title: Facile Route to Quadruply Annulated Borepins.
abstract: A two-step synthesis sequence furnishes quadruply annulated borepins in high yields. The first step involves a nucleophilic substitution reaction between aryl-BF3K salts (aryl = mesityl, phenyl) and lithiated bromonapthalene derivatives LiNaphBr,R(HNaphBr,R= 8-bromonaphthalene (a), 5-bromoacenaphthene (b), 5-bromoacenaphthylene (c)). In the second step, the resulting heteroleptic triarylboranes aryl-B(NaphBr,R)2(3a-c) are subjected to an intramolecular Ni-mediated Yamamoto reaction to close the seven-membered rings and create the borepins 4a-c. Only in the case of 3b is the Yamamoto reaction accompanied by a C-H activation reaction furnishing the 7-hydro-7-borabenzo[de]anthracene derivative 5. The product ratio 4b/5 can be influenced by control of the local Ni(0) concentration. The borepins 4a-c are benchtop stable and highly soluble even in hexane. Compounds 4a-c undergo reversible one-electron reduction; 4c is also able to accept a second electron in a reversible manner and already at moderate potential values (E1/2= -1.49 V and -1.84 V (vs FcH/FcH+)). 4a, 4b, and 5 show photoluminescence in the blue-green region of the spectrum, while 4c is nonfluorescent, which is likely attributable to an intramolecular charge-transfer transition.
authors.affiliation: Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt , Max-von-Laue-Strasse 7, D-60438 Frankfurt (Main), Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Schickedanz
authors.affiliation: Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt , Max-von-Laue-Strasse 7, D-60438 Frankfurt (Main), Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Radtke
authors.affiliation: Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt , Max-von-Laue-Strasse 7, D-60438 Frankfurt (Main), Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Bolte
authors.affiliation: Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt , Max-von-Laue-Strasse 7, D-60438 Frankfurt (Main), Germany.
authors.forename: Hans-Wolfram
authors.initials: HW
authors.lastname: Lerner
authors.affiliation: Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt , Max-von-Laue-Strasse 7, D-60438 Frankfurt (Main), Germany.
authors.forename: Matthias
authors.identifier: 0000-0001-5806-8276
authors.initials: M
authors.lastname: Wagner