Quatemization reaction

The quatemization reaction of the thiazole nitrogen has been used to evaluate the steric effect of substituents in heterocyclic compounds since thiazole and its alkyl derivatives are good models for such study. In fact, substituents in the 2- and 4-positions of the ring only interact through their steric effects (inductive and resonance effects were constant in the studied series). The thiazole ring is planar, and the geometries of the ground and transition states are identical. Finally, the 2- and 4-positions have been shown to be different (259. 260). 

The importance of the solvent, in many cases an excess of the quatemizing reagent, in the formation of heterocyclic salts was recognized early. The function of dielectric constants and other more detailed influences on quatemization are dealt with in Section VI, but a consideration of the subject from a preparative standpoint is presented here. Methanol and ethanol are used frequently as solvents, and acetone,chloroform, acetonitrile, nitrobenzene, and dimethyl-formamide have been used successfully. The last two solvents were among those considered by Coleman and Fuoss in their search for a suitable solvent for kinetic experiments both solvents gave rise to side reactions when used for the reaction of pyridine with i-butyl bromide. Their observation with nitrobenzene is unexpected, and no other workers have reported difficulties. However, tetramethylene sulfone, 2,4-dimethylsulfolane, ethylene and propylene carbonates, and salicylaldehyde were satisfactory, giving relatively rapid reactions and clean products. Ethylene dichloride, used quite frequently for Friedel-Crafts reactions, would be expected to be a useful solvent but has only recently been used for quatemization reactions. ... 

The quinazoline ring also gives some anomalous quatemization reactions, which presumably reflect the influence of the unusual 3,4-bond. 3-Methyl-4-quinazolone (71 Y = O) and, more... 

Of the four possible oxazolopyridines, two have been studied with respect to quatemization reactions. Frazer and Tittensor prepared 2-alkyl- and 2-aryl-oxazolo[4,5-c]pyridines (105 Y = H) and converted them into methiodides, the structures of which have not been determined. Subsequently Takahashi et al. prepared the corresponding 5-methyl (105 Y = Me) and 2-methyl-5-nitro compounds and... 

Pyridines.149 References are made to quatemization reactions of pyridines in nearly all sections of Part I. A very extensive series of papers dealing with pyridinium ions and fused ring pyridinium ions, their preparations and properties is available.150... 

Annulation of a five-membered aza ring to a benzo ring generally leads to rate retardation in N-quatemization reactions similar in magnitude to that for six-membered rings. Exceptions are known ... 

In the present study, [N-Alk-Pz](TCNQ)m and [N-Alk-Pz](MTCNQ)m salts have been synthesized, with Aik for CnH2n+i n = 1, 2,...5 m 1,2. Aldrich- KodxLCQ pyrazine was used without any additional purification, while TCNQ and MTCNQ were refined by vacuum zone sublimation. Iodide alkyls were synthesized by the reaction of corresponding alcohols with phosphate tri-iodide followed by a distillation in inert atmosphere. To obtain alkylpyrazinium iodides, the quatemization reaction was used ... 

The following section focuses on the quatemization reaction of 1-alkylimidazoles since these are the most commonly used starting materials for ionic liquids and have dominated ionic liquids research over the last twenty years. However, the general method for the quatemization reaction is similar for pyridines [13], isoquinolines [14], 1-methylpyrrolidine [15], trialkylamines [16], phosphines [17] and sulfides [18]. 

Imidazo[2, r 2,3]thiazolo[4,5-f>]quinoxalines were obtained in one step from imidazole precursors <02IJH257>. Intramolecular quatemization reactions of either 158 or 159 ultimately afforded quinoxalines 161 from substituted acetanilides 160 <02JCS(P1)790>, and a two-step... 

B[18]-N204 (4) turned out to be a very useful compound for testing the double-quatemization reactions, since it possesses four aromatic protons which are well separated in the lH NMR. Thus, the structures of the products can be easily established by means of NMR spectroscopy. Representative example of this double-quatemi-zation method is illustrated in Scheme 10. For preparative performance, e.g. a 1 1 mixture of 4 and bis(2-iodoethyl)ether (41) (ca, 0.08 M solution in acetone) was exposed to the pressure of 10 kbar 40) for 20 h. The bisquaternary salt 42 precipitated during the reaction course quantitatively. 

Very successful results in the synthesis of simple cryptands stimulated more systematic studies in this field. First of all, it was interesting to test the influence of the length of the bridging component on the yield obtained for the double-quatemization reaction... 

IX. Obtaining Relative Rate Constants for Quatemization Reactions by... 

Xiang L, Zhang ZN, Yu P et al (2008) In situ cationic ring-opening polymerization tmd quatemization reactions to confine ferricyanide onto carbon nanotubes a general approach to development of integrative nanostructiued electrochemical biosensors. Antil Chem 80 ... 

However, this three-step process is really time-consuming and tedious, especially due to the quatemization reaction that involves inefficient spin-coating followed by vacuum treatment in an oven at 110°C, to obtain full chromophore coverage. To enhance the process efficiency and speed, a greatly improved all- wet-chemical ... 

Poly(styrene-co-N-vinylbenzyI-N -inethyl-4,4 -bipyridine) di-chloiide (2). N-Methyl-4,4 -bipyridine was attached to chloromethylated polystyrene via a quatemization reaction. Chloromethylated polystyrene (1.00 g) and 1.26 g of N-methyl-4,4 -bipyridine were dissolved in 100 mL of CHCI3 and 100 mL of CH3CN. The pale yellow solution was refluxed for 72 h, after which much of the solvent was removed. An ion-exchange column was prepared... 

Preparation. - A range of 1,3-dithianylphosphonium salts (218) has been prepared in the course of further studies of sulfur lone pair anomeric effects in these systems.Conventional quatemization reactions have been used in the synthesis of the salt (219) and a range of polymer-supported phosphonium salts (220). A new efficient route to salts of the type (221) has been developed. The of>-azolylalkylphosphonium salts (222) are readily accessible from the reactions of the corresponding a>-bromoalkylphosphonium salts and azoles. Routes to vinylphosphonium salts, e.g., (223), continue to be explored, and their reactivity utilised in the synthesis of phosphonium salts bearing heterocyclic substituents, e.g., (224). The betaine (225) has been... 

The quatemization reaction should be carried out either in a system that has been degassed and sealed under nitrogen, or else under a flow of inert gas such as nitrogen. Furthermore the reaction temperature should be kept as low... 

Poly(aryl ether ketone)s with two quaternary ammonium groups on pendant phenyls can be synthesized by a bromination followed by a quatemization reaction with trimethylamine [72]. Such polymers play an important role in the preparation of direct methanol fuel cells. 

In the case of the aza derivatives of the 3fT-indole or indolenine ring, however, the two nitrogen atoms would be expected to be more nearly equivalent, indolenine itself being easily converted into its quatmiary salt. The quatemization reactions of 1,7-, 1,6-, and l,4-diaza-3, 3-dimethyl-3fl -indenes have recently been studied by Ficken and Kendall. 

Various synthetic methods for ILs have been reviewed in detail [14]. In order to provide a specialized capability for an IL, functional groups need to be present in the cation or anion. Such functionalized ILs are commonly termed task-specific ionic liquids (TSlLs) [15]. Generally, the IL cation is the favored functionalization site because of the wide variety of available natural products that already contain the desired moieties. These compounds are usually transformed into cations via a quatemization reaction between a nucleophilic group such as an amine, V-hetero-cycle, phosphine, and an alkyl halide [16]. 

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