Theoretical and experimental study on the reaction route for the FVP of 2-thioxohexahydroquinazolinones

► Thermal decomposition of cis/trans 2-thioxo-hexahydroquinazolinones. ► Conformational analysis confirming the decomposition mechanism. ► Hetero-ring opening from thiol tautomer (N(1)-in conformation) as main reaction. ► Results supported by MS and DFT calculations.