Design, synthesis, and application of novel chiral ONN ligands for asymmetric alkylation
摘要:
Starting from easily available chiral pool amino alcohols, a set of novel chiral ONN ligands was synthesized and their catalytic potential was examined in asymmetric alkylation. Ligands with a secondary central NH group and N-methylated ONN ligands were successfully applied as catalysts in the addition of diethyl zinc to various aromatic aldehydes, yielding secondary alcohols in excellent yields of up to 99 % ee.
Enantioselective Alkylation of Aldehydes with Diethylzinc Catalyzed by C<sub>2</sub>-Symmetric Ligands
作者:David Williams、Mark Fromhold
DOI:10.1055/s-1997-6125
日期:1997.6
The C2-symmetric pyridine 1, incorporating two units of (-)-ephedrine, is an effective catalyst for the enantioselective reactions of diethylzinc with a series of aromatic aldehydes. The propanol products possess the S-configuration. This result is a significant reversal of stereochemistry based upon literature precendents and our direct comparisons with reactions catalyzed by the corresponding C2-symmetric xylene 2.
Enantioselective diethylzinc addition to aldehydes catalyzed by Ti(IV) complex of unsymmetrical chiral bis(sulfonamide) ligands of trans-cyclohexane 1,2-diamine
作者:Alakesh Bisai、Pradeep K. Singh、Vinod K. Singh
DOI:10.1016/j.tet.2006.11.022
日期:2007.1
Titanium(IV) complexes of bidentate trans-cyclohexane 1,2-diamine-based unsymmetrical chiral bis(sulfonamide) ligands were evaluated as catalysts for the asymmetric addition of diethylzinc to aldehydes. The reaction provided secondary alcohols in quantitative yields and very good enantioselectivity (up to 96% ee).
A Schiff's base ligand with a trifluoromethyl carbinol moiety was synthesized, and a structure of the active complex for asymmetric induction on the reaction of diethylzinc with aldehydes is proposed. (c) 2006 Published by Elsevier Ltd.
Design, synthesis, and application of novel chiral ONN ligands for asymmetric alkylation
Starting from easily available chiral pool amino alcohols, a set of novel chiral ONN ligands was synthesized and their catalytic potential was examined in asymmetric alkylation. Ligands with a secondary central NH group and N-methylated ONN ligands were successfully applied as catalysts in the addition of diethyl zinc to various aromatic aldehydes, yielding secondary alcohols in excellent yields of up to 99 % ee.