title: A 1,1-Carboboration Route to Bora-Nazarov Systems.
abstract: Hydroboration of the conjugated enynes 1 a and 1 b with Piers' borane [HB(C6F5)2] gave the respective dienylboranes trans-2 c and trans-2 d. Their photolysis resulted in the formation of the dihydroborole products 3 c and 3 d. Both were converted to their pyridine adducts 5 c and 5 d, respectively. Compounds 3 c and 5 c,d were characterized by X-ray diffraction. The reaction of the bis(enynyl)boranes 6 a and 6 b with B(C6F5)3 resulted in the formation of the dihydroboroles 7 a and 7 b, respectively. This reaction is thought to proceed by 1,1-carboboration of one of the enynyl substituents at boron to generate the dienylborane intermediates 8 a/8 b, followed by thermally induced bora-Nazarov ring-closure and subsequent stabilizing 1,2-pentafluorophenyl group migration from boron to carbon. Compound 7 a was characterized by X-ray diffraction and solid-state (11)B NMR spectroscopy.
authors.affiliation: Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149, Münster, Germany.
authors.forename: Fang
authors.initials: F
authors.lastname: Ge
authors.affiliation: Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149, Münster, Germany.
authors.forename: Fatma
authors.initials: F
authors.lastname: Türkyilmaz
authors.affiliation: Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149, Münster, Germany.
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.affiliation: Institut für Physikalische Chemie, Universität Münster, Corrensstraße 30, 48149, Münster, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Siedow
authors.affiliation: Institut für Physikalische Chemie, Universität Münster, Corrensstraße 30, 48149, Münster, Germany.
authors.forename: Hellmut
authors.initials: H
authors.lastname: Eckert
authors.affiliation: Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149, Münster, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Kehr
authors.affiliation: Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149, Münster, Germany. erker@uni-muenster.de.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Erker
keywords: alkenylboranes; boron; carboboration; heterocycles; ring closure