Scheme 1. reaction steps for the synthesis of MNTzA and BADCh by FOX-7
Computational details
All geometric optimizations are performed at the density functional theory (DFT) level by using hybrid B3LYP functionals [21-23] with the basis set def2-TZVP [24,25]. The properties of the optimized stationary points are characterized by the frequency calculations at the same theoretical level, with no imaginary frequency for all reactant, intermediate, and product configurations, and an imaginary frequency mode for all transition states (TSs). Thermal correction of the electron energy for the optimized geometry was estimated at an experimental temperature of 373 K and 1 atmosphere, based on frequency calculations. Water was used as the solvent, and PCM method [26] was used for SCRF calculation to simulate the solvent effect. The intrinsic reaction coordinates (IRC) [27] calculations from first-order saddle points were performed to locate the local minimum of the reaction path, which is represented by a solid line in the energy distribution. In order to obtain more accurate electron energies and reaction barrier heights, single-point calculations based on the optimized geometry is further performed by using the B3LYP functional with a larger basis set def2-QZVP [28]. Gaussian 16 program [29] is used for all DFT calculations.