title: A General Route to β-Substituted Pyrroles by Transition-Metal Catalysis.
abstract: An atom-efficient route to pyrroles substituted in the β-position has been achieved in four high yielding steps by a combination of Pd, Ru, and Fe catalysis with only water and ethene as side-products. The reaction is general and gives pyrroles substituted in the β-position with linear and branched alkyl, benzyl, or aryl groups in overall good yields. The synthetic route includes a Pd-catalyzed monoallylation step of amines with substituted allylic alcohols that proceeds to yield the monoallylated products in moderate to excellent yields. In a second step, unsymmetrical diallylated aromatic amines are generated from the reaction of a second allylic alcohol with high selectivity in moderate to good yields by control of the reaction temperature. Ru-catalyzed ring-closing metathesis performed on the diallylated aromatic amines yields the pyrrolines substituted in the β-position in excellent yields. By addition of ferric chloride to the reaction mixture, a selective aromatization to yield the corresponding pyrroles substituted in the β-position was achieved. A reaction mechanism involving a palladium hydride, generated from insertion of palladium to O-H of an allyl alcohol, that is responsible for the C-O bond cleavage to generate the π-allyl intermediate is proposed.
authors.affiliation: Department of Chemistry, BMC, Uppsala University , Box 576, 751 23, Uppsala, Sweden.|Department of Organic Chemistry, Stockholm University , 106 91, Stockholm, Sweden.
authors.forename: Anon
authors.initials: A
authors.lastname: Bunrit
authors.affiliation: Department of Chemistry, BMC, Uppsala University , Box 576, 751 23, Uppsala, Sweden.
authors.forename: Supaporn
authors.initials: S
authors.lastname: Sawadjoon
authors.affiliation: Department of Chemistry, BMC, Uppsala University , Box 576, 751 23, Uppsala, Sweden.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Tšupova
authors.affiliation: Department of Chemistry, BMC, Uppsala University , Box 576, 751 23, Uppsala, Sweden.
authors.forename: Per J R
authors.initials: PJ
authors.lastname: Sjöberg
authors.affiliation: Department of Chemistry, BMC, Uppsala University , Box 576, 751 23, Uppsala, Sweden.|Department of Organic Chemistry, Stockholm University , 106 91, Stockholm, Sweden.
authors.forename: Joseph S M
authors.initials: JS
authors.lastname: Samec