Nickel-Catalyzed Direct Synthesis of Quinoxalines from 2-Nitroanilines and Vicinal Diols: Identifying Nature of the Active Catalyst

Abstract

The inexpensive and simple NiBr2/1,10-phenanthroline system-catalyzed synthesis of a series of quinoxalines from both 2-nitroanilines and 1,2-diamines is demonstrated. The reusability test for this system was performed up to the seventh cycle, which afforded good yields of the desired product without losing its reactivity significantly. Notably, during the catalytic reaction, the formation of the heterogeneous Ni-particle was observed, which was characterized by PXRD, XPS, and TEM techniques.

Borrowing Hydrogen and Acceptorless Dehydrogenative Coupling in the Multicomponent Synthesis of N‐Heterocycles: A Comparison between Base and Noble Metal Catalysis

“…[35] Some examples for the acceptorless dehydrogenative coupling of 2-phenylenediamines and vicinal diols were reported with abundant metals as well. [17,18,20,28,36,38] The NNNcobalt(II) pincer complex Co-3 was found to be active in the formation of quinoxalines 11 starting from vicinal diols and 2phenylenediamines (Scheme 18a). [17] A large excess of diol (5 equivalents) was required in order to obtain the quinoxaline 11 in satisfying yield.…”

“…[37] A phenanthroline nickel catalyst system that was recently reported for its high reactivity in the synthesis of pyridines 8 (Scheme 15) and pyrroles 33 (see Section 2.12) was applied to these two reactions as well (Scheme 18b). [38] Particular noteworthy is that heterogeneous Ni-particles were detected during the catalytic reaction and were characterized by PXRD, XPS, and TEM techniques. The air-stable, phosphinefree nickel complex Ni-3, which was reported for the formation of quinolines 1 under aerobic conditions (Scheme 6), was shown to be active to promote the reaction of diols and diamines to quinoxalines 11 as well (Scheme 18c).…”

Recent Progress in the Synthesis of Heterocycles through Base Metal‐Catalyzed Acceptorless Dehydrogenative and Borrowing Hydrogen Approach

“…Initially, the terminal alcohol group of the 1,2-diol is dehydrogenated to form (36). Condensation of the amine group of 1,2-diaminobenzene (8) with the carbonyl moiety of the formed (36) generates (86). This upon proton shift and successive tautomerization generates (88) (Figure 22).…”

“…The scope of the reaction has been extended via implementation of various cyclic and acyclic 1,2‐diols ( 34 ) for diverse quinaxolines ( 85 ) synthesis with moderate isolated yield (23 examples) in accordance with successful application of gram‐scale synthesis. In 2020 of Kundu and co‐workers [86] introduced the NiBr 2 /Phenanthroline ( L1 ) catalytic system for the coupling of 1,2‐diaminobenzene ( 8 ) (or 2‐nitroaniline ( 18 ) with various vicinal diols ( 34 ) (Scheme 39). The catalytic system involves the use of NiBr 2 /Phenanthroline, L1 (3‐5 mol%) in the presence of CsOH.H 2 O (0.4‐0.75 equiv.)…”

Cyclocondensation of o‐Phenylenediamines with 2‐Oxo‐ethanimidothioates: A Novel Synthesis of 2‐Amino‐3‐(het)aryl‐quinoxalines

“…The conventional method for the synthesis of quinoxalines involves the condensation of aromatic o-phenylene diamine with 1,2 diketones, [12] primary amines, [13] benzyl ketones, [14] aldehydes [15] and ynones. [16] The other important methods are Ni-catalysed condensation of 2-nitro anilines with vicinal diols [17] and Cu-catalysed cycloamination of N-aryl ketimines with azide. [18] Among the quinoxalines class, amino derivatives stands a top.…”