Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

The conjugate additions of a range of achiral and homochiral lithium amides derived from primary and secondary amines to α,β-unsaturated chiral iron acyl complexes [(η 5 -C 5 H 5 )Fe(CO) (PPh 3 )(COCHCHR)] have been studied to determine the extent of enantiorecognition in these reactions, and for the asymmetric synthesis of β-amino acids and β-lactams. Conjugate addition of achiral lithium dimethylamide to the chiral iron cinnamoyl complexes (S,E)- and (S,Z)-[(η 5 -C 5 H 5 )Fe(CO)(PPh 3 )(COCHCHPh)] proceeds with high diastereoselectivity, with this protocol being used to establish unambiguously the absolute configuration of Winterstein's acid (3-N,N-dimethylamino-3-phenylpropanoic acid) as (R). The highly diastereoselective conjugate addition of lithium N-benzyl-N- trimethylsilylamide to a range of α,β-unsaturated iron acyl complexes, followed by in-situ elaboration of the derived enolate by either alkylation or aldol reactions is also demonstrated, facilitating the stereoselective synthesis of both cis- and trans-β-lactams. This methodology has been used to effect the formal asymmetric syntheses of (±)-olivanic acid and (±)-thienamycin. Addition of chiral lithium amides derived from primary and secondary amines to the iron crotonyl complex [(η 5 -C 5 H 5 )Fe(CO)(PPh 3 )(COCHCHMe) ] indicates that lithium N-α-methylbenzylamide shows low levels of enantiorecognition, while lithium N-3,4-dimethoxybenzyl-N-α- methylbenzylamide and lithium N-benzyl-N-α-methylbenzylamide show high levels of enantiodiscrimination. The high level of observed enantiorecognition was used to facilitate a kinetic resolution of (RS)-[(η 5 -C 5 H 5 )Fe(CO)(PPh 3 )(COCHCHMe)] with homochiral lithium (R)-N-3,4-dimethoxybenzyl-N-α-methylbenzylamide. Further mechanistic studies show that conjugate additions of (RS)-lithium N-benzyl-N-α-methylbenzylamide to either the (RS)- or homochiral iron crotonyl complex show 2:1 stoicheiometry, while homochiral lithium N-benzyl-N-α-methylbenzylamide shows 1:1 stoicheiometry. © 2004 Elsevier B.V. All rights reserved.

Original publication

DOI

10.1016/j.jorganchem.2004.04.046

Type

Journal article

Journal

Journal of Organometallic Chemistry

Publication Date

29/11/2004

Volume

689

Pages

4184 - 4209