title: The importance of the ene reaction for the C(2)-C(6) cyclization of enyne-allenes.
abstract: The present study establishes the ene reaction as a competing reaction mechanism to the diradical mechanism for the thermal C(2)-C(6) cyclization of enyne-allenes which possess bulky substituents at the alkyne terminus. Both reaction routes are found to possess nearly equal free energies of activation. As shown by our computations, primary H/D isotope effects could be used for a definite decision about the mechanism. Concerning the regioselectivity of the cyclization reactions of enyne-allenes our study resolves a long-standing deviation between theoretical results and experimental findings.
authors.affiliation: Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: P W
authors.initials: PW
authors.lastname: Musch
authors.forename: B
authors.initials: B
authors.lastname: Engels