Anionic conditions

A AlI lation. 1-Substitution is favored when the indole ring is deprotonated and the reaction medium promotes the nucleophilicity of the resulting indole anion. Conditions which typically result in A/-alkylation are generation of the sodium salt by sodium amide in Hquid ammonia, use of sodium hydride or a similar strong base in /V, /V- dim ethyl form am i de or dimethyl sulfoxide, or the use of phase-transfer conditions. 

Strongly acidic monomers, such as nitroethylene, can only be grafted under anionic conditions. Also, anionic grafting is useful for conventional monomers such as acrylonitrile and methylmethacrylate. In addition to the... 

Thus, for each ligand, each anion, condition, concentrations, etc. the kinetics may be different and it is worthwhile to study this, rather than rely on general statements. Simple methods are satisfactory sometimes, but more accurate methods are available and have been applied successfully to the Heck reaction [17],... 

Thus far, all examples related to the addition of nucleophiles to carbonyls involve basic (anionic) conditions. However, such conditions are not required. Recalling that a carbonyl oxygen atom possesses a partial negative charge, we recognize that under acidic conditions it can be protonated. The protonation of carbonyl groups, illustrated in Scheme 7.13, was discussed in Chapter 3. Thus, as shown in Scheme 7.14 using acetone, treatment of... 

Several examples have recently been reported of vinyl-substituted crowns that were polymerized under anionic conditions to pendant crown polymer systems <2002MM2432, 2002PLM3469, 2005PB237>. Typical examples of... 

However, the equilibrium monomer concentrations of disubstituted alkenes is measurable. The equilibrium constants for dimerization, tri-merization, and polymerization of a-methylstyrene have been determined as a function of temperature under anionic conditions [12] similar values should be obtained under cationic conditions. Unfortunately, the equilibrium position can t be determined directly under cationic conditions due to the irreversible side reactions of isomerization and indan and spirobiindan formation (Section II. A). The equilibrium monomer concentrations of isobutene and isopropenyl vinyl ethers should also be relatively high, albeit lower than those of a-methylstyrenes. However, the true equilibrium can t be reached with these monomers due to irreversible side reactions, and reliable data are therefore not available. Nevertheless, the ceiling temperature of isobutene polymerization is apparently between 50 and 150° C. 

Perflnoroalkenes are significant industrial starting materials, of which the simplest and most important is TFE. This reactive alkene can be reacted, mainly nnder free radical or anionic conditions, to yield a variety of saturated addition products (Scheme 1). TFE displays versatile polymerization and copolymerization applications. ... 

Under anionic conditions, the ring opening follows an Sn2 mechanism. Thus, the ring opening of The nng opening of epoxides. , ., o r o. , , ... 

The (pivaloyloxy)methyl group in quinazolin-4(3//)-ones 11, which is frequently used to protect the N3 atom from alkylation under anionic conditions, is conveniently removed by mild alkaline hydrolysis. ... 

These four examples of the successful application of the Julia coupling in natural product synthesis indicate the sensitivity of various substrates to the anionic conditions. The solutions, interchanging the aldehyde and sulfone portions, modification of the substrate or altering the reductive elimination conditions, are all techniques that can enable the successful use of the Julia coupling for ( )-alkene synthesis. 

Figure 6J.0. Separation of oxaiate, thiosulfate and other anions. Conditions Allsep anion column 100 X 4.6 mm, 4 mMphthalicacid.pH 4.2,1.0 mL/minat35 conductivity detector (Courtesy Alltech).

Figure 6.11. Separation of weak acid anions. Conditions Alltcch Anion/R column, sodium hydroxide/ sodium benzoate eluent, 1.5 mL/min, conductivity detection. Hydroxide is the primary eluent for this separation and the weak acid anions are detected with indirect conductivity. A small amount of benzoate is added to speed the elution of the anions (Courtesy Alltcch).

Figure 10.16. Separation of 17 inorganic and organic anions. Conditions same as Fig. 10.15. Peaks I = bromide 2 = nitrate 3 = chromate 4 = iodide 5 = molybdate 6 = phthalate 7 = 1,2,3-tricarboxylate 8 = 1,2-benzenedisulfonate 9 = terephthalate 10 = isophthalate 11 = benzoate 12 = p-toluenesulfonate 13 = 1,2,5-tricarboxylatc 14 = 2-nathphalenesulfonate 15 = 1-naphthalencsulfonate 16 = 3,5-dihydrox-ybenzoato 17 = 2,4-dihydroxybenzoate x = unidentified impurity.

Figure 8.21 Schematic representations of normal and modulated crystal structures and diffraction patterns (a) a normal superlattice, formed by the repetition of an anion substitution (b) part of the diffraction pattern of (a) (c) a crystal showing a displacive modulation of the anion positions (d) a crystal showing a compositional modulation of the anion conditions, (the change in the average chemical nature of the anion is represented by differing circle diameters) (e) part of the diffraction pattern from (c) or (d) (f) a modulation wave at an angle to the unmodulated component (g) part of the diffraction pattern from (f). Metal atoms are represented by shaded circles and non-metal atoms by open circles...

An appreciation of the ability of 48 to attain appreciable levels of double diastereoselection when reacted with chiral (racemic) vinyl organocerium reagents had earlier been gained in this laboratory [32]. Consequently, it occasioned no surprise to observe that 49 [33] adds to this bicyclic ketone with customary endo stereoselectivity to deliver 50 and 51 in a relative ratio of 92 8. The major product, easily purified by chromatographic means, was smoothly isomerized to 52 under anionic conditions at room temperature. For structural reasons, this sigmatropic change is required to proceed via a boat-like transition state. The all-... 

The first factor in the left-hand side is greater than unity and the second one is less than unity. Hence, the realization of conditions for the dynamic adsorption layer formation is possible both with electrostatic retardation of the adsorption and without, depending on the system parameters. Note that condition (9.35) can be fulfilled only for multiple-charged anions. Conditions considered in the present section correspond to the situation where the dynamic... 

Penelle. J. Xie. T. Ring-opening polymerization of diisopropyl cyclopropane-1.1 -dicarboxylate under living anionic conditions A kinetic and mechanistic study. Macromolecules 2000.33 (13). 4667-4672... 

Penelle, J. and Xie, T, Ring Opening Polymerization of Diisopropyl Ciclopro-pane-1,1 Dicarboxylate under Living Anionic Conditions A Kinetic and Mech-anicistic Study, Macromolecules, 33, 4667, 2000. 

Figure 6.12 Separation of oxalate, thiosulfate and other anions. Conditions Allsep anion column 100x4.5 mM, 4 mM phthalic acid, pH 4.2, 1.0 ml min at 35 °C, conductivity detector (courtesy Alltech).

Figure11.17 Separation of inorganic and organic anions. Conditions 100 mM tetra-butylammonium acetate electrolyte at pH 5.5 -15 kV. Peaks in order of increasing t , nitrite, nitrate, iodide, 1,2-benzenedisulfonate.

Several amino-styrenic monomers are known for example see 19C—23C in Figure 38. The simplest of these, the primary amine species 4-vinylaniline (or 4-aminostyrene), 23C, is susceptible to polymerization imder conventional free radical conditions, as are 19C-22C. For example, the UV-induced graft polymerization of 23C from a Si surface was recently disclosed (218). These monomers tend to polymerize most effectively in aqueous media in their hydrochloride salt form. Given the reactive nature of the amine functionality in 23C it is also a suitable precursor for the synthesis of novel amide-based styrenics (219). The controlled polymerization of 19C, 20C, and 22C, under classical anionic conditions is also possible (220,221). For example, AB diblock copol5uners of22C with styrene can be prepared at -78°C, in THF using cumyl potassium as the initiator with 22C being polymerized first. Near-monodisperse w-butyl quats of 19C, 20C, and 22C have also been reported. These were prepared by the post-polymerization modification of polymers from 19C, 20C, and 22C with R-butyl bromide (220). 

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