title: Solving the puzzling competition of the thermal C(2)-C(6) vs Myers-Saito cyclization of enyne-carbodiimides.
abstract: The mechanism of the thermal cyclization of enyne-carbodiimides 7a-c has been studied computationally by applying the DFT method. The results indicate that enyne-carbodiimides preferentially follow the C(2)-C(6) (Schmittel) cyclization pathway in a concerted fashion although the Myers-Saito diradical formation is kinetically preferred. The experimentally verified preference of the C(2)-C(6) over the Myers-Saito pathway is guided by the inability of the Myers-Saito diradical to kinetically compete in the rate-determining trapping reactions, either inter- or intramolecular, with the concerted C(2)-C(6) cyclization. As demonstrated with enyne-carbodiimide 11, the Myers-Saito channel can be made the preferred pathway if the trapping reaction by hydrogen transfer is no more rate determining.
authors.affiliation: Department of Chemistry and Biology, Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany.
authors.forename: Anup
authors.initials: A
authors.lastname: Rana
authors.affiliation: Department of Chemistry and Biology, Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany.
authors.forename: Mehmet Emin
authors.initials: ME
authors.lastname: Cinar
authors.affiliation: Department of Chemistry and Biology, Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Samanta
authors.affiliation: Department of Chemistry and Biology, Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schmittel
keywords: DFT computation; diradical; enyne-carbodiimides; hydrogen transfer; thermal cyclization