DFT study on reaction mechanisms of propylamine and dimethyl acetylenedicarboxylate with 1,3-dimethylalloxan

► A proton migration mechanism and a new mechanism were studied for the title reaction with DFT. ► The new mechanism follows a simple route that avoids complicated steps in proton transfer. ► The new mechanism is the most energetically favorable pathway. ► In agreement with experiment, the reaction can occur easily at room temperature.