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

研究的总体目标是了解铂(II)和钯(II)在一个合作的同手性双金属催化剂体系中的相互作用，以便能够将这种作用模式转移并应用于其他相关的反应类型。Pallada-和铂环的分子内合作应该导致催化反应的发展，其中烯烃部分被表面选择性地激活以备亲核试剂的攻击，而亲核试剂本身是由催化剂(例如通过C-H活化或烯醇化)产生的。异双金属金属环应该允许通过协同活化模式来实现高反应活性和立体选择性，该模式利用了底物分子在催化位置的特定位置的特定取向。选择铂(II)是为了延长有效的(但可逆的)烯烃配位的寿命，从而(取决于反应类型)实现催化反应的整体加速。PD中心的存在应在I.A.通过某种络合作用加速了铂上的烯烃配位。应针对两种不同的反应类型研究两种金属中心的协同效应：(1)通过Friedel-Craft烷基化(也称为氢芳基化)形成具有生物意义的四氢咔唑；(2)通过SN2(素数)机制进行区域、非对映和对映体选择性的正式烯丙基取代，同时控制生成的立体中心在烯丙基底物(第三中心)和新的C-C键中的亲核中心(第四中心)的构型。

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.