Diastereoselective Intramolecular Carbolithiations of Stereodefined Secondary Alkyllithiums Bearing a Remote Alkynylsilane.

Various secondary alkyl iodides bearing a remote alkynylsilane underwent intramolecular carbolithiations triggered by an I/Li-exchange performed at -100 °C using t-BuLi (2.5 equiv). The resulting alkenyllithiums were stereoselectively converted to tetrasubstituted cyclopentane exo-alkylidenes. After Pd-catalyzed hydrogenation, cyclopentanes and cis-bicyclo[4.3.0]nonanes were obtained with stereocontrol of four contiguous centers.