Abstract
Preparations of pyridine N-oxide (7a) and N-aminopyridinium chloride (10a) by ring opening of a quaternary pyridinium salt and successive recyclization were investigated, and the following methods established. Treatment of N-(2, 4-dinitrophenyl) pyridinium chloride (5a) with hydroxylamine, followed by refluxing the resulted 5-(2, 4-dinitroanilino)-2, 4-pentadienal oxime (6a) in dioxane-water (4 : 1) gave pyridine N-oxide (7a) in 87% yield from pyridine. Refluxing a mixture of N-(2, 4-dinitrophenyl) pyridinium chloride (5a) and hydrazine hydrate in dioxane-water (4 : 1) after being kept overnight at room temperature, gave N-aminopyridinium chloride (10a) in 50% yield from pyridine. The methods were proved to be applicable to conversions of β-, γ-picoline and 3, 5-lutidine into the corresponding N-oxides and N-amino derivatives.
