title: Synthesis of an ethynyl carbamate and application for enantioselective cyclocarbolithiation.
abstract: [reaction: see text] The intramolecular trans-cyclocarbolithiation of the alpha-lithiated 4-substituted 5-hexynyl carbamate (1S,4RS)-14 employing lithiodestannylation is presented. The 5-exo-dig cyclization products cis-/trans-16a were formed exclusively. The highly enantioenriched organotin precursor (S)-11 was synthesized via an asymmetric deprotonation of the corresponding alkyl carbamate 10 by the chiral complex sec-butyllithium/(-)-sparteine and subsequent substitution with tributyltin chloride.
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Gralla
authors.forename: Birgit
authors.initials: B
authors.lastname: Wibbeling
authors.forename: Dieter
authors.initials: D
authors.lastname: Hoppe