Asymmetric Hetero-Dinuclear Catalysis via Cooperation of Platinum(II) and Palladium(II) for the Stereoselective Formation of Quaternary Stereocenters

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The overall goal of the proposed studies is to understand the interplay of Pt(II) and Pd(II) within a cooperative homochiral bimetallic catalyst system to be able to transfer and apply this mode of action to other related reaction types. The intramolecular cooperation of pallada- and platinacycles should result in the development of catalytic reactions, in which an olefin moiety is face-selectively activated for the attack by a nucleophile, which itself is generated by the catalyst (for instance by C-H acitivation or enolization). The heterobimetallic metallacycles should allow for high reactivity and stereoselectivity by the cooperative activation mode taking advantage from a defined orientation of the substrate molecules at defined positions at the catalytical sites. Pt(II) has been chosen to extend the lifetime of a productive (yet reversible) olefin coordination and thus (depending on the reaction type) to achieve an overall acceleration of the catalytic reactions. The presence of the Pd center shall i.a. accelerate the olefin coordination at Pt by some sort of a chelate effect. The synergistic effect of both metal centers shall be investigated for two different reaction types: (1) the formation of biologically interesting tetrahydrocarbazoles via Friedel-Crafts alkylations (also called hydroarylations) and (2) the regio-, diastereo- and enantioselective formal allylic substitution via an SN2(prime)-mechanism, simultaneously controlling the configuration of the generated stereocenters at the allylic substrate (tertiary center) and at the nucleophile (quaternary center) in a new C-C bond.