Silver(I)-catalysed Synthesis of Cuneanes from Cubanes and their Investigation as Isosteres

利用光催化来驱动化学反应已经成为一种开发更环保、更可持续的化学合成的有力方法。十钨酸盐是一种具有光活性的多金属氧酸盐（POM）化合物，由于它避免了在类似催化剂中常见的贵金属的使用，并且能够介导多种有价值的C-H功能化反应，因此在有机化学中作为光催化剂显示出很大的前景。它也显示出在复杂分子后期功能化的适用性，这是一种新兴的策略，使生物活性分子的高效衍生化。尽管近年来人们对十钨酸盐介导的h原子转移反应产生了兴趣和发展，但它的使用存在许多缺点。这种光催化剂仅在紫外光下具有活性，这在有机合成中具有实际局限性，并且复杂分子中的C-H键选择性可以受到限制。为了进一步扩大这种有前途的催化系统的范围，这些缺点需要得到缓解。尽管文献中报道的POM化合物种类繁多，十钨酸盐仍然是有机化学中唯一一种用作C-H功能化光催化剂的化合物。因此，POMs作为光催化剂在有机化学中的应用有很大的发展空间。提出的解决方案和方法牛顿小组对各种“杂化”多金属氧酸盐结构的设计和合成进行了广泛的研究，这些结构具有有机配体附着在POM簇上。这些化合物具有与十钨酸盐相似的光化学特性，因此可能适用于类似的C-H活化化学，但由于有机修饰而具有更大的可调性。这些有机修饰可能允许修改POM簇的能级以允许在可见光下的活性，或者允许添加对反应选择性施加更大控制的超分子结合元件。这些可能性将在这个博士项目中进行研究。在此之前，已经证明了金属团簇的HOMO / LUMO水平的调节是使用POM和有机配体之间的膦酸盐键。这项工作将通过设计和合成一系列新型混合POM结构来扩展，这些结构将使用包括核磁共振、循环伏安法和紫外/可见光谱在内的一系列技术进行全面表征。该项目的主要目标是证明混合POMs作为C-H活化催化剂的适用性和实用性，因此新催化剂将在一系列光化学反应中进行测试，以克服十钨酸盐的一些缺点。除此之外，还将进一步探索使用十钨酸盐的新化学反应，以扩大这种有前途的光催化剂的范围。

Using light to drive chemical reactions via photocatalysis has emerged as a powerful method in the effort to develop greener, more sustainable chemical synthesis. Decatungstate, a photoactive polyoxometalate (POM) compound, has shown great promise as a photocatalyst in organic chemistry as it avoids the use of precious metals common in similar catalysts and is able to mediate a variety of valuable C-H functionalisation reactions. It has also shown applicability in the late-stage functionalisation of complex molecules, which is an emerging strategy for enabling highly efficient derivatization of bioactive molecules.Despite the interest in and development of decatungstate-mediated H-atom transfer reactions in recent years, there are a number of drawbacks to its use. This photocatalyst is only active in ultraviolet light, which has practical limitations in organic synthesis, and C-H bond selectivities in complex molecules can be limited. These drawbacks need to be mitigated in order to further broaden the scope of this promising catalytic system. Despite the enormous diversity of POM compounds reported in the literature, decatungstate remains the only one in use as a C-H functionalisation photocatalyst in organic chemistry. There is therefore significant scope to further explore the application of POMs as photocatalysts in organic chemistry.Proposed solution and methodologyThe design and synthesis of various 'hybrid' polyoxometalate structures, which have organic ligands attached to the POM cluster, has been investigated extensively by the Newton group. These compounds have similar photochemical characteristics to decatungstate and may therefore be amenable to similar C-H activation chemistry, but with greater tunability due to organic modifications. These organic modifications may allow the energy levels of the POM cluster to be modified to allow for activity in visible light, or allow the addition of supramolecular binding elements that exert greater control over reaction selectivity. These possibilities will investigated in this PhD project.Previously, tuning of the metal cluster's HOMO / LUMO levels has been demonstrated using phosphonate linkages between the POM and organic ligand. This work will be expanded by designing and synthesizing a range of novel hybrid POM structures that will be fully characterised using a range of techniques including NMR, cyclic voltammetry and UV/Vis spectroscopy. The major goal of the project is to demonstrate the applicability and practicality of hybrid POMs as C-H activation catalysts, and the new catalysts will be therefore be tested in a range of photochemical reactions with the aim over overcoming some of the drawbacks of decatungstate. Alongside this, further novel chemistry using decatungstate will also be explored to expand the scope of this promising photocatalyst.