Enantioselective C–C bond formation in styrene dimerization with chiral ansa zirconocene-based catalyst

In the presence of hydrogen and of (R,R)-ethylenebis tetrahydroindenyl zirconium dichloride activated by methylalumoxane, the styrene can be fully converted into low molecular weight compounds. The kinetic picture of the hydrooligomers formation is made complicated by the irregular regiochemistry of the styrene insertion. However the study on the effect of the feed composition on the products composition allows inferring mechanistic hypothesis and optimizing the formation of the chiral product, (R)-1,3-diphenylbutane. The subsequent functionalization of this molecule, without loss of chirality, discloses the potentiality of such kind of catalytic system for the synthesis of optically active synthones.

The mixture of styrene and H2 in the presence of the chiral ansa zirconocene (R,R)-ethylenebis tetrahydroindenyl zirconium dichloride and methylalumoxane affords optically active (R)-1,3-diphenylbutane (1,3-dpb). This product can be functionalized without loss of chirality, e.g. to 2-methylglutaric acid. The study on the complex regiochemical behavior of this hydrooligomerization catalysis allowed the optimization of the 1,3-dpb yield and suggests the possible improvement of the catalyst performance. Figure optionsDownload as PowerPoint slide