CONICET | Buscador de Institutos y Recursos Humanos

Gas-phase thermal reactions have proven to be interesting methodologies to study reaction mechanisms and for synthesis. Flash vacuum pyrolysis (FVP) is one of these reactions and consists in submitting a molecule to the application of high temperature (350-900ºC) during a short period of time (~10-2 s). This important feature allows getting kinetic as well as unstable products. FVP reactions are normally clean, without solvent, so they normally involve carbenes, nitrenes, radicals and concerted process. Thus, FVP can be used as a single step synthetic procedure as well as a complement of a multistep route. Applications of FVP as well as other gas phase thermal procedures to the study of different heterocycles (pyrazoles, thiadiazoles, selenazoles, triazines, azepines) have been explored. The most common reactions that afford heterocycles are cyclizations of unsaturated compounds, ring fragmentations including retro Diels-Alder reactions, isomerizations and extrusion of small neutral molecules (N2, SO2, CO2). An improvement of FVP reactions with the use of solid catalysts (zeolites, MCM-41, scheelites) was also studied. 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.In a recent approach to combine the features of the gas phase thermal reactions and the benefits of microwave irradiation, a new system denominated Microwave Flash Pyrolysis was developed. This alternative methodology was used to study the synthesis of seleno-compounds which are not conveniently prepared by conventional reactions.