5653-09-8Relevant articles and documents
Nickel-Catalyzed Reductive Acylation of Carboxylic Acids with Alkyl Halides and N-Hydroxyphthalimide Esters Enabled by Electrochemical Process
Zhou, Xiao,Guo, Lin,Zhang, Haoxiang,Xia, Raymond Yang,Yang, Chao,Xia, Wujiong
, p. 1526 - 1531 (2022/03/31)
A sustainable Ni-catalyzed reductive acylation reaction of carboxylic acids via an electrochemical pathway is presented, affording a variety of ketones as major products. The reaction proceeds at ambient temperature using unactivated alkyl halides and N-hydroxyphthalimide (NHP) esters as coupling partners, which exhibits several synthetic advantages, including mild conditions and convenience of amplification (58% yield for 6 mmol scale reaction). (Figure presented.).
A General Organocatalytic System for Electron Donor-Acceptor Complex Photoactivation and Its Use in Radical Processes
De Pedro Beato, Eduardo,Melchiorre, Paolo,Spinnato, Davide,Zhou, Wei
supporting information, p. 12304 - 12314 (2021/08/20)
We report herein a modular class of organic catalysts that, acting as donors, can readily form photoactive electron donor-acceptor (EDA) complexes with a variety of radical precursors. Excitation with visible light generates open-shell intermediates under mild conditions, including nonstabilized carbon radicals and nitrogen-centered radicals. The modular nature of the commercially available xanthogenate and dithiocarbamate anion organocatalysts offers a versatile EDA complex catalytic platform for developing mechanistically distinct radical reactions, encompassing redox-neutral and net-reductive processes. Mechanistic investigations, by means of quantum yield determination, established that a closed catalytic cycle is operational for all of the developed radical processes, highlighting the ability of the organic catalysts to turn over and iteratively drive every catalytic cycle. We also demonstrate how the catalysts' stability and the method's high functional group tolerance could be advantageous for the direct radical functionalization of abundant functional groups, including aliphatic carboxylic acids and amines, and for applications in the late-stage elaboration of biorelevant compounds and enantioselective radical catalysis.
Palladium-Catalyzed Dual Ligand-Enabled Alkylation of Silyl Enol Ether and Enamide under Irradiation: Scope, Mechanism, and Theoretical Elucidation of Hybrid Alkyl Pd(I)-Radical Species
Zhao, Bin,Shang, Rui,Wang, Guang-Zu,Wang, Shaohong,Chen, Hui,Fu, Yao
, p. 1334 - 1343 (2020/02/04)
We report herein that a palladium catalyst in combination with a dual phosphine ligand system catalyzes alkylation of silyl enol ether and enamide with a broad scope of tertiary, secondary, and primary alkyl bromides under mild irradiation conditions by blue light-emitting diodes. The reactions effectively deliver α-alkylated ketones and α-alkylated N-acyl ketimines, and it is difficult to prepare the latter by other methods in a stereoselective manner. The α-alkylated N-acyl ketimine products can be further subjected to chiral phosphoric acid-catalyzed asymmetric reduction with Hantzsch ester to deliver chiral N-acyl-protected α-arylated aliphatic amines in high enantioselectivity up to 99% ee, thus providing a method for facile synthesis of chiral α-arylated aliphatic amines, which are of importance in medicinal chemistry research. The N-acetyl ketimine product also reacted smoothly with various types of Grignard reagents to afford sterically bulky N-acetyl α-tertiary amines in high yields. Theoretical studies in combination with experimental investigation provide understanding of the reaction mechanism with respect to the dual ligand effect and the irradiation effect in the catalytic cycle. The reaction is suggested to proceed via a hybrid alkyl Pd(I)-radical species generated by inner-sphere electron transfer of phosphine-coordinated Pd(0) species with alkyl bromide. This intriguing hybrid alkyl Pd(I)-radical species is elucidated by theoretical calculation to be a triplet species coordinated by three phosphine atoms with a distorted tetrahedral geometry, and spin prohibition rather than metal-to-ligand charge transfer contributes to the kinetic stability of the hybrid alkyl Pd(I)-radical species to impede alkyl recombination to generate Pd(II) alkyl intermediate.
