The regioselectivity in the intramolecular Diels Alder reaction (IMDA) of the molecule triene-amide for the synthesis in the hexahydroindole product, is done the object of our present work, two product regioisomers are feasible, the analysis of PES (potential energy surface) shows that the fused isomer is the main product and that bridged isomer is the minority product, this preference is also confirmed by the maximum hardness global (MHP), in this study we used the density functional theory (DFT) at the hybrid B3LYP and basis set level 6-31G (d, p), the geometries are optimized for reagents, thus the transition states and for products, the calculation of the bond order (BO) using natural population analysis (NBO) explains that all the transition states are asynchronous, and the analysis by IRC (intrinsic reaction coordinate) of the majority compound shows that the reaction IMDA is concerted.  The effect of the solvent toluene is taken into account by using the polarizable contium model (PCM).