On the question of the zwitterionic intermediate in the (3+2) cycloaddition between 2-diphenylphosphinoyl-2-methyl-3,4-dihydro-2H-pyrrole N-oxide and di-t-butyl selenoketone: DFT mechanistic study

This work verified the hypothesis of a two-step, zwitterionic mechanism for the (3+2) cycloaddition reaction between 2‑diphenylphosphinoyl-2-methyl‑3,4‑dihydro-2H-pyrrole N‑oxide and di-t-butyl selenoketone. It turned out that the two-step mechanism of this transformation is possible, but via a less favored reaction pathway. Furthermore, the zwitterionic nature of the identified intermediate appears disputable. In addition to this considerations, the regio- and stereoselectivity of the process was also identified. It was found that the kinetically most favored reaction pathway yields a product that allows for subsequent transformation to the experimentally observed molecules.