Development of a Hypervalent Iodine Promoted One Step Formation of Tri- and Tetrasubstituted Cyclobutanes with Defined Relative and Absolute Configuration

该项目的目的是开发高价碘促进烯烃二聚，以实现对环丁烷产品的相对和绝对立体化学的完全控制。Donohoe Group已经表明，高价碘试剂将氟化溶剂中的富电子芳族反式烯烃氧化为自由基阳离子，其随后与未氧化的反式烯烃进行[2+2]环化。这导致形成同二聚体或异二聚体的全反式环丁烷。通过扩大底物范围和加强筛选的反应条件（氧化剂，溶剂，温度），我们将探讨的要求，烯烃成为氧化以及取代模式容忍的未氧化的alkene.The形成的所有反式环丁烷表明，使用的反式烯烃的初始几何形状保留在相应的产品。因此，我们计划研究烯烃几何构型对环丁烷产物的相对立体化学的影响。为此，我们将联合收割机将各种烯烃的几何构型相互结合起来，看看它们的立体化学是否被保留下来。通过优化反应条件，我们的目标是实现对转化的相对立体化学结果的控制。此外，我们将开发一种不对称环化反应。由于环化伙伴之一是带电的，提供了一种利用手性抗衡阴离子的新可能性，因为它可以选择性地与所形成的自由基阳离子形成离子对。手性抗衡阴离子可以在反应期间由所用的手性高价碘试剂形成，或者可以单独加入。最后，我们的目标是使用我们的不对称方法的关键手性环丁烷基序的天然产物，如Sceptrin家族成员的建设。

The aim of this project is the development of the hypervalent iodine promoted dimerisation of alkenes to achieve full control over the relative and absolute stereochemistry of the cyclobutane products. The Donohoe Group has shown that hypervalent iodine reagents oxidise electron-rich aromatic trans-alkenes in fluorinated solvents to radical cations, which subsequently undergo a [2+2] cyclisation with unoxidised trans-alkenes. This results in the formation of homo- or heterodimeric all-trans-cyclobutanes. By extension of the substrate scope and an enhanced screening of the reaction conditions (oxidant, solvent, temperature) we will explore the requirements for an alkene to become oxidised as well as the substitution pattern tolerated on the unoxidised alkene.The formation of all-trans-cyclobutanes shows that the initial geometry of the used trans-alkenes is retained in the corresponding products. Therefore, we plan to investigate the influence of the alkene geometries on the relative stereochemistry of the cyclobutane products. For this purpose, we will combine all kinds of alkene geometries with each other to see if their stereochemistry is retained. By optimising the reaction conditions, we aim to achieve control of the relative stereochemical outcome of the transformation.Furthermore, we will develop an asymmetric version of the cyclisation. Since one of the cyclisation partners is charged, a novel possibility to utilise a chiral counteranion is offered, because it can selectively form an ion pair with the formed radical cation. The chiral counteranion could be formed during the reaction from an employed chiral hypervalent iodine reagent or could be added separately. Finally, we aim to use our asymmetric methodology for the construction of key chiral cyclobutane motifs in natural products such as members of the Sceptrin family.