title: Reaction Mechanism of Iodine-Catalyzed Michael Additions.
abstract: Molecular iodine, an easy to handle solid, has been successfully employed as a catalyst in different organic transformations for more than 100 years. Despite being active even in very small amounts, the origin of this remarkable catalytic effect is still unknown. Both a halogen bond mechanism as well as hidden Brønsted acid catalysis are frequently discussed as possible explanations. Our kinetic analyses reveal a reaction order of 1 in iodine, indicating that higher iodine species are not involved in the rate-limiting transition state. Our experimental investigations rule out hidden Brønsted acid catalysis by partial decomposition of I2to HI and suggest a halogen bond activation instead. Finally, molecular iodine turned out to be a similar if not superior catalyst for Michael additions compared with typical Lewis acids.
authors.affiliation: Universität zu Köln , Department für Chemie, Greinstraße 4, 50939 Köln, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: von der Heiden
authors.affiliation: Universität zu Köln , Department für Chemie, Greinstraße 4, 50939 Köln, Germany.
authors.forename: Seyma
authors.initials: S
authors.lastname: Bozkus
authors.affiliation: Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Klussmann
authors.affiliation: Universität zu Köln , Department für Chemie, Greinstraße 4, 50939 Köln, Germany.
authors.forename: Martin
authors.identifier: 0000-0003-0950-8858
authors.initials: M
authors.lastname: Breugst