Cyclic quaternary ammonium

Ring enlargement of cyclic quaternary ammonium salts (cyclic... 

The cathodic reduction of cyclic quaternary ammonium compounds can involve a cleavage at the N atom with ring opening as observed for andiriium salts (Scheme 164) [244]. 

Ring enlargement of cyclic quaternary ammonium salts (cyclic amines) 8-33 Ring expansion of N-acylaziridines (oxazoles)... 

In all cases initiation is fast and quantitative, and propagation seems to take place via cyclic quaternary ammonium ions... 

Cyclizations of alkenic amines and imines using organoiron complexes to generate bicyclic 3-lactams are discussed in Chapter 3.1 of this volume. Examples of heterocyclizations of alkenic NA/-dialkylamine and pyridine derivatives to form cyclic quaternary ammonium salts are cited in the Staninets review.Ic A cyclization of an enol thioether has been used to generate a thiazolidine intermediate used in cephalosporin synthesis (equation 131).262... 

The formation of covalent branching points is avoided in the cationic polymerization of -substituted aziridines. Chain transfer to polymer occurs, however, leading to formation of branched (or cyclic) quaternary ammonium ions, unreactive in further propagation [165). 

More complex equilibria (Fig. 76), also involving chemical modifications, are shown by the aminomethyl derivatives of a-arylidene-P-ketoesters (207), studied as anticancer drugs - these have been found to be in equilibrium with cyclic quaternary ammonium salts, which in turn are characterized by the presence of kcto-enol equilibrium. 

Dialkylaminoalkylphenothiazines may be prepared replacing the usual condensating agent, sodamide, by an excess of sodium hydroxide. In the case of alkyl or haloalkyl halides the V-substitution of phenothiazine in the presence of sodium hydroxide fails. The formation of intermediate cyclic quaternary ammonium salts (133) from the dialkylaminoalkyl halides was suggested to explain this effect. Quaternary ammonium salts appear to catalyze the condensation of alkyl halides with phenothiazine in the presence of NaOH. ... 

Iverson and Madsen [193] reported a synthetically interesting electroreductive ringopening reaction of cyclic quaternary ammonium salts. The stereochemistry of products is greatly affected by pH ... 

Zhou Z B, Matsumoto H, Tatsumi K. Cyclic quaternary ammonium ionic liquids with perfluoroalkyltritluoroborates Synthesis, characterization, and properties. Chem. Eur. J. 2006. 12, 2196-2212. 

Extensive studies by X-rays, IR-, and NMR-spectroscopy (65, 66, 68) on the stereoisomeric pairs of cyclic quaternary ammonium salts showed a preferable axial approach in the quaternization of the iV-alkyl cam-phidine, 2-methylpyrrolidine, and piperidine series while for tropanes the equatorial approach has been substantiated. The increase of a band takes place in the higher region (885-900 cm i) when the iV-methyl is equatorial while the same change occurs in the lower region (840-885 cm i) when iV-methyl is axial (65). The NMR-spectra of a series of iV-methyl and iV-alkyl nortropanium salts show the signal at 7.10 r for the equatorial position and at 6.97 t for the axial one (66). 

VIII. Ylids from Cyclic Quaternary Ammonium Salts. 349... 

Le M-L-P, Alloin F, Strobel P, Lepretre J-C, Cointeaux L, del Valle CP (2012) Electrolyte based on fluorinated cyclic quaternary ammonium ionic liquids. Imiics 18 817-827... 

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