Figure 1.
Plausible reaction pathways explored in this study. (A) The concerted mechanism, in which the reaction passes through a phosphorane-like TS, which is depicted as the middle structure. The minimum energy pathway obtained in our previous study19 corresponds to this pathway. (B) A sequential pathway that passes through a bridging O5′ proton-transferred intermediate, which is depicted as the middle structure. (C) A sequential pathway that passes through a nonprotonated phosphorane intermediate, which is depicted as the middle structure. Note that all of the pathways are reversible but are shown only in one direction for clarity.