Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)]
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 5H 5)Fe(CO) (PPh 3)(COCHCHR)] have been studied to determine the extent of enantiorecognition in these reactions, and for the as...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
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2004
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| _version_ | 1826263565851426816 |
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| author | Davies, S Dupont, J Easton, R Ichihara, O McKenna, J Smith, A de Sousa, J |
| author_facet | Davies, S Dupont, J Easton, R Ichihara, O McKenna, J Smith, A de Sousa, J |
| author_sort | Davies, S |
| collection | OXFORD |
| description | 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 5H 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 5H 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 5H 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 5H 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. |
| first_indexed | 2024-03-06T19:53:49Z |
| format | Journal article |
| id | oxford-uuid:24dadef6-0535-4abf-8390-97b548120c0c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T19:53:49Z |
| publishDate | 2004 |
| record_format | dspace |
| spelling | oxford-uuid:24dadef6-0535-4abf-8390-97b548120c0c2022-03-26T11:52:29ZStereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)]Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:24dadef6-0535-4abf-8390-97b548120c0cEnglishSymplectic Elements at Oxford2004Davies, SDupont, JEaston, RIchihara, OMcKenna, JSmith, Ade Sousa, JThe 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 5H 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 5H 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 5H 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 5H 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. |
| spellingShingle | Davies, S Dupont, J Easton, R Ichihara, O McKenna, J Smith, A de Sousa, J Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)] |
| title | Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)] |
| title_full | Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)] |
| title_fullStr | Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)] |
| title_full_unstemmed | Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)] |
| title_short | Stereoselective conjugate addition reactions of lithium amides to alpha,beta-unsaturated chiral iron acyl complexes [(eta(5)-C5H5)Fe(CO)(PPh3)(COCH=CHR)] |
| title_sort | stereoselective conjugate addition reactions of lithium amides to alpha beta unsaturated chiral iron acyl complexes eta 5 c5h5 fe co pph3 coch chr |
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