(-)-Sparteine-mediated stereoselective intramolecular carbolithiation of alkynes

Article abstract of DOI:10.1016/S0040-4039(98)00085-9

The asymmetric deprotonation mediated by the chiral base s- butyllithium/(-)-sparteine of 4-substituted 5-hexynyl carbamates permits the synthesis of enantioenriched carbanionic pairs which undergo a regioselective 5-exo-dig ring closure with the triple bond acting as an internal electrophile. The functionalized five-membered rings are formed with complete stereoselectivity in high yields.