GAS-PHASE SELECTIVE OXIDATION OF SOME PYRIDINE DERIVATIVES WITH A “GREEN OXIDIZER”—N₂O IN THE COHERENT SYNCHRONIZATION MODE

Introduction

One of the practical applications of the principle of coherently synchronized oxidation could be the transformation of natural compounds for preparative purposes, and possibly on a larger scale. However, in order to move on to more complex nitrogen-containing heterocyclic compounds, similar in chemical structure to natural ones, it is necessary to study the corresponding reactions involving their individual fragments.

Methods

Oxidation reactions of nitrogen-containing heterocyclic compounds in the presence of N₂O were carried out in the gas phase, without the use of catalysts, at atmospheric pressure. Quantitative and qualitative determination of the resulting reaction products was carried out using “Agilent Technologies 7820A” gas chromatography–mass spectroscopy.

Results

The dehydrogenation reaction of piperidine was studied. As a result of our research (T = 200–400°C), optimal conditions for the dehydrogenation of piperidine were identified, under which a yield of 2,3,4,5-tetrahydropyridine (19.4 wt%) was achieved with a selectivity of at least 98%.

The oxidation of pyridine with N₂O was carried out in a wide range of varying process parameters: feed rate of pyridine and N₂O (T = 550-610°C). Under optimal conditions, the following were obtained: 2,2-dipyridyl with a yield of 23.0 wt.%, and 2,3-dipyridyl with a yield of 18.0 wt.%, selectivity not lower than 95 wt.%.

For the first time, 2,2-ethylenedipyridine was obtained by the oxidation of 2-picoline with N₂O. It has been experimentally shown that the yield of 2,2-ethylenedipyridine and 2,2-methylenedipyridine is 30.3 wt.% and 1.5 wt.%, respectively, where the selectivity is not lower than 96 wt.%.