Dr. Qifeng Yang finished his postdoc project proposal

Dr. Qifeng Yang finished his postdoc project proposal

June 21, 2021

Dr. Qifeng Yang finished the postdoc project proposal. He is currently working on heterogeneous electrochemical oxidation reactions. We are looking forward to the new electrosynthesis methods he is going to develop in the near future. And Thank Prof. Lian and Prof. Bao for attending the proposal meeting and giving constructive suggestions for the project.

Photo of the project proposal.
“清华大学化学工程联合国家重点实验室”邀请莫一鸣做学术报告

“清华大学化学工程联合国家重点实验室”邀请莫一鸣做学术报告

报告题目:流动电化学在有机合成领域的应用

报告摘要:电化学有机合成旨在利用电极所提供的氧化或者还原能力,活化原料分子形成活性中间体从而获得最终的产物。该方法无需额外提供氧化剂或者还原剂,从而显著提高了有机合成的原子利用效率、环保性与安全性,近些年在学术界逐渐获得广泛关注。本报告从电化学合成的反应机理出发,利用流动化学与微流控的反应器设计,精准控制反应活性中间体,实现高效率、高选择性的反应。报告主要包括:(1)针对反应动力学慢、电催化剂易分解、气-液两相的电化学合成体系,基于电化学分析揭示的电催化剂分解机理与反应动力学,构建了一套循环回流多相电化学反应装置,成功实现N-hydroxyphthalimide催化的卞位C–H氧化反应在流动体系下的高效、安全转化;(2)常规电化学反应主要依赖单电极反应,另一电极则用于平衡电子、产生副产物,通过化学反应机理的设计,在阴极与阳极同时产生活性中间体,同时利用微流控精准控制活性中间体的寿命,实现多种双电极的交叉偶联反应,为电化学合成设计提供了全新的思路;(3)针对发现与优化电化学反应需要大量人力物力的挑战,构建了一套全自动无人电化学优化平台,实现微纳摩尔量级的快速反应筛选。

Science:微流体电化学合成 (Microfluidic redox-neutral electrochemistry)

Science:微流体电化学合成 (Microfluidic redox-neutral electrochemistry)

在过去的几十多年里,可见光光催化剂在单电子转移(SET)的氧化还原中性反应(single-electron transfer redox-neutral reactions)上的巨大成功,同时也为合成化学家提供了强大的工具来制备那些传统方法难以合成的化合物。然而,这些光催化剂大多是贵金属络合物或复杂的有机染料,因此存在成本较高、氧化还原电势调节比较有限、与强亲核试剂、亲电试剂或自由基中间体不兼容以及在产物纯化过程中除去过渡金属比较困难等限制性。相比之下,电化学合成是一个新兴的氧化还原平台,优势在于环境友好、经济实惠、便于放大以及适用于多种转化。

利用微流控的氧化还原中性电化学(μRN-eChem)平台成功在两个电极产生活性中间体并发生想要的单电子自由基-自由基交叉偶联反应(SET radical-radical cross-coupling reactions)、Minisci反应和镍催化的C(sp2)-O交叉偶联反应,克服了之前光化学激发的单电子转移氧化还原反应的不足。其中的关键在于——正负电极之间极小的距离 25 μm。

Over the past decade, pioneering developments of visible-light photocatalysis in organic synthesis have enabled previously inaccessible redox-neutral reactions that proceed through single-electron transfer (SET) processes. Nonetheless, the use of photocatalysts, mostly precious metal complexes or sophisticated organic dyes (4), could have practical limitations, such as the non-trivial tuning of redox potentials, high cost of transition-metal photocatalysts at scale, incompatibility of photocatalysts with strong nucleophiles, electrophiles, or radical intermediates, and challenging removal of transition metals during purification of the products. Electrosynthesis, on the other hand, is an emerging redox platform accessing environmentally benign, cost-effective, scalable, and unique transformations powered by inexpensive electricity.

This work aims at unleashing the capability of microfluidic electrochemistry, and successfully developed a microfluidic redox-neutral electrochemical platform (µRN-eChem) to overcome the challenges of photochemistry-inspired SET redox-neutral reactions that involve reactive intermediates generated from both electrodes. Reactive intermediates, including radicals, generated from two different electrodes can rapidly diffuse through an extremely thin gap (25 µm) between cathode and anode forging new bond formations. A variety of cross-coupling reactions have been demonstrated, including radical-radical cross-coupling, Minisci-type reactions, and nickel-catalyzed C(sp2)–O cross-coupling.