Merging Hydrogen Borrowing/Transfer Catalysis with Photochemistry

该项目属于EPSRC合成有机化学研究领域。借氢催化(HBC)已成为合成复杂分子的一种强有力的催化方法。一锅氧化还原序列具有内在的高原子经济性，以醇(或胺)为原料分子的烷基化反应会产生有价值的产品，而水(或氨)是唯一的副产品。这表明HBC是传统烷基化化学的一种绿色替代品。不幸的是，HBC通常需要较高的操作温度，导致相对于感兴趣的有机分子的其他敏感部分选择性较差(官能团耐受性较差)。另一种为反应提供足够能量而不使用如此高温的方法是使用高能照射或可见光介导光催化。可见光介导光催化(PC)已成为取代高能紫外光照射有机分子的一种强大且安全的替代方法。紫外线照射极其苛刻，官能团耐受性差，这意味着它不适合作为一般方法-可见光操作明显更安全和更有选择性。虽然已经探索了许多类型的化学可以从HBC中截取短寿命的氧化分子的产生，但使用光化学来做到这一点还没有。在这个项目中，我们的目标是将这两种技术结合起来，通过串联的借氢/转移光化学反应来生产复杂的有机分子。从而获得新的化学反应能力，并希望避免HBC通常恶劣的条件，创造一种更普遍和适用的方法，可供制药或农用化学品使用。首先，我们将研究新的反应模式，例如通过借氢事件(氧化或还原)创建对PC具有活性的短寿命分子的可行性。这种分子可以被光催化剂激发，并在最终的借氢事件(还原或氧化)完成催化循环之前与其他有机分子发生反应。同样，我们将寻求开发原则上既能执行有机分子的借氢事件又能进行光化学激发的催化剂。据我们所知，没有任何团体寻求合并HBC和PC，这在原则上可以改变借氢化学的格局，除了发现新的化学反应。

This project falls within the EPSRC Synthetic Organic Chemistry research area.Hydrogen borrowing catalysis (HBC) has emerged as a powerful catalytic method for the synthesis of complex molecules. The one-pot oxidation-reduction sequence has an intrinsic high atom economy and alkylation reactions using alcohols (or amines) as feedstock molecules lead to the production of valuable products and water (or ammonia) as the sole by-product. This presents HBC as a green alternative to traditional alkylation chemistry. Unfortunately, HBC typically requires high operating temperatures, leading to poor selectivity with respect to other sensitive parts of the organic molecule of interest (poor functional group tolerance). An alternative way of giving a reaction enough energy to proceed without using such high temperatures is by using high-energy irradiation or from visible light- mediated photocatalysis.Visible light-mediated photocatalysis (PC) has emerged as a powerful and safer alternative to high energy ultra violet light irradiation of organic molecules. Ultra-violet irradiation is extremely harsh and has poor functional group tolerance, meaning it is not suitable as a general method - visible light is significantly safer to operate with and more selective. Although many types of chemistry which can intercept the production of a short-lived oxidised molecules from HBC have been explored, using photochemistry to do so has not. In this project we will aim to combine the two technologies to produce complex organic molecules via tandem hydrogen borrowing/transfer photochemical reactions. Thereby deriving new chemical reactivity and also looking to avert the typically harsh conditions of HBC, creating a more generalised and applicable method which could be used by the pharmaceutical or agrochemical communities.First we will investigate new modes of reactivity, such as the feasibility of creating a short-lived molecule, which is active to PC from a hydrogen-borrowing event (oxidation or reduction). This molecule could be excited by a photocatalyst and undergo a reaction with other organic molecules before a final hydrogen borrowing event (reduction or oxidation) can complete the catalytic cycle. Similarly, we will look to develop catalysts which could in principle perform both the hydrogen borrowing events and photochemical excitation of the organic molecules. To our knowledge, no groups have looked to merge HBC and PC, which in principle could transform the landscape of hydrogen borrowing chemistry in addition to discovering novel chemical reactivity.