A Green Synthesis of Quinoxalines and 2,3-Dihydropyrazines

Delpivo, Camilla; Micheletti, Gabriele; Boga, Carla

doi:10.1055/s-0033-1338441

Cited by 28 publications

(3 citation statements)

References 26 publications

(26 reference statements)

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“…Spectroscopic data matched with those reported in the literature. 41 1 H NMR (CDCl 3 , 400 MHz): δ 7.93−7.91 (m, 2H), 7.54−7.52 (m, 2H), 2.95−2.89 (m, 4H), 1.34−1.30 (m, 6H); 13 C{ 1 H} NMR (CDCl 3 , 100 MHz): δ 157.0, 140.9, 128.9, 128.4, 28.2, 12.3 ppm.…”

Section: ■ Experimental Sectionsupporting

confidence: 83%

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Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions

2020

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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.

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Section: ■ Experimental Sectionsupporting

confidence: 83%

“…White solid (141 mg, 76%); eluent combination: hexane/ethyl acetate (10:1). Spectroscopic data matched with those reported in the literature …”

Section: Methodsmentioning

confidence: 99%

Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions

2020

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“…These molecules possess high reactivity due to the presence of the two, adjacent electron-deficient carbonyl groups, hence, they are used as starting materials or intermediates in modern organic synthesis and organocatalytic transformations. [49][50][51] In addition, they are utilized as key building blocks in the preparation of biologically active compounds such as pyrazines, [52][53][54][55] dihydropyrazines, 56 quinoxalines, [57][58][59][60] oxazoles, 61 and imidazoles (vide infra). 62 Furthermore, 1,2-diketones have displayed unique applications as photo-initiators and photosensitive agents.…”

Section: Allylation Of Alkenesmentioning

confidence: 99%

One-pot, multicomponent oxidative synthesis of 2,4,5-trisubstituted imidazoles from internal alkenes using an I2/DMSO system.

Majola

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Imidazoles are vital heterocyclic compounds usually incorporated in natural products such as biotin, vitamin B12, histamine, and histidine. 2,4,5-trisubstituted imidazoles, in particular, possess versatile biological and pharmaceutical activities such as antidiabetic, antimalarial, and analgesic properties. A traditional procedure for the synthesis of these elegant compounds involves the cyclocondensation reaction between a 1,2-diketone, an aldehyde, and ammonia in the presence of an acid or metal catalyst. However, this methodology suffers from various shortcomings such as the use of acid or metal catalysts, tedious work-up procedures, use of toxic reagents, and substrate scope limitations. Hence, the development of new methods to synthesize 2,4,5-trisubstituted imidazoles is of vital importance. This study describes the preparation of 2,4,5-trisubstituted imidazoles from alkenes using an environmentally benign iodine/DMSO system. This novel methodology was applied to a broad substrate scope such as substituted benzaldehydes, heterocyclic aldehydes, bulkier aldehydes, and substituted stilbenes, and afforded the target compounds in moderate to high yields under mild reaction conditions. Preliminary mechanistic studies revealed that 1,2-diketone is a key intermediate and that the mechanism is not radical-mediated. It also revealed that the oxygen source is DMSO and that the coupling step is catalyzed by iodine coordination and hydrogen bonding from the solvent. Based on the results obtained from the preliminary mechanistic investigations, a reasonable mechanism is proposed.

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Multicomponent and One‐pot Syntheses of Quinoxalines

Biesen

Müller

2021

Adv Synth Catal

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Quinoxalines represent bicyclic nitrogen‐containing heterocycles with a wide array of applications. They exhibit a multitude of biological activities relevant in medicinal chemistry as well as a plethora of luminescence properties. Quinoxaline syntheses exploit the whole raft of multicomponent syntheses from domino to sequential or consecutive reactions, harvesting well‐known synthetic concepts and reactions, such as Ugi‐reactions, but also leading to the development of novel reactions and sequences. Diversity‐oriented synthesis and transition metal catalyzed multicomponent reactions open efficient pathways to quinoxalines and quinoxaline‐containing moieties in a one‐pot fashion. This review outlines the underlying reaction‐based principles of multicomponent syntheses of quinoxalines and summarizes recent developments quinoxaline‐directed MCRs, illustrating their scopes.

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A Green Synthesis of Quinoxalines and 2,3-Dihydropyrazines

Cited by 28 publications

References 26 publications

Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions

Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions

One-pot, multicomponent oxidative synthesis of 2,4,5-trisubstituted imidazoles from internal alkenes using an I2/DMSO system.

Multicomponent and One‐pot Syntheses of Quinoxalines

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