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.

SUBMITTER: Rana A 

PROVIDER: S-EPMC4734315 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature