(intermediate-1). In the next step, the complex is photoactivated to form the imine free-radical intermediate To explore the feasibility of the reaction pathways, DFT calculations were conducted using the Gaussian 09 package. The DFT method of the B3LYP functional was used with a 6-31+G(d,p) basis set to optimise the geometry of molecules in acetone. Frequency analyses were performed to verify the absence of imaginary frequencies. The solvent effect was taken into consideration with a SMD continuum solvation model . The free-energy profiles of these pathways were calculated using the B3LYP method in acetone. As shown in Fig. suggest that in the presence of LiOH, the corresponding mechanism for the primary and secondary reactions followed pathways e and d, respectively. These results are also consistent with the experimental data, suggesting that 5a and 3a are the major and minor products, respectively, for the current reaction sequence. These observations further provide crucial insights into the possible mechanism of the cyclisation and rearrangement reactions, explored in this study.