Development of excited-state bond homolysis as a key step for Ni catalysis

能够合成复杂分子支架的键构建方法是本领域技术人员的关键兴趣。 医药行业。为此，Ni催化已经成为构建C（sp2）- C（sp2）、C（sp3）-C（sp2）和C（sp3）-C（sp3）键。倪成功地完成了这些转变， 在镍从事单电子和双电子过程的能力-通过0，I，II和III氧化循环 states.因此，除了典型的双电子过程（迁移插入，b-氢化物消除， 等等），基本的步骤，如抽象，自由基捕获，电子转移，经常遇到的， Ni催化。镍催化也是一个富有成效的平台，为光化学的整合过渡- 金属催化最近，我们的研究小组发现，在光照射下，芳基NiII（bpy）配合物可以发生 激发态键均裂以产生C（sp2）自由基。这些初步的化学计量研究表明， 光能可以选择性地引导到Ni，以从原料化学品中产生高活性中间体 前体我们建议利用光消除从镍作为一个通用的步骤，在镍催化。 传统的交叉偶联反应的发展集中在从序列中获得新的结果 已知的基本过程。这项建议是独一无二的，因为它是基于一个新的发展， 镍催化的基础步骤。我们的努力将利用单电子和双电子之间的相互作用 方法可访问的镍，以解决在选择性和反应性的限制，在本文献中。的 本文所述的研究将包括三个目标：（1）开发提高量子效率的方法。 激发态Ni键均裂过程的产率;（2）探索和扩展有机自由基中心的范围 （3）采用光消除作为Ni催化的基本步骤。所有三 这些方面将同时进行探索，共同代表第一排领域令人兴奋的新方向 过渡金属催化

Methods for bond construction enabling the synthesis of complex molecular scaffold are of key interest to the pharmaceutical industry. To this end, Ni catalysis has emerged as a versatile tool for the construction of C(sp2)– C(sp2), C(sp3)–C(sp2), and C(sp3)–C(sp3) bonds. The success of Ni in accomplishing these transformations lies in the ability of Ni to engage in both single- and two-electron processes – cycling through 0, I, II, and III oxidation states. As a result, in addition to canonical two-electron processes (migratory insertion, b-hydride elimination, etc.), fundamental steps such as abstractions, radical captures, and electron transfers are often encountered in Ni catalysis. Ni catalysis has also served as a fruitful platform for the integration of photochemistry in transition- metal catalysis. Recently, our group found that upon irradiation with light, aryl NiII(bpy) complexes can undergo excited-state bond homolysis to generate C(sp2) radicals. These initial stoichiometric studies demonstrate that light energy can be selectively directed to Ni to generate highly reactive intermediates from feedstock chemical precursors. We propose leveraging photoelimination from NiII as a general step to be employed in Ni catalysis. Traditional development of cross-coupling reactions focuses around achieving new outcomes from sequences of known fundamental processes. This proposal is unique as it is based on the development of a new fundamental step for Ni catalysis. Our efforts will capitalize on the interplay between single- and two- electron processes accessible to Ni to address limitations in selectivity and reactivity in the present literature. The research described herein will be comprised of three aims: (1) developing approaches for improving quantum yield of excited-state Ni bond homolysis processes, (2) explore and extend the scope of organic radical centers accessed by photoelimination, and (3) employing photoelimination as fundamental step in Ni catalysis. All three aspects will be explored concurrently and together represent an exciting new direction in the field of first-row transition metal catalysis.