Asymmetric synthesis of 2-alkenyl-1-cyclopentanols via tin-lithium exchange and intramolecular cycloalkylation.
[reaction: see text] We report a method for the synthesis of chiral cyclopentanes using tin-lithium exchange and cycloalkylation reactions. The sec-butyllithium/(-)-sparteine-mediated deprotonation of an alkyl carbamate and subsequent substitution furnishes a highly enantioenriched stannane as a stable carbanion equivalent. It was transformed into suitable cyclization precursors, which underwent tin-lithium exchange and stereoselective cycloalkylation when reacted with n-butyllithium, giving highly enantioenriched cyclopentanes in very good yields. A kinetic resolution was observed with a higher substituted stannane.
Christoph
Guido
G
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany.
Hoppe
Dieter
D