title: Mechanistic studies on the Pd-catalyzed direct C-H arylation of 2-substituted thiophene derivatives with arylpalladium bipyridyl complexes.
abstract: Direct C-H phenylation of 2-ethylthiophene and 2-chlorothiophene with PhPdI(bipy) complex to form either the corresponding 4-phenyl or 5-phenylthiophene derivative is studied under stoichiometric conditions using various Lewis acids as additives. It is shown that reactions occur via the corresponding cationic Pd complex (PhPdbipy(+)) and that the counteranion determines the regioselectivity. High-level DFT calculations reveal that C-C bond formation occurs via a carbopalladation pathway and not via electrophilic palladation. These calculations give some indications regarding the regioselectivity of the thiophene arylation.
authors.affiliation: Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149 Münster, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Steinmetz
authors.forename: Kirika
authors.initials: K
authors.lastname: Ueda
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.forename: Junichiro
authors.initials: J
authors.lastname: Yamaguchi
authors.forename: Sylvia
authors.initials: S
authors.lastname: Kirchberg
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Itami
authors.forename: Armido
authors.initials: A
authors.lastname: Studer