title: Unusual pathway taken in the reaction of bis(alkynyl)diisopropylaminoboranes with B(C6F5)3.
abstract: The bis(alkynyl)diisopropyl-aminoboranes 7 were prepared by treatment of iPr2NBCl2 with two molar equivalents of 1-pentynyl lithium or lithium phenylacetylenide, respectively. Their reaction with one molar equivalent of B(C6F5)3 resulted in the formation of the 1,1-carboboration products 8 that were subsequently stabilized by adduct formation (9) with tert-butyl isocyanide. Thermolysis of 8a (R = nPr) proceeded with hydride transfer from a N-isopropyl substituent to the distal carbon atom of the remaining pentynyl unit at boron to give the zwitterionic five-membered heterocyclic product 10a in good yield. The analogous product 10b (R = Ph) was obtained upon photolysis of 8b. The compounds 7b, 9b, 10a, and 10b were characterized by X-ray crystal structure analysis.
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Fang
authors.initials: F
authors.lastname: Ge
authors.forename: Gerald
authors.initials: G
authors.lastname: Kehr
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.forename: Gerhard
authors.initials: G
authors.lastname: Erker
keywords: 1,1-carboboration; aryl migration; boron; hydride transfer; photolysis