Efficient method for the preparation of pinacols derived from aromatic and aliphatic ketones by using low-valent titanium reagents in dichloromethane-pivalonitrile
aldehydes and ketones, including unsymmetrical aliphatic ketones, proceeded smoothly to give the corresponding pinacols in good to high yields under mild conditions by using combination of titanium(II) chloride and zinc or titanium(IV) chloride and zinc in dichloromethane-pivalonitrile. Meso-selective formation of the coupling products was observed in the cases of some aliphatic ketones. The diastereoselectivities
Iron-catalyzed Pinacol Coupling of Aryl Ketones with a Phenyltitanium Reagent: A New Type of Catalytic Reaction
作者:Tamio Hayashi、Keigo Sasaki
DOI:10.1246/cl.2011.492
日期:2011.5.5
A reaction of aryl ketones with phenyltitanium triisopropoxide ([PhTi(Oi-Pr)3]) in the presence of [Fe(acac)3] as a catalyst (1 mol %) gave the corresponding pinacols in high yields. The catalytic cycle of this process involves an iron-catalyzed disproportionation of [PhTi(Oi-Pr)3] into biphenyl and a low-valent titanium species.
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。
Electrochemical pinacol coupling of aromatic carbonyl compounds in a [BMIM][BF4]–H2O mixture
aromatic carbonylcompounds were carried out using an 80% [BMIM][BF4]–H2O mixture as the electrolytic medium. The corresponding diols were obtained in good to excellent yields with moderate diastereoselectivity. The stereoselectivity can be explained using the strongly-bound ion-pairs formed between the imidazolium cation and the radical anions of the carbonylcompounds. The ionicliquid replaces both
Mechanism of the Grignard reaction. Reaction of benzil
作者:Kazuhiro. Maruyama、Toshimasa. Katagiri
DOI:10.1021/ja00280a025
日期:1986.10
On demontre que 2 especes paramagnetiques stables participent comme veritables intermediaires de reaction et que la reaction de Grignard a lieu par etapes (transfert initial d'electrons au benzile→transfert de radical alkyl (ou aryl) au radical anionique→second transfert d'electron→second transfert de radical alkyl (ou aryl)) pour conduire au pinacol ou au produit final
On Demontre que 2 esspeces paramagnetiques stables participent comme veritables intermediaires de reaction et que la reaction de Grignard a lieu par etapes (transfert initial d'electrons au benzile→transfert de自由基烷基(ou aryl) au自由基阴离子→second transfert d'electron→第二次转移去自由基烷基(ou 芳基))倒入 conduire au pinacol ou au produit final