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Aprotic

CH3)2N]3P0. M.p. 4°C, b.p. 232"C, dielectric constant 30 at 25 C. Can be prepared from dimethylamine and phosphorus oxychloride. Used as an aprotic solvent, similar to liquid ammonia in solvent power but easier to handle. Solvent for organolithium compounds, Grignard reagents and the metals lithium, sodium and potassium (the latter metals give blue solutions). [Pg.203]

Volpin called the CH3COCI lAlCk complex an aprotic superacid. The results indicate that the acetyl cation is activated by further 0-complexation with a second molecule of AIX3 (the equivalent of protonation or protosolvation). [Pg.194]

As indicated in the general scheme below, butatrienes are the first products from base-induced 1,4-elinination of hydrogen and a suitable leaving group. The butatriene in general very readily undergoes isomerization into enynes, if sufficiently "acidic" protons are available (see Chapter 11 in Ref. 3a). In aprotic media cumulenic ethers are fixed as their lithio derivatives if an excess of alkyllithium is applied... [Pg.115]

Esters are alkylated in the presence of strong bases in aprotic solvents. A common combination is LDA in tetrabydrofuran at low temperatures. Equimolar amounts of base are sufficient and only the mono-carbanion Js formed. After addition of one mole of alkyl halide the products form rapidly, and no dialkylation, which is a problem in the presence of excess base, is possible. Addition of one more mole of LDA and of another alkyl halide leads to asymmetric dialkylation of one or-carbon atom in high yield (R.J. Cregge, 1973). [Pg.22]

An interesting case are the a,/i-unsaturated ketones, which form carbanions, in which the negative charge is delocalized in a 5-centre-6-electron system. Alkylation, however, only occurs at the central, most nucleophilic position. This regioselectivity has been utilized by Woodward (R.B. Woodward, 1957 B.F. Mundy, 1972) in the synthesis of 4-dialkylated steroids. This reaction has been carried out at high temperature in a protic solvent. Therefore it yields the product, which is formed from the most stable anion (thermodynamic control). In conjugated enones a proton adjacent to the carbonyl group, however, is removed much faster than a y-proton. If the same alkylation, therefore, is carried out in an aprotic solvent, which does not catalyze tautomerizations, and if the temperature is kept low, the steroid is mono- or dimethylated at C-2 in comparable yield (L. Nedelec, 1974). [Pg.25]

Selective reduction of a benzene ring (W. Grimme, 1970) or a C C double bond (J.E. Cole, 1962) in the presence of protected carbonyl groups (acetals or enol ethers) has been achieved by Birch reduction. Selective reduction of the C—C double bond of an a,ft-unsaturated ketone in the presence of a benzene ring is also possible in aprotic solution, because the benzene ring is redueed only very slowly in the absence of a proton donor (D. Caine, 1976). [Pg.104]

The most commonly used protected derivatives of aldehydes and ketones are 1,3-dioxolanes and 1,3-oxathiolanes. They are obtained from the carbonyl compounds and 1,2-ethanediol or 2-mercaptoethanol, respectively, in aprotic solvents and in the presence of catalysts, e.g. BF, (L.F. Fieser, 1954 G.E. Wilson, Jr., 1968), and water scavengers, e.g. orthoesters (P. Doyle. 1965). Acid-catalyzed exchange dioxolanation with dioxolanes of low boiling ketones, e.g. acetone, which are distilled during the reaction, can also be applied (H. J. Dauben, Jr., 1954). Selective monoketalization of diketones is often used with good success (C. Mercier, 1973). Even from diketones with two keto groups of very similar reactivity monoketals may be obtained by repeated acid-catalyzed equilibration (W.S. Johnson, 1962 A.G. Hortmann, 1969). Most aldehydes are easily converted into acetals. The ketalization of ketones is more difficult for sterical reasons and often requires long reaction times at elevated temperatures. a, -Unsaturated ketones react more slowly than saturated ketones. 2-Mercaptoethanol is more reactive than 1,2-ethanediol (J. Romo, 1951 C. Djerassi, 1952 G.E. Wilson, Jr., 1968). [Pg.165]

In contrast to oxidation in water, it has been found that 1-alkenes are directly oxidized with molecular oxygen in anhydrous, aprotic solvents, when a catalyst system of PdCl2(MeCN)2 and CuCl is used together with HMPA. In the absence of HMPA, no reaction takes place(100]. In the oxidation of 1-decene, the Oj uptake correlates with the amount of 2-decanone formed, and up to 0.5 mol of O2 is consumed for the production of 1 mol of the ketone. This result shows that both O atoms of molecular oxygen are incorporated into the product, and a bimetallic Pd(II) hydroperoxide coupled with a Cu salt is involved in oxidation of this type, and that the well known redox catalysis of PdXi and CuX is not always operalive[10 ]. The oxidation under anhydrous conditions is unique in terms of the regioselective formation of aldehyde 59 from X-allyl-A -methylbenzamide (58), whereas the use of aqueous DME results in the predominant formation of the methyl ketone 60. Similar results are obtained with allylic acetates and allylic carbonates[102]. The complete reversal of the regioselectivity in PdCli-catalyzed oxidation of alkenes is remarkable. [Pg.30]

Nevertheless, they are stable to standard work-up and purification methods. The benzenesulfonyl group can be introduced using base and an aprotic solvent[3] or under phase transfer conditions[4], Table 9.2 gives some representative examples of acylation and sulfonylations. [Pg.92]

Use of aprotic solvents increases the quantity of exocyclic N-alkylation the potassium salt of A -(2-thiazolyDcaTbamate heated in DMF with 2-phthalimidoethyl bromide gives predominantly exocyclic N-alkylation (70% 47a, 30% 47b) (Scheme 34) (131). [Pg.35]

In aprotic conditions acetic anhydride sodium acetate induces formation of a fused ring through an intra molecular condensation. It results in a pyrrolo[2,l-fc]thiazole (39), which constitutes an interesting intermediate for the synthesis of dyes (Scheme 18) (40). [Pg.36]

Solvent Effects on the Rate of Substitution by the S 2 Mechanism Polar solvents are required m typical bimolecular substitutions because ionic substances such as the sodium and potassium salts cited earlier m Table 8 1 are not sufficiently soluble m nonpolar solvents to give a high enough concentration of the nucleophile to allow the reaction to occur at a rapid rate Other than the requirement that the solvent be polar enough to dis solve ionic compounds however the effect of solvent polarity on the rate of 8 2 reactions IS small What is most important is whether or not the polar solvent is protic or aprotic Water (HOH) alcohols (ROH) and carboxylic acids (RCO2H) are classified as polar protic solvents they all have OH groups that allow them to form hydrogen bonds... [Pg.346]

The large rate enhancements observed for bimolecular nucleophilic substitutions m polai aprotic solvents are used to advantage m synthetic applications An example can be seen m the preparation of alkyl cyanides (mtiiles) by the reaction of sodium cyanide with alkyl halides... [Pg.347]

Rate increases with increasing po larity of solvent as measured by its dielectric constant e (Section 8 12) Polar aprotic solvents give fastest rates of substitution solvation of Nu IS minimal and nucleophilicity IS greatest (Section 8 12)... [Pg.356]

HCN(CH3)2 DMF IS a polar aprotic solvent (Section 8 12) and an excellent medium for Sm2 reactions... [Pg.930]

This IS an example of an Sn2 reaction in a polar aprotic solvent... [Pg.1008]

Aprotic solvent (Section 8 12) A solvent that does not have easily exchangeable protons such as those bonded to oxy gen of hydroxyl groups... [Pg.1276]

The equation above suggests that one approach would be to use a pore Hquid that has a low surface tension. Indeed, two-step acid—base or acid—acid catalyzed sHica gels have been made, aged in ethanol or water, washed with various aprotic solvents, and finally evaporatively dried at 323 K for 48 hours and then at 383 K for 48 hours (43). The aprotic solvents used and their corresponding surface tension in N/m at room temperature (shown in... [Pg.4]

A brief review has appeared covering the use of metal-free initiators in living anionic polymerizations of acrylates and a comparison with Du Font s group-transfer polymerization method (149). Tetrabutylammonium thiolates mn room temperature polymerizations to quantitative conversions yielding polymers of narrow molecular weight distributions in dipolar aprotic solvents. Block copolymers are accessible through sequential monomer additions (149—151) and interfacial polymerizations (152,153). [Pg.170]

The preparation of fluoroaromatics by the reaction of KF with perhaloaromatics, primarily hexachloroben2ene, has received considerable attention. Two methods were developed and include either the use of an aprotic, polar solvent, such as /V-methy1pyrro1idinone (8), or no solvent (9). These methods plus findings that various fluoroaryl derivatives are effective fungicides (10) prompted development of a commercial process for the production of polyfluoroben2enes (11). The process uses a mixture of sodium and potassium fluorides or potassium fluoride alone in aprotic, polar solvents such as dimethyl sulfoxide or sulfolane. [Pg.267]


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See also in sourсe #XX -- [ Pg.762 , Pg.798 , Pg.811 , Pg.813 , Pg.829 ]

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See also in sourсe #XX -- [ Pg.762 , Pg.798 , Pg.811 , Pg.813 , Pg.829 ]

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Acceleration of Base-Catalysed Reactions in Dipolar Aprotic Solvents

Acetone aprotic, polar

Acetonitrile polar, aprotic

Acid in dipolar aprotic solvents

Acid-base concepts aprotic acids

Acids and Bases in Reactive Aprotic Solvents

Ammonia dipolar aprotic solvent

And aprotic solvents

Apolar and aprotic solvent

Aprotic Electrolytes in Li-Air Batteries

Aprotic acetonitrile

Aprotic acid

Aprotic chloroform

Aprotic conditions

Aprotic dichloromethane

Aprotic dipolar dissolvent

Aprotic dipolar protophilic solvents

Aprotic dipolar protophobic solvents

Aprotic equilibrium

Aprotic inert solvents

Aprotic ionic liquids

Aprotic media

Aprotic nitrating agent

Aprotic nucleophilic solvents

Aprotic organic cations

Aprotic organic solvents

Aprotic organic superacids

Aprotic oxidizing agents

Aprotic polar solvents, Table

Aprotic solvent

Aprotic solvents Aromatic solvent shifts

Aprotic solvents acetonitrile

Aprotic solvents alkene hydrogenation

Aprotic solvents anion activity

Aprotic solvents compounds

Aprotic solvents dimethylformamide

Aprotic solvents dipole moments

Aprotic solvents electrolytes

Aprotic solvents hexafluorophosphate

Aprotic solvents nitro compound reduction

Aprotic solvents purity

Aprotic solvents tetrabutylammonium

Aprotic solvents thermodynamic measurements

Aprotic solvents, cross-conjugated

Bamford-Stevens reaction aprotic

Bases. in polar aprotic solvents

Batteries aprotic

Bimolecular substitution reactions in protic and dipolar aprotic solvents

Carbon dioxide aprotic conditions

Carboxylic acid derivatives in aprotic solvents

Condensation aprotic

Cyclic voltammetry aprotic solvents

Diazotization aprotic

Dimethyl aprotic, polar

Dimethyl as solvent, aprotic, pola

Dimethyl sulfate aprotic, polar

Dimethyl sulfoxide aprotic, polar

Dimethyl sulfoxide as polar aprotic solvent

Dipolar aprotic

Dipolar aprotic and protic solvents, rates

Dipolar aprotic and protic solvents, rates of bimolecular substitution reactions

Dipolar aprotic solvent cation solvation

Dipolar aprotic solvents

Dipolar aprotic solvents electrolytes

Dipolar aprotic solvents recovery

Dipolar aprotic solvents sulfolane

Electrodes aprotic

Electrolyte aprotic

Electrolytes Based on Aprotic Nonaqueous Solutions

Electrolytes Based on Aprotic Solvents

Electrolytes aprotic organic

Formal Electrode Potentials Aprotic Solvents

In aprotic media

Ketalization under aprotic conditions benzaldehyde dimethyl acetal

MICHAEL ADDITION, APROTIC

Methylene chloride aprotic

Michael addition under aprotic conditions

Nitrogen aprotic

Nonpolar aprotic solvents

Nucleophilicity in aprotic solvents

Nucleophilicity polar aprotic solvents

Polar aprotic organic solvents

Polar aprotic solvent Sn2 reaction and

Polar aprotic solvent effects

Polar aprotic solvent. See

Polar aprotic solvents poly 2-

Polar aprotic solvents, enol stability

Polar aprotic solvents, reverse

Polar protic and aprotic solvents

Polarity aprotic solvents

Polarograph aprotic solvents

Polymer supported dipolar aprotic solvent

Potential in aprotic solvents

Precursors aprotic

Protic and Dipolar Aprotic Solvent Effects on the Rates of Sn Reactions

Protic versus aprotic solvents

Reactions in Aprotic Solvents

Reference Electrodes for Use in Polar Aprotic Solvents

Solvent aprotic solvents

Solvent dipolar aprotic solvents

Solvent protic, aprotic

Solvent types polar aprotic

Solvent, polar aprotic protic

Solvents aprotic, substitution

Solvents aprotic, substitution, nucleophilic

Solvents, acceptor number aprotic

Solvents, acidic aprotic

Solvents, acidic dipolar aprotic

Solvents, amphiprotic aprotic

Solvents, aprotic spectrometry

Solvents, nonaqueous aprotic

Solvents, polar aprotic

Substitution reactions, bimolecular in protic and dipolar aprotic

Superacids aprotic

Very polar aprotic solvents

Wittig reaction polar aprotic solvents

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