THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME]
Michael addition of methyllithium to the E-crotonyl complex (RS)-[η5-C5H5)Fe(CO)-(PPh3 )COCHCHMe] followed by trapping of the resultant enolate with methyl iodide gives (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH(Me)CHMe2] (d.e. > 100:1), also generated by treatment of (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH2C...
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格式: | Journal article |
語言: | English |
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1986
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author | Davies, S Dordorhedgecock, I Sutton, K Walker, J Jones, R Prout, K |
author_facet | Davies, S Dordorhedgecock, I Sutton, K Walker, J Jones, R Prout, K |
author_sort | Davies, S |
collection | OXFORD |
description | Michael addition of methyllithium to the E-crotonyl complex (RS)-[η5-C5H5)Fe(CO)-(PPh3 )COCHCHMe] followed by trapping of the resultant enolate with methyl iodide gives (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH(Me)CHMe2] (d.e. > 100:1), also generated by treatment of (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH2CH(OMe)2] with three equivalents of methyllithium and methyl iodide. Addition of n-butyllithium to the (RS)-E-crotonyl complex followed by protonation with methanol occurs with high diastereoselectivity. Quenching with methyl iodide gives (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH(Me)CH(Me)n-Bu], also generated by treating either diastereoisomer of [(η5C5H5)Fe(CO)(PPh3)COC H2CH(Me)OMe] with two equivalents of n-butyllithium and methyl iodide. Decomplexatlon gives the known erythro-2,3-dimethyl-heptanoic acid. Similarly, Michael addition of lithium benzylamide and electrophilic quenching with methanol or methyl iodide occurs with high diastereoselectivity and gives upon decomplexation, 4-methyl- and cis-3,4-dimethyl-N-benzyl-β-lactams respectively. The stereochemical results are rationalised by addition occurring to the E-crotonyl complex in the anti (CO to CO) and cisoid conformation and subsequent alkylation of the unhindered face of the E-enolate generated. Confirmation is provided by an X-ray crystal structure analysis of (RS)-E-[(η5-C5H5)Fe(CO)(PPh3 )COCHCHMe]. When repeated with the optically pure (S)-E-crotonyl complex, decomplexation gives essentially optically pure (2R),(3R)-(-)-N-benzyl-2,3-dimethylheptanamide, (4S)-(-)-4-methyl- and (3R),(4S)-(-)-cis-3,4-dimethyl-N-benzyl-β-lactams. © 1986. |
first_indexed | 2024-03-07T05:47:43Z |
format | Journal article |
id | oxford-uuid:e7c611a0-b94e-4c79-8560-b0ef6a470a0e |
institution | University of Oxford |
language | English |
last_indexed | 2024-03-07T05:47:43Z |
publishDate | 1986 |
record_format | dspace |
spelling | oxford-uuid:e7c611a0-b94e-4c79-8560-b0ef6a470a0e2022-03-27T10:41:32ZTHE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME]Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:e7c611a0-b94e-4c79-8560-b0ef6a470a0eEnglishSymplectic Elements at Oxford1986Davies, SDordorhedgecock, ISutton, KWalker, JJones, RProut, KMichael addition of methyllithium to the E-crotonyl complex (RS)-[η5-C5H5)Fe(CO)-(PPh3 )COCHCHMe] followed by trapping of the resultant enolate with methyl iodide gives (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH(Me)CHMe2] (d.e. > 100:1), also generated by treatment of (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH2CH(OMe)2] with three equivalents of methyllithium and methyl iodide. Addition of n-butyllithium to the (RS)-E-crotonyl complex followed by protonation with methanol occurs with high diastereoselectivity. Quenching with methyl iodide gives (RS)-[(η5-C5H5)Fe(CO)(PPh3 )COCH(Me)CH(Me)n-Bu], also generated by treating either diastereoisomer of [(η5C5H5)Fe(CO)(PPh3)COC H2CH(Me)OMe] with two equivalents of n-butyllithium and methyl iodide. Decomplexatlon gives the known erythro-2,3-dimethyl-heptanoic acid. Similarly, Michael addition of lithium benzylamide and electrophilic quenching with methanol or methyl iodide occurs with high diastereoselectivity and gives upon decomplexation, 4-methyl- and cis-3,4-dimethyl-N-benzyl-β-lactams respectively. The stereochemical results are rationalised by addition occurring to the E-crotonyl complex in the anti (CO to CO) and cisoid conformation and subsequent alkylation of the unhindered face of the E-enolate generated. Confirmation is provided by an X-ray crystal structure analysis of (RS)-E-[(η5-C5H5)Fe(CO)(PPh3 )COCHCHMe]. When repeated with the optically pure (S)-E-crotonyl complex, decomplexation gives essentially optically pure (2R),(3R)-(-)-N-benzyl-2,3-dimethylheptanamide, (4S)-(-)-4-methyl- and (3R),(4S)-(-)-cis-3,4-dimethyl-N-benzyl-β-lactams. © 1986. |
spellingShingle | Davies, S Dordorhedgecock, I Sutton, K Walker, J Jones, R Prout, K THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME] |
title | THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME] |
title_full | THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME] |
title_fullStr | THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME] |
title_full_unstemmed | THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME] |
title_short | THE ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS - STEREOCONTROLLED ASYMMETRIC TANDEM MICHAEL ADDITIONS AND SUBSEQUENT ALKYLATIONS OF E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CHME] - X-RAY CRYSTAL-STRUCTURE OF (RS)-E-[(ETA-5-C5H5)FE(CO)(PPH3)COCH - CHME] |
title_sort | asymmetric synthesis of beta lactams stereocontrolled asymmetric tandem michael additions and subsequent alkylations of e eta 5 c5h5 fe co pph3 coch chme x ray crystal structure of rs e eta 5 c5h5 fe co pph3 coch chme |
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