Fig. 2. The optimized structures for TS modes of phosphoramide 3a-catalyzed α-azido indanone 1a and nitroolefin 2d. The relative Gibbs free energies are in kcal mol⁻¹, which were calculated at the IEFPCM-M06-2X-D3/6-311++G(d,p)//IEFPCM-M06-2X/6-31G(d,p) level. The bond distances are given in Å.