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[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.

We report a method for the synthesis of chiral pyrrolidines using tin-lithium exchange and cyclization reactions. The precursors are formed readily from simple starting materials and undergo tin-lithium exchange by treatment with n-butyllithium. Subsequent intramolecular carbolithiation is stereoselective to give highly enantiomerically enriched pyrrolidines in excellent yields.

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