A. 3D and 2D structure of each transition states for the acyclic reaction with their respective geometries and interaction (show in red in 2D). B. DFT optimized reaction mechanism with energies shown with respect to the reactants. All calculations were performed using a polarized continuum model for DCM solvation at -10°C. The largest energy barrier of 16.3 kcal/mol is between the acyclic sulfonylimine/PINC interaction complex and the first transition state (TS-1). The reaction is predicted to be highly exergonic with ΔG= -50.7 kcal/mol. PINC = N-isocyano triphenylphosphorane, Ph3P=O is triphenylphosphine oxide, TS = Transition State. Color code: grey, carbon; red, oxygen; blue, nitrogen; orange, phosphorous; yellow, sulphur; white, hydrogen. Full coordinates and animations can be found at . 3D and 2D structure of each transition states for the acyclic reaction with their respective geometries and interaction (show in red in 2D). These geometries are similar to ones obtained for the acyclic reaction. B. DFT optimized reaction mechanism with energies shown with respect to the reactants. All calculations were performed using a polarized continuum model for DCM solvation at -10°C. The rate limiting step has a barrier energy of 12.6 kcal/mol between the cyclic sulfonylimine/PINC interaction complex and the first transition state (TS-1). The reaction is predicted to be highly exergonic with ΔG= -49.4 kcal/mol. PINC = N-isocyano triphenylphosphorane, Ph3P=O is triphenylphosphine oxide, TS = Transition State. Color code: grey, carbon; red, oxygen; blue, nitrogen; orange, phosphorous; yellow, sulphur; white, hydrogen. Full coordinates and animations can be found at .