The pyrolysis and oxidative decomposition courses of a novel class of trifluoromethylated fused triazinones by using a Simultaneous thermal analysis (STA) coupled online with the Fourier transform infrared spectroscopy (FTIR) and the Quadrupole mass spectrometry (QMS) were determined. It was found that the pyrolysis and oxidation processes of these compounds run through simultaneous, radical processes in one, main stage in both: helium and air atmospheres. The FTIR and QMS analyses allowed confirming the simultaneous cleavage of Csingle bondCF3, Csingle bondN, Nsingle bondN, and Csingle bondCl bonds, formation of radical intermediates, reactions of radical intermediates with each other in a gaseous phase leading to the formation of final volatile products such as RNCO, CF3CN, CF3H, HCOCOH, alkenes, aromatic amine derivatives, CO2 and H2O in inert conditions as well as RNCO, CF3CN, CF3H, HCOCOH, alkenes, aromatic amine derivatives, CO2, CO and H2O in oxidative conditions. Moreover, the favourable thermal properties and high purity were highlighted in evaluating the suitability of trifluoromethylated compounds as potential candidates for pharmaceutical applications.