The asymmetric synthesis of phosphorus- and sulfur-containing tricarbonyl(η6-arene)chromium complexes using the chiral base approach

Abstract

The use of a simple chiral lithium amide base 2 enables the asymmetric transformation of tricarbonyl[η6-(diphenylphosphinoyl)benzene]chromium(0) 12 into the corresponding ortho-silylated complex in up to 86% ee. A tin derivative was prepared similarly and was then used to prepare other derivatives via reduction to the corresponding phosphine, followed by transmetallation–electrophilic quench. In the case of tricarbonyl(η6-1,3-dihydroisobenzothiophene)chromium(0) the chiral base 2 was ineffective, and it was necessary to use a bis-lithium amide base 9 to effect asymmetric substitution in high ee (up to 95%). Decomplexation gave the corresponding chiral sulfides in highly enantiomerically enriched form. In all cases the absolute stereochemistry of the products was derived by conducting X-ray structure determinations on selected examples.