radical, 2) cleavage of the formyl C‒H bond of the aldehyde substrates by a thiyl radical acting as a hydrogen atom transfer catalyst to generate acyl radicals, 3) Minisci-type addition of the resulting acyl radicals to N-heteroaromatics, and 4) a spin-center shift, photoredox-catalyzed single-electron reduction, and protonation to produce secondaryalcohol products. This metal-free hybrid catalysis proceeded
promote the cleavage of stable C–H bonds, such as formyl, α-hydroxy, and benzylic C–H bonds, through a hydrogen atom transfer (HAT) process without the use of exogenous photosensitizers. An electronically tuned thiophosphoric acid, 7,7’-OMe-TPA, was assembled with substrate or co-catalyst N-heteroaromatics through hydrogen bonding and π–π interactions to form electron donor–acceptor (EDA) complexes. Photoirradiation
我们开发了有机催化剂系统,通过氢原子转移 (HAT) 过程促进稳定的 C-H 键断裂,例如甲酰基、α-羟基和苄基 C-H 键,而无需使用外源光敏剂。电子调谐的硫代磷酸 7,7'-OMe-TPA通过氢键和 π-π 相互作用与底物或助催化剂N-杂芳烃组装,形成电子供体 - 受体 (EDA) 复合物。EDA 复合物的光辐照诱导逐步、连续的单电子转移 (SET) 过程以产生 HAT 活性硫自由基。第一个 SET 是从 7,7'-OMe-TPA 的富电子萘基到质子化的N-杂芳烃和从 7,7'-OMe-TPA 的硫代磷酸部分到所得萘基自由基阳离子的第二个质子偶联 SET (PCET)。光谱研究和理论计算表征了由短寿命中间体介导的逐步 SET 过程。该有机催化 HAT 系统应用于四种不同的碳氢 (C-H) 官能化反应、N-杂芳烃的羟烷基化和烷基化、醇的无受体脱氢和亚胺的苄基化,具有高官能团耐受性。
Cobalt‐Promoted Transfer Hydrogenation of Azaaryl Ketones by Using Formate as the Hydrogen Source
A cobalt-catalyzed transferhydrogenation of azaaryl ketones using formate as hydrogen source was developed and a possible reaction mechanism is proposed.
A method for chemoselective reduction of 2-pyridyl ketones and related N-heteroaryl compounds catalyzed by cobalt stearate using DMF as a hydride source is developed. The ketone substrate is activated by chelation with cobalt, which makes the present method highly chemoselective. A possible reaction mechanism is proposed on the basis of control experiments.