Gas phase thermal reactions: recent applications.

ELIZABETH L. MOYANO

Potchestroom

Seminario; Presentación en el marco del convenio DST-MINCYT-(SA0904).; 2013

Center of Excellence for Pharmaceutical Sciences. North West University

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 (350-900 ºC) 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, and 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 nitrogen heterocycles have been explored. The most common reactions that afford heterocycles are cyclisations 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 different solid catalysts (zeolites, MCM-41, scheelites) was also studied. These catalysts have two effects, in some cases the reaction temperature is lowered 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.