Structure quaternary salts

Many monomeric heterocyclic anhydrobases can be isolated now using specific methods (44), but application of these methods to thiazole ring did not succeed however, appropriate conditions lead to the separation of a dimer, the structure of which has been established by its NMR Spectra and chemical reactivity (26). The most probable mechanism of its formation appears identical with the one previously described in the benzothiazolium series (24). A second molecule of quaternary salt A3... 

It has long been known that quaternary ammonium salts can exert a curare-like action, and in recent years much attention has been given to the synthesis and pharmacological testing of such products work on this subject up to 1936 has been reviewed by Ing, and more recently a theoretical discussion of the relationship between structure and action in drugs of this type has been provided by Holmes, Jenden and Taylor.Chase, Lehmann and Yonkmann have compared the action of quaternary salts of quinine with that of -erythroidine hydrochloride and of dihydro- -erythroidine hydrobromide. Quinine ethochloride shows marked curariform action of short duration. ... 

In the case of the bases derived from quaternary heterocyclic ammonium salts, the carbinolamines (5) can react as cyclic aldehyde-ammonias with many reagents with which the amino-aldehyde (7) could react. However, reactions of the carbinolamines which are not characteristic of amino-aldehydes are also known. Carbinolamines can easily be reconverted into the quaternary salts by the action of dilute acids, and they form alkyl ethers very easily with alcohols. If these last reactions do not occur, then this is convincing evidence for the base possessing the amino-aldehyde structure. However, if these reactions do occur this does not provide unambiguous confirmation of the carbinolamine structure. They are also given by the bi-molecular ethers (8), and, in the case of a tautomeric equilibrium... 

The reactivity of the methyl group in 4-methylcinnoline ethiodide indicates that the structure of this compound is 5, and this evidence has also been interpreted to mean that N-1 is the basic group in cinnolines. However, evidence of this type is only indicative since the formation of quaternary salts is subject to kinetic control, whereas protonation yields predominantly the thermodynamically more stable cation. The quinazoline cation has been shown to exist in the hydrated, resonance-stabilized form 6 7 by ultraviolet spectro-... 

Many of the quaternary salts discussed in this section and in Section V may be represented by two or more canonical forms. Such resonance, where it occurs, is obvious and therefore only one of the structures is given. 

Cyanine dyes have been prepared from the salts obtained by the quatemization of 4,6-dimethyl-2-phenylpyrimidine and 2-alkyl- or 2-aryl-4,6-dimethylthiopyrimidines, but there can be no ambiguity in the structure of these quaternary salts. 

The quaternization of pyrazine compounds has not been extensively studied, and, therefore, a detailed discussion of the effect of substituents is not possible. Recently Cheeseman has shown, from spectroscopic evidence, that 2-amino- and 2-diethylamino-pyrazine (50, Y = NH2 and NEt2) quatemize at N-4, although protonation occurs at position-1. Other substituted pyrazines from which quaternary salts of structure 51 are formed include 2-chloro- and 2-... 

The corresponding [5,4-6]-compound (107) was prepared similarly and treated with methyl iodide to give a quaternary salt which was shown to have structure 108, because mild alkaline hydrolysis gave 3-acetamido-l-methyl-2-pyridone. Again, quaternization took place on the pyridine-nitrogen, which is different from the behavior of the corresponding 1,4-diazaindene mentioned above. 

The quaternary salt from 2-methylthiothiazolo[4,5-c]pyridine (111 Y = SMe) has been described but no structure has been advanced. Again the Russian workers report that a bis-etho-toluene- -sulfonate... 

Quaternary salts have been prepared from a number of these bases. 7-(Dialkylaminoalkyl)amino-l,2,3a,4-tetraazaindenes (132) were prepared and converted into mono-quaternary salts, but no structures were assigned to the salts and the quaternary center may well be in the side-chain. When this ring system carries 3-methyl and 5-alkyl or... 

It is only recently that the first pteridine quaternary salt was prepared. Brown and Jacobson treated 4-dimethylaminopteridine (156) and its 6,7-dimethyl derivative with methyl iodide in boiling methanol and obtained the corresponding salts (cf, 157). The structure of these... 

The early stages of the reaction of the quaternary salt can be regarded as proceeding in a manner exactly analogous to that by which the isoxazoles themselves are degraded, the j8-oxoketene imine structure (148) being one mesomeric form of a compound which could alternatively be formulated as a nitrilium betaine. However, by contrast with the products from the isoxazoles (i.e., enolates of /3-keto-nitriles), this is electrically neutral and susceptible to further nucleophilic attack. 

The structures of these ylide polymers were determined and confirmed by IR and NMR spectra. These were the first stable sulfonium ylide polymers reported in the literature. They are very important for such industrial uses as ion-exchange resins, polymer supports, peptide synthesis, polymeric reagent, and polyelectrolytes. Also in 1977, Hass and Moreau [60] found that when poly(4-vinylpyridine) was quaternized with bromomalonamide, two polymeric quaternary salts resulted. These polyelectrolyte products were subjected to thermal decyana-tion at 7200°C to give isocyanic acid or its isomer, cyanic acid. The addition of base to the solution of polyelectro-lyte in water gave a yellow polymeric ylide. 

Polk et al. reported27 that PET fibers could be hydrolyzed with 5% aqueous sodium hydroxide at 80°C in the presence of trioctylmethylammonium bromide in 60 min to obtain terephthalic acid in 93% yield. The results of catalytic depolymerization of PET without agitation are listed in Table 10.1. The results of catalytic depolymerization of PET with agitation are listed in Table 10.2. As expected, agitation shortened the time required for 100% conversion. Results (Table 10.1) for the quaternary salts with a halide counterion were promising. Phenyltrimethylammonium chloride (PTMAC) was chosen to ascertain whether steric effects would hinder catalytic activity. Bulky alkyl groups of the quaternary ammonium compounds were expected to hinder close approach of the catalyst to the somewhat hidden carbonyl groups of the fiber structure. The results indicate that steric hindrance is not a problem for PET hydrolysis under this set of conditions since the depolymerization results were substantially lower for PTMAC than for die more sterically hindered quaternary salts. 

Among the recently (as of 2003) described reactions of such quaternary salts, reduction to dihydroquinoxalines has been exemplified toward the end of Section 2.2.4 treatment of the diquaternary compound, 1,4,6,7-tetramethylquinox-alinediium bis(tetrafluoroborate) (215), with sodium iodide gave a well-characterized product that appears in X-ray studies to have the cation radical structure (216) ""° and a fundamental spectrophotometric study on the addition of hydroxyl and methoxyl ions to the 1-methylquinoxalinium cation has been reported. ... 

In our previous work [8], we rqjorted the synthesis of (2-oxo-l,3-dioxolan-4-yl)methacrylate (DOMA) finrn carbon dioxide and glycidyl methacrylate (GMA) using quaternary salt catalysts. In the present work, we studied the catalytic pra rmance of alkyhnethyl imidazolium salt ionic liquid in the synthesis of polycarbonate from the copolyraerization of CO2 with GMA. The influences of copolymerization variable like catalyst structure and reaction tenperature on the conversion of GMA and the yield of the polycarbonate have been discussed. 

The most recent extension of the 4 + 2 cycloaddition to aromatic quaternary salts has been carried out with isoquinolinium salts (42), in effect, dispensing with ring A of the acridizinium ion. Although there was an earlier claim that the addition of an ynamine to 2-methyl-isoquinolinium iodide led to a 2 1 adduct, the assigned structure... 

The structures of other charged pyridines such as quaternary salts (7), zwitterions (8) arising from /3-hydroxypyridines (9), another aspect of tautomerism, and ylides (10) will also be considered. 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

Quaternary salts having structure 51 have been isolated R, and R2 are amino, alkoxy, and thioalkoxy substituents. Except in the case of 2-amino products, dealkylation to give a 2-pyrimidone takes place readily under alkaline conditions.158... 

A7-Acyl derivatives of heterocycles can often be quatemized by hard alkylating agents, such as trialkyloxonium fluoroborates406 or methyl fluorosulfonate.364 The quaternary salt is not usually isolated, but N-alkylated derivatives are obtained whose structures are generally different from those obtained by alkylation of anions (Sections IV,C,2). This method, due to Olofson and Kendall,406 has been used with success in azapentalenes [Eqs. (34) and (35)1, where the products 384 and 385 are different from those obtained by alkylation of the anions 361 and 364, respectively (Scheme 16). 

Pyrazolo[4,3-c]pyridines gave 5-methiodides in excellent yield.144 154 A methiodide of pyrazolo[l,5-a]pyridine 199b (R1 = H) was also prepared but its structure was not assigned161 the parent compound 5 quaternized in the 1-position.209 The saturated amide, however, formed a 7a-quaternary salt (263) with benzyl chloride, which was converted to the 1-benzyl derivative via the internal salt 264.209... 

Acyl and sulfonyl halides and anhydrides react instantaneously with pyridine to form quaternary salts which are excellent acylating and sulfonylating agents. The familiar use of pyridine as a solvent in such reactions reflects this. While usually used in situ, stable A-acylpyridinium and N-acylisoquinolinium salts, e.g. (63), have been isolated and their structures confirmed by single crystal... 

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