Asymmetric hydroamination of aminoallenes catalyzed by titanium and tantalum complexes of chiral sulfonamide alcohol ligands
作者:Katherine E. Near、Brette M. Chapin、Diana C. McAnnally-Linz、Adam R. Johnson
DOI:10.1016/j.jorganchem.2010.08.001
日期:2011.1
A series of bidentate sulfonamide alcohol ligands with varying steric and electronic properties was synthesized. The titanium and tantalum complexes of these ligands, prepared in situ from either Ti(NMe2)(4) or Ta(NMe2)(5), were used as catalysts for the asymmetric hydroamination of 6-methyl-hepta-4,5-dienylamine, giving exclusively the alpha-vinylpyrrolidine product. The titanium derived catalysts gave products with low stereoselectivity, up to 11% ee favoring (+)-2-(2-methyl-propenyl)-pyrrolidine, while the tantalum derived catalysts gave products with higher and opposite stereoselectivity, up to 34% ee favoring (-)-2-(2-methyl-propenyl)-pyrrolidine. (C) 2010 Elsevier B.V. All rights reserved.