6344-72-5Relevant articles and documents
Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions
Bains, Amreen K.,Singh, Vikramjeet,Adhikari, Debashis
, p. 14971 - 14979 (2020/11/30)
Dehydrogenative coupling-based reactions have emerged as an efficient route toward the synthesis of a plethora of heterocyclic rings. Herein, we report an efficacious, nickel-catalyzed synthesis of two important heterocycles such as quinoline and quinoxaline. The catalyst is molecularly defined, is phosphine-free, and can operate at a mild reaction temperature of 80 °C. Both the heterocycles can be easily assembled via double dehydrogenative coupling, starting from 2-aminobenzyl alcohol/1-phenylethanol and diamine/diol, respectively, in a shorter span of reaction time. This environmentally benign synthetic protocol employing an inexpensive catalyst can rival many other transition-metal systems that have been developed for the fabrication of two putative heterocycles. Mechanistically, the dehydrogenation of secondary alcohol follows clean pseudo-first-order kinetics and exhibits a sizable kinetic isotope effect. Intriguingly, this catalyst provides an example of storing the trapped hydrogen in the ligand backbone, avoiding metal-hydride formation. Easy regeneration of the oxidized form of the catalyst under aerobic/O2 oxidation makes this protocol eco-friendly and easy to handle.
Nickel/Photoredox-Catalyzed Methylation of (Hetero)aryl Chlorides Using Trimethyl Orthoformate as a Methyl Radical Source
Kariofillis, Stavros K.,Shields, Benjamin J.,Tekle-Smith, Makeda A.,Zacuto, Michael J.,Doyle, Abigail G.
supporting information, p. 7683 - 7689 (2020/04/22)
Methylation of organohalides represents a valuable transformation, but typically requires harsh reaction conditions or reagents. We report a radical approach for the methylation of (hetero)aryl chlorides using nickel/photoredox catalysis wherein trimethyl orthoformate, a common laboratory solvent, serves as a methyl source. This method permits methylation of (hetero)aryl chlorides and acyl chlorides at an early and late stage with broad functional group compatibility. Mechanistic investigations indicate that trimethyl orthoformate serves as a source of methyl radical via β-scission from a tertiary radical generated upon chlorine-mediated hydrogen atom transfer.
Iron-catalyzed Minisci acylation of N-heteroarenes with α-keto acids
Wang, Xiu-Zhi,Zeng, Cheng-Chu
supporting information, p. 1425 - 1430 (2019/02/01)
An efficient and mild protocol has been developed for the Minisci acylation reactions of nitrogen-containing heteroarenes with α-keto acids. Distinct from the conventional Minisci acylation conditions, the chemistry was performed using non-noble metal Fe(II), instead of expensive Ag(I) salt, as catalyst. A wide range of substrates, including aliphatic or aromatic α-keto acids, as well as various N-heteroarenes, proved to be compatible with the protocol. Scale-up experiment also demonstrates the practicality of the approach.
