium cation is moderated by complex-ing with diethyl ether and perchlorate anion [37], but it becomes a highly oxophilic Lewis acid when concentrated solutions are used [38]. The concentration of LP-DE is therefore sometimes essential for the success of the reaction. 

Lithium perchlorate in nitromethane (LP-NM) is sometimes a more effective reaction medium than LP-DE for certain Diels-Alder reactions. The cycloaddition of 2,3-dimethylbutadiene with nitrostyrenes (Scheme 6.24) occurs with low... 

Dramatic rate acceierations of Dieis-Aider reactions in 5m lithium perchlorate-diethyl ether the cantaridin problem reexamined [34]... 

Acid catalyzed intramolecular Diels-Alder reactions in lithium perchlorate-diethyl ether acid promoted migration of terminal dienes prior to [4 + 2] cycioaddition in conformationally restricted substrates [101]... 

Acid catalyzed ionic Diels-Alder reactions in concentrated solutions of lithium perchlorate in diethyl ether [43]... 

The cause of the rate acceleration by diethyl ether solutions of lithium perchlorate in organic reactions. Application to high pressure synthesis [35c] o O,... 

Lithium catalyzed hetero-Diels-Alder reactions. Cyclocondensation of N-protected ot-amino aldehydes with 1-methoxy-3-fert-butyldimethylsilyloxybutadiene in the presence of lithium perchlorate [104]... 

Diels-Alder reactions of quinones generated in situ by electrochemical oxidation in lithium perchlorate-nitromethane [105]... 

Catalysis by lithium perchlorate in dichloromethane Diels-Alder reactions and 1,3-Claisen rearrangements [100]... 

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 [47]... 

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