Intramolecular Carbolithiation Reactions for the Synthesis of 2,4-Disubstituted Tetrahydro-quinolines: Evaluation of TMEDA and (−)-Sparteine as Ligands in the Stereoselectivity † Dedicated to Prof. Josep Font on the occasion of his 70th birthday.

Abstract

The preparation of 4-substituted 2-phenyltetrahydroquinolines from N-alkenylsubstituted 2-iodoanilines via intramolecular carbolithiation reactions has been investigated. The stereochemical outcome of the carbolithiation reactions depends on the nature of organolithium employed to perform the lithium-halogen exchange, the solvent, or the use of additives, for example, TMEDA or chiral bidentated ligands such as (-)-sparteine. Thus, the 2,4-disubstituted tetrahydroquinolines are obtained with moderate diastereoselectivities (up to 77:23) and with ee up to 94% when Weinreb amide derivatives are used (R = CONMe(OMe)).