Abstract
Flash vacuum pyrolysis is an interesting methodology for studying reaction mechanisms as well as synthesis. Its characteristics of submitting the molecule to high temperature (350 - 900ºC) in a vacuum system (∼ 10-2 Torr) for a short time (∼ 10-2s) makes possible to isolate kinetically controlled products and, in some cases, to avoid consecutive reactions. Studies of reaction mechanisms may include kinetic and non-kinetic methods, and of course, the knowledge of reaction mechanisms and the influence of substituents in it, makes possible the synthetic application of these reactions. In this review reactions of different nitrogen heterocycles will be divided by type of reaction, such as isomerizations, radical reactions, nitrogen extrusion, eliminations, and reactions of the side chain. Special attention will be dedicated to kinetic measurements because it is not a common way to study flash vacuum pyrolysis reactions but they give important information about reaction mechanisms. An improvement of flash vacuum pyrolysis reactions with the use of solid catalysts will also be discussed. These catalysts have two effects, in some cases they lower the reaction temperature and in some others there is a change of the reaction with formation of different products. These results extend the possibilities of flash vacuum pyrolysis of a single substrate.
Keywords: flash vacuum pyrolysis, pyrazoles, nitrogen heterocycles, isomerizations, radical reactions, nitrogen extrusion
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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