Reaction mechanism among indoline-2,3-dione, pyrrolidine-2-carboxylic acid and (Z)-2-(1-(2-hydroxynaphthalen-1-yl)ethylidene)hydroxy-carboxamide to form 1'-((((aminooxy) carbonyl)amino)methyl)-2'-(1-hydroxynaphthalen-2-yl)-2'-methyl-1',2',5',6',7',7a'-hexahydrospiro[indoline-3,3'-pyrrolo[1,2-a]imidazole-2-one was investigated using density functional theory (DFT) at B3LYP level of theory. The three-step reaction occurred via five stationary points, including two van der Waals complexes (1 and 2), two intermediates and one transition state. The entropy change across the various steps indicated an appreciable interaction or overlap within the reacting molecules. This was also evident in variations in the geometries of the optimized species as the reaction progressed from the intermediates through the transition state to the final product. The steps leading to the formation of van der Waals complexes (1 and 2) were thermodynamically feasible in contrast to the bimolecular transition step. From the equilibrium constant value, the transition step was found to be the rate-determining step. The study is able to provide information on the energetics of the individual step of the reaction and the overall process in addition to change in geometries as the initial reacting molecules transformed through the saddle points to the final product.