Pyridine-1-oxonium chloride, reaction

Pyridine 23 (two equivalents) reacts with chlorosulfonic acid in an inert organic solvent, e.g. carbon tetrachloride, to yield equimolar quantities of the pyridine-sulfur trioxide complex and pyridinium chloride this behaviour is typical of the reaction of a tertiary amine with the reagent (see Chapter 4, p 101). The potentiometric curve for the neutralization of chlorosulfonic acid by pyridine in nitromethane has been determined and showed two steps. Pyridine 1-oxonium chloride similarly yields the pyridine-sulfur trioxide adduct on treatment with chlorosulfonic acid. ... 

Reaction of pyridine-N-oxides with triethyloxonium salt in methylene chloride or chloroform gives directly AT-alkoxy pyridinium salts with high yield. Quinolinium salts can also be prepared from the corresponding N-oxides [46], The synthetic procedure does not require the anion exchange reaction since triethyl oxonium salt possesses a non-nucleophilic counter anion, i.e. PFg ... 

N-Alkoxy Pyridinium Salts /V-Alkoxy Pyridinium salts are obtained with relatively high yields by a reaction of pyridine /V-oxides with a triethyloxonium salt in methylene chloride or chloroform [13]. Quinolinium salts can also be prepared from the corresponding /V-oxides [40], In both cases, an anion exchange is not necessary since the triethyl oxonium salt is available with nonnucleophilic counter anions. The most frequently used photoinitiators of this type are shown in Chart 11.8. The spectral response of these salts is in 260-310 nm range [13],... 

It is believed that methyl aromatic ether is protonated from the thermally stable pyridine hydrochloride to form an oxonium ion, which undergoes nucleophilic substitution with chloride to evolve methyl chloride and yield phenol derivatives, as exemplified here by the reaction of anisole. 

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