Fig. 7: Computational investigation of the mechanism to explain the reaction performance.

a, The desired and undesired pathways of the pyridinium ylide-mediated cycloaddition. The possible undesired pathways were suggested by a systematic search using the AFIR method at the ωB97X-D/LanL2DZ/CPCM(THF) level of theory (see the Supplementary Information for details). The pathway with the lowest energy barrier among the pathways for the first step from two molecules of I, which was obtained by optimizing the transition-state geometries at the ωB97X-D/Def2-SVP/CPCM(THF) level of theory, is shown. b, Comparison of the energy barriers for each coupling partner with the experimental results. The energy barriers for the cycloadditions were evaluated at the same level of theory. Reaction conditions: 2a (0.30 mmol, 1 equiv.), coupling partner (0.60 mmol, 2 equiv., or under a 1 atm ethylene atmosphere with a balloon), Me3SiCF2Br (0.33 mmol, 1.1 equiv.), Ph3SiF2·NBu4 (0.33 mmol, 1.1 equiv.) and THF (3 ml) at 0 °C for 2 h. Yields were determined using 19F NMR spectroscopic analysis with benzotrifluoride as the internal standard.