Light-enabled metal-free pinacol coupling by hydrazine
作者:Zihang Qiu、Hanh D. M. Pham、Jianbin Li、Chen-Chen Li、Durbis J. Castillo-Pazos、Rustam Z. Khaliullin、Chao-Jun Li
DOI:10.1039/c9sc03737c
日期:——
Efficientcarbon–carbonbondformation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C–C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability
高效的碳-碳键形成在现代有机合成化学中非常重要。一个多世纪前发现的频哪醇偶联仍然是一步构建 C-C 键的最有效偶联反应之一。然而,传统频哪醇偶联通常需要过量化学计量的活性金属作为还原剂,从而导致长期存在的金属废料问题和可持续性问题。一个巨大的科学挑战是设计一种无金属的频哪醇偶联反应方法。在这里,我们描述了一种光驱动频哪醇耦合协议,不使用任何金属,但使用 N 2 H 4,用作清洁的非金属氢原子转移 (HAT) 还原剂。在这种转化中,只有无痕无毒的N 2和H 2气体作为副产物产生,具有相对广泛的芳香酮范围和良好的官能团耐受性。对该机制的实验和计算研究表明,这种新颖的频哪醇偶联反应是通过光激发酮和 N 2 H 4之间的 HAT 过程进行的,而不是金属还原剂的常见单电子转移 (SET) 过程。
Reductive Coupling of Carbonyl Compounds to Pinacols with Zinc in THF-Saturated Aqueous Ammonium Chloride
作者:Rahim Hekmatshoar、Issa Yavari、Yahya S. Beheshtiha、Majid M. Heravi
DOI:10.1007/s007060170083
日期:2001.6
In the presence of metallic zinc, aldehydes and ketones experience reductive coupling in tetrahydrofuran-saturated aqueousammoniumchloride (5:3) to afford the corresponding pinacols in moderate to high yields.
requires sensitive reducing metal, the current method employs a stable diboron reagent and pyridine Lewis base catalyst for the generation of a ketyl radical. The newly developed process is operationally simple, and the desired diols are produced with excellent efficiency in up to 99% yield within 1 hour. The superior reactivity of diaryl ketone was observed over monoaryl carbonyl compounds and analyzed
Hydrodimerisation electrochimique de cetones aromatiques encombrees en milieu aprotique et en presence de chlorure de chrome
作者:F. Fournier、J. Berthelot、Y.L. Pascal
DOI:10.1016/s0040-4020(01)91180-9
日期:1984.1
The electrochemical reduction of hindered aromatic ketones which are difficult to reduce alone, can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in presence of Cr(III) chloride, at the reduction potential or the Cr(II)/Cr(0) system, but at a less negative potential than that of the ketone itself. There is selective hydrodimerisation into an α-glycol, with total lack of polymerisation
microwave pulse much later than the laser pulse or off-resonant to the radical pair had no effect on the product yield. On the other hand, a reverse effect of the microwave pulse was observed on the yield of the cage product, XOH−XH. The yields as a function of the magneticfield correspond to the ESR spectrum of the intermediate radical pair.
x吨(XH 2)对黄酮(XO; X = C 13 H 8 O)的光化学还原十二烷基硫酸钠胶束中的)是通过磁场中的共振微波脉冲来控制的。通过高效液相色谱法测量产物收率。在大约335 mT的磁场下,在激光脉冲持续6.0μs之后立即施加的微波脉冲(9380 MHz; 1.0 kW)将逸出产物XOH-XOH和XH-XH减少到不到无逸出产物的三分之一。微波脉冲。微波脉冲比激光脉冲晚得多或与自由基对不共振,对产物收率没有影响。另一方面,观察到微波脉冲对笼形产品XOH-XH的产率产生相反的影响。作为磁场的函数的产率对应于中间自由基对的ESR谱。