title: H12461. Fluorine as a Regiocontrol Element in the Ring Openings of Bicyclic Aziridiniums.
abstract: The origin of the variation in the regioselectivity of the nucleophilic ring-opening of a series of bicyclic aziridinium ions derived fromN-alkylprolinols was investigated by quantum chemical computations (M06-2X/6-31+G(d,p)-SMD). These aziridiniums differ only in the degree and the stereochemistry of fluoro substitution at C(4). With the azide ion as nucleophile, the ratio of the piperidine to the pyrrolidine product was computed. An electrostaticgaucheeffect influences the conformation of the adjoining five-membered ring in the fluorinated bicyclic aziridinium. This controls the regioselectivity of the aziridinium ring-opening.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, USA, phone: +1-310-206-0515; fax: +1-310-206-1843;
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Lam
authors.forename: Kendall N
authors.initials: KN
authors.lastname: Houk
authors.forename: Janine
authors.initials: J
authors.lastname: Cossy
authors.forename: Domingo Gomez
authors.initials: DG
authors.lastname: Prado
authors.forename: Anne
authors.initials: A
authors.lastname: Cochi
keywords: aziridinium; computational chemistry; fluorine; gauche effect; nitrogen heterocycles