Quaternization special

Isoxazolium salts can be prepared by reaction with alkyl iodides or sulfates, although the low basicity of isoxazoles and their sensitivity to nucleophilic attack may necessitate special care. Isoxazolium salts containing bulky Af-substituents can be prepared by the reaction of isoxazoles with alcohols in the presence of perchloric acid. For example, the reaction of 3,5-dimethylisoxazole (53) with some alcohols in the presence of 70% perchloric acid gave isoxazolium salts, (54a) in 29%, (54b) in 57% and (54c) in 82% yield 79AHC(25)147, 68JOC2397). Attempts to quaternize 3,5-dimethyl-4-nitroisoxazole failed 71JCS(B)2365). 

A special type of ammonio group is represented by 4-( 1 -pyridinium)-pyridine and other azinium analogs. Such products often result from self-quaternization of highly reactive derivatives. A -(4-Pyridyl)-and A -(3-nitro-4-pyridyl)-pyridinium chloride hydrochlorides (121) react with aniline, chloride ion, and water to give 4-substituted pyridines plus pyridine. l-(2-Quinolyl)- and l-(4-quinolyl)-pyridinium salts undergo 2- and 4-substitution, respectively, with amines, anilines, hydroxylamine, phenols, alkoxides, mercaptans, and chloride... 

Heteroaryl groups are present in the 4-pyridyl-ethynyl compounds81,99,100 and their extended variants with C=C-C6H4-C=C-pyr-4 ligands.81,99 These compounds can be quaternized with Mel or coordinated to a metal complex at their terminal pyridyl functions to give species addressed as molecular rods or molecular wires.81,99 Similar reactions were carried out with 3-phenanthrolinyl-ethynyl complexes,62 and special examples are also known with R based on calixarenes.51... 

In the course of further investigations, charged groups were specially incorporated into PAA networks by copolymerization of acrylamide (AA) with sodium methacrylate (SMA) [10] and also with IV-acryloylsuccinimide, which is easily hydrolyzed in an aqueous medium [11]. Later, the networks of PAA containing cationic ammonium groups [12-14] and quaternized pyridine groups [15] were investigated. 

All these special cases involve benzologs with an ortho quinonoid structure. But even this pattern is not universal, a deviation being 2-methylindazole (40), which quaternizes 2.2 times more slowly than its parent compound 1-methylpyrazole (37).122 Indeed, except for the molecules just considered and 1,2-benzisothiazole,122 benzo-fusion is rate retarding. Thus, 1,2-benzisoxazole (indoxazene, 39), reacts 3.2 times, and 1-methylindazole (39) 7.1 times, more slowly than their parent compounds.122 Fusing a benzene ring onto an azole where the heteroatoms are situated 1,3 leads to decreases in rate constants by factors of 5.0, 6.3, and 6.8, respectively, when X of 38 is NMe, S, and O.122 These factors are not much smaller than that obtained from a comparison of pyridine and quinoline reactivities.61,78,79... 

Again, Hess and Ljubitsch106 remarked that a combination of the phenomena of sulfonylation, chlorination, and quaternization failed to provide a coherent explanation for their observations on the prolonged treatment of cellulose with tosyl chloride in pyridine. Re-examination thereof, with special attention to the possible formation of anhydro rings (and, perhaps, of double bonds), is indicated. 

A special type of ABA block copolymer is formed when dendrimers are used as stoppers on rotaxanes. Rotaxanes are linear polymers onto which one or several large macrocycles are threaded. In order to prevent unthreading, sufficiently bulky groups must be attached to the two ends of the rotaxane. The [G-3] po-ly(benzyl ether) dendrimer proved to be highly suited for trapping [128] (see Scheme 16). The linear polymer is made of stiff bipyridinium groups that spontaneously assemble with diparaphenylene-34-crown-10 to form the rotaxane. The dendrimers are attached via quaternation of pyridine with benzyl bromide... 

A special type of ammonio group is represented by 4-( 1 -pyridinium)-pyridine and other azinium analogs.Such products often result from self-quaternization of highly reactive derivatives. A -(4-Pyridyl)-and A -(3-nitro-4-pyridyl)-pyridinium chloride hydrochlorides ... 

Many heterocyclic annulated isothiazolium salts are prepared by intramolecular quaternization of special 3-substituted salts. 

Special ionic liquids. A review of chiral ionic liquids is available/ A series of Lewis basic ionic liquids are prepared from DABCO by quaternization with RCl followed by anion exchange (to BF4, PFg)/... 

Deoxygenations, quaternizations, stable radical formations, and certain rare reaction types are included as the last few methods in the yearbook. The reaction symbols for these incorporates the special symbols El (electron pair), Het (heteropolar bond). Rad (radical), Res (resolutions), and Oth (other reaction types), e.g. 

In so far as microdomains in water are concerned, partially quaternized polytertiary amines with pendant tertiary amine groups possess a property of special interest. The deprotonated microdomains can be readily destabilized by adding strong acids, which cause protonation of tertiary amine residues and thus solubilize the polymer chains conventionally. The destabilization occurs at a constant pH through cooperative chemical and conformational transitions of the all-or-none type for a large range of the degree of protonation.2... 

In this contribution we first describe previous work dealing with the X-dependency of the physico-chemical properties of Q-P(TDAE)X compounds. Special emphasis will be given to the acid-base reaction-dependency of the dispersed microphase formed by the compounds with low X values. In a second part, we report recent work undertaken to evaluate the influence of the polymer backbone on acid-base reactions of partially quaternized polytertiary amines. Comparison will be made between a monomolecular globule-forming Q-P(TDAE)X and partially quaternized poly[(N-sec-butyl N-methyl aminomethyDethylene] Q-P(BM-AE)X, a compound with the same degree of methylation but with a backbone of the poly(olefin) type. 

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