Readily Accessible 1,2-Amino Ether Ligands for Enantioselective Intramolecular Carbolithiation
摘要:
A new class of chiral 1,2-amino ether ligands, readily accessible from naturally occurring alpha-amino- or alpha-hydroxy acids, was found to provide high levels of both conversion and stereocontrol (up to 95:5 er) in intramolecular carbolithiation reactions, outperforming the benchmark ligand (-)-sparteine. The ligand could, be used in a substoichiometric amount (0.25 equiv) without significant loss of enantios electivity.
A new class of chiral 1,2-amino ether ligands, readily accessible from naturally occurring alpha-amino- or alpha-hydroxy acids, was found to provide high levels of both conversion and stereocontrol (up to 95:5 er) in intramolecular carbolithiation reactions, outperforming the benchmark ligand (-)-sparteine. The ligand could, be used in a substoichiometric amount (0.25 equiv) without significant loss of enantios electivity.
Effect of Ligand Structure on the Asymmetric Cyclization of Achiral Olefinic Organolithiums
作者:Michael J. Mealy、Matthew R. Luderer、William F. Bailey、Michael Bech Sommer
DOI:10.1021/jo049477+
日期:2004.9.1
The ability of a large and chemically diverse set of 30 chiral ligands to effect asymmetriccyclization 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