BRUNNER, H and FORSTER, S and NUBER, B (1993) OPTICALLY-ACTIVE TRANSITION-METAL COMPLEXES .104. ASYMMETRIC MICHAEL REACTIONS OF (RFE)-[(ETA-5-C5H5)FE(CO)(PPH3)COCH=CH2] AND (SFE)-[ETA(5)-C5H5)FE(CO)(PPH3)COCH=CH2] - SYNTHESIS OF AN ENANTIOMERICALLY PURE PRECURSOR FOR VERAPAMIL - X-RAY CRYSTAL-STRUCTURE OF (RFERC)-((ETA-C5H5)FE(CO)(PPH3)COCH2CH2C(CN)(IPR)-[3,4-C6H3(OME)2]). ORGANOMETALLICS, 12 (10). pp. 3819-3827. ISSN 0276-7333,
Full text not available from this repository.Abstract
Michael addition of the anion of 3,4-dimethoxy-alpha-isopropylbenzeneacetonitrile, having no H substituent at the carbanionic C atom, to the acryloyl complexes (R(Fe))- and (S(Fe))-[(eta5-C5H5)Fe(CO)(PPH3)COCH=CH2] followed by protonation of the resulting enolate gave diastereomerically pure (R(Fe)R(C))- and (S(Fe)S(C))-{(eta5-C5H5)Fe(CO)(PPh3)COCH2CH2C(CN)(iPr)[3,4-C6H3-(OMe)2]} after fractional crystallization. The absolute configuration of the newly formed stereogenic carbon atom in these complexes was established by X-ray crystallography. The enantiomerically pure (S)-(-)- and (R)-(+)-gamma-cyano-3,4-dimethoxy-gamma-isopropylbenzenebutanoic acids, precursors for the drug verapamil, were obtained on decomplexation by treatment with bromine/water. In the Michael reaction, the new bis-addition product {(eta5-C5H5)Fe(CO)(PPh3)COCH2CH2CH[CH2C(CN)(iPr)[3,4-C6H3(OMe)2]][CO(PPh3)(CO)Fe(eta5-C5H5)]} was formed as a byproduct, which, after decomplexation, gave the alpha-substituted glutaric acid alpha-[2-cyano-2-(3,4-dimethoxyphenyl)-2-isopropylethyl]glutaric acid. Michael addition of the anion of 3,4-dimethoxybenzeneacetonitrile, having a H substituent at the carbanionic C atom, to the acryloyl complex (S(Fe))-[(eta5-C5H5)Fe(CO)(PPh3)COCH=CH2] gave the alpha-enolate (S(Fe))-{(eta-C5H5)Fe(CO)(PPh3)COCHCH2CH(CN)[3,4-C6H3(OMe)2]}-, which transformed to the anion (S(Fe))-{(eta5-C5H5)Fe(CO)(PPh3)COCH2CH2C(CN)[3,4-C6H3(OMe)2]}-, having the negative charge at the gamma-position. This anion added again to the acryloyl complex to build up the bis-addition product (S(Fe)S(Fe))-{[(eta5-C5H5)Fe(CO)(PPh3)COCH2CH2]2C(CN)[3,4-C6H3(OMe)2]} after protonation. In addition, a further acryloyl complex added to the enolate of this complex. In this way the tris-addition product {(eta5-C5H5)Fe(CO)(PPh3)COCH2CH2C(CN)[3,4-C6H3(OMe)2]CH2 CH[CH2CH2COFe(CO)(PPh3)(eta5-C5H5)][COFe(CO)(PPh3)(eta5-C5H5)]} was synthesized with three (S(Fe))-(eta5-C5H5)Fe(CO)(PPh3) substituents and two diastereomerically pure stereogenic carbon atoms.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CHIRAL AUXILIARY (ETA-5-C5H5)FE(CO)(PPH3); ACYL LIGANDS; SUBSEQUENT ALKYLATIONS; BETA-LACTAMS; ADDITIONS; REACTIVITY; |
| Depositing User: | Dr. Gernot Deinzer |
| Last Modified: | 19 Oct 2022 08:42 |
| URI: | https://pred.uni-regensburg.de/id/eprint/53752 |
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