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 5)FE(CO)(PPH3)COCH2CH2C(CN)(IPR)-[3,4-C6H3(OME)2])

Michael addition of the anion of 3,4-dimethoxy-alpha-isopropylbenzenea cetonitrile, 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 diastereome rically pure (R(Fe)R(C))- and 5)Fe(CO)(PPh3)COCH2CH2C(CN)(iPr)[3,4-C6H 3-(OMe)2]} after fractional crystallization. The absolute configuratio n of the newly formed stereogenic carbon atom in these complexes was e stablished by X-ray crystallography. The enantiomerically pure (S)-(-) - and cyano-3,4-dimethoxy-gamma-isopropylbenzenebutanoic acids, precur sors for the drug verapamil, were obtained on decomplexation by treatm ent with bromine/water. In the Michael reaction, the new bis-addition product (iPr)[3,4-C6H3(OMe)2]][CO(PPh3)(CO)Fe(eta5-C5H5)]} was formed as a byproduct, which, after decomplexation, gave the alpha-substitute d glutaric acid -2-(3,4-dimethoxyphenyl)-2-isopropylethyl]glutaric aci d. Michael addition of the anion of 3,4-dimethoxybenzeneacetonitrile, having a H substituent at the carbanionic C atom, to the acryloyl comp lex (S(Fe))-[(eta5-C5H5)Fe(CO)(PPh3)COCH=CH2] gave the alpha-enolate - C5H5)Fe(CO)(PPh3)COCHCH2CH(CN)[3,4-C6H3(OMe)2]}-, which transformed to the anion -C5H5)Fe(CO)(PPh3)COCH2CH2C(CN)[3,4-C6H3(OMe)2]}-, having t he negative charge at the gamma-position. This anion added again to th e acryloyl complex to build up the bis-addition product -C5H5)Fe(CO)(P Ph3)COCH2CH2]2C(CN)[3,4-C6H3(OMe)2]} after protonation. In addition, a further acryloyl complex added to the enolate of this complex. In thi s way the tris-addition product -C5H5)Fe(CO)(PPh3)COCH2CH2C(CN)[3,4-C6 H3(OMe)2]CH2 (CO)(PPh3)(eta5-C5H5)][COFe(CO)(PPh3)(eta5-C5H5)]} was sy nthesized with three (S(Fe))-(eta5-C5H5)Fe(CO)(PPh3) substituents and two diastereomerically pure stereogenic carbon atoms.