ASYMMETRIC DEPROTONATIONS - LITHIATION OF N-(TERT-BUTOXYCARBONYL)INDOLINE WITH SEC-BUTYLLITHIUM (-)-SPARTEINE/

The asymmetric lithiation of N-Boc indoline (1) with s-BuLi/(-)-sparte ine and subsequent substitution provides the 2-substituted N-Boc indol ines 3 and 5-11 with excellent enantiomeric ratios and in variable yie lds. The asymmetric lithiation-substitution sequence with N-Boc-7-chlo roindoline (12) provides products 13-19 with good enantiomeric ratios. Mechanistic investigation establishes that the enantioselectivities a rise from an initial asymmetric deprotonation to provide the enantioen riched and configurationally stable organolithium intermediates (S)-28 and (S)-29, which react stereoselectively with electrophiles.