Effect of ligand structure on the asymmetric cyclization of achiral olefinic organolithiums

The ability of a large and chemically diverse set of 30 chiral ligands to effect asymmetric cyclization of 2-(N,N-diallylamino)phenyllithium (1), derived from N,N-diallyl-2-bromoaniline (2) by low-temperature lithium-bromine exchange, has been investigated in an attempt to elucidate the structural motifs required to provide high enantiofacial selectivity in the ring closure. Although none of the ligands examined in this study afforded 1-allyl-3-methylindoline in significantly higher ee than previously observed for the cyclization of 1 in the presence of the benchmark ligand (-)-sparteine, several ligands, structurally unrelated to sparteine and available in either enantiomeric form, were found to match the utility of (-)-sparteine in this chemistry.