title: Lithium Bromide/Water as Additives in Dearomatizing Samarium-Ketyl (Hetero)Arene Cyclizations.
abstract: New conditions for dearomatizing samarium-ketyl (hetero)arene cyclizations are reported. In many examples of these samarium diiodide-mediated reactions, lithium bromide and water can be used as additives instead of the carcinogenic and mutagenic hexamethylphosphoramide (HMPA). The best results were obtained for the cyclizations of N-acylated indole derivatives delivering the expected indolines in good yields and excellent diastereoselectivities. A new type of cyclization delivering indolyl-substituted allene derivatives is also described. The scope and limitations of the lithium bromide/water system are discussed.
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany).
authors.forename: Chintada Nageswara
authors.initials: CN
authors.lastname: Rao
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany).
authors.forename: Christoph
authors.initials: C
authors.lastname: Bentz
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany). hans.reissig@chemie.fu-berlin.de.
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Reissig
keywords: cyclization; indoles; radicals; reductions; samarium diiodide; solvent effects