Displacement quaternary amine

For example, Mannich reaction of N-methylpyrrole affords the corresponding dimethylaminomethyl derivative (2) and treatment with methyl iodide affords the quaternary salt (3). Displacement of the quaternary amine by means of cyanide leads to the substituted... 

There are three common approaches to the displacement of amine substituents from purines. First, diazotization and dediazoniation have been used to replace amine substituents, primarily with hydrogen or hydroxyl, carboxyl, and halide functionalities. Second, the S Ar reactions of quaternary ammonium substituents have provided useful synthetic adjuncts to the displacement reactions of halopurines. Finally, of increasing importance has been the conversion of aminopurines (or oxopurines) to N-linked 1,2,4-triazoles (and other azoles), which function as pseudohalogens and can be displaced by nucleophiles or take part in transition metal-catalyzed reactions. 

The radiolabel was introduced by displacement of a quaternary amine with potassium 14C-cyanide to give a nitrile. The nitrile was readily converted to indole-3-acetic acid by hydrolysis with 20% aqueous potassium hydroxide. Reduction of the indole-3-acetic acid derivative with lithium aluminum hydride in tetrahydrofuran gave a typtophol with 95% yield. 

To establish a real displacement train it is necessary to feed the column with a compound with an even higher affinity to the stationary phase after the sample mixture has been injected. This compound is the so-called displacer. The optimum displacer has to be found empirically. For silica as the stationary phase, quaternary amines are often suitable (if the sample components are not acids) for reversed phases, alcohols can be used. It is necessary to regenerate the column after each separation. 

The mechanism of action of the nitrogen mustards (14) is depicted in Figure 42.1. In step 1, the lone pair of electrons on the un-ionized amino group conducts an intramolecular nucleophilic attack at the (3-carbon of the mustard, displacing chloride ion and forming the highly electrophilic aziridinium ion intermediate, a quaternary amine salt. The carbon atoms of this strained cyclic structure are highly electrophilic... 

Surfactant cations are difficult to displace from the clay mineral surface. Quaternary alkylammonium ions are easier to exchange than primary alkylammonium ions. Primary alkylammonium ions are removed by hydrolysis into the amine in alkaline medium [47]. The mutual exchange of surfactants in non-aqueous dispersions was studied by Me Atee [48, 49], Solvent was a mixture of isooctane and isopropyl alcohol. The alcohol served two functions as a solvent for the surfactant chloride salts and the dispersing agent for the clay mineral surfactant particles. An effective agent to displace quaternary alkylammonium ions (dodecyl trimethylammonium ions) is paraquat [50],... 

Allylic amine is a less reactive leaving group[7], but the allylic ammonium salts 214 (quaternary ammonium salts) can be used for allylalion(l30,131]. Allylic sulfonium salts are also used for the allylation[130]. The allylic nitrile in the cyclic aminonitrile 215 can be displaced probably via x-allylic complex formation. The possibility of the formation of the dihydropyridinium salts 216 and subsequent conjugate addition are less likelyfl 32],... 

Chemical Properties. Reactions of quaternaries can be categorized iato three types (169) Hoffman eliminations, displacements, and rearrangements. Thermal decomposition of a quaternary ammonium hydroxide to an alkene, tertiary amine, and water is known as the Hoffman elimination (eq. la) (170). This reaction has not been used extensively to prepare olefins. Some cycHc olefins, however, are best prepared this way (171). Exhaustive methylation, followed by elimination, is known as the Hoffman degradation and is important ia the stmctural determination of unknown amines, especially for alkaloids (qv) (172). 

Displacement of a tertiary amine from a quaternary (eq. lb) iavolves the attack of a nucleophile on the a-carbon of a quaternary and usually competes with the Hoffman elimination (173). The counterion greatiy iafluences the course of this reaction. For example, the reaction of propyltrimethylammonium ion with hydroxide ion yields 19% methanol and 81% propylene, whereas the reaction with phenoxide ion yields 65% methoxybenzene and 15% propylene (174). 

Methyl bromide slowly hydrolyzes in water, forming methanol and hydrobromic acid. The bromine atom of methyl bromide is an excellent leaving group in nucleophilic substitution reactions and is displaced by a variety of nucleophiles. Thus methyl bromide is useful in a variety of methylation reactions, such as the syntheses of ethers, sulfides, esters, and amines. Tertiary amines are methylated by methyl bromide to form quaternary ammonium bromides, some of which are active as microbicides. 

Aminodebromination of 4-bromo-l//-3-benzazepin-2-amine (25) with triethylamine occurs readily and results in formation of the quaternary salt 26 (see also Section 3.2.1.5.6.), whereas attempts to effect nucleophilic substitution of bromide with primary or secondary amines gives only tarry mixtures.41 The bromo group is also resistant to displacement by azide and benz-cncthiolate but undergoes substitution with thiocyanate ion in hot dimethylformamide to give the 4-thiocyanato derivative 27 rather than the thiourea by addition at the amine function. 

The Delepine reaction Involves nucleophilic displacement of active halides by hexamethylenetetramine, followed by hydrolysis of Intermediate quaternary ammonium salt to release the amine. 

Secondary amines, such as pyrrolidine, must be alkylated with care too polar a solvent leads to participation of a second nearby polymer-bound alkylant in the formation of a quaternary ammonium salt, along with the desired immobilized trialkyl amine. The exception, as seen above, is diisopropylamine, which refuses to displace tosylate even in the refluxing pure amine, or in hot dimethyl-formamide or other polar solvent, while metal diisopropylamide is notorious as a powerful non-nucleophilic base. However, carboxamide is not difficult to form from (carboxymethyl)polystyrene, again using toluenesulfonyl chloride as condensing agent this can then be reduced to (diisopropyl-ethylaminoethyl)polystyrene, which is of interest as a polymer-bound non-nucleophilic base. ... 

---