Ytterbium pentafluorobenzoate as a novel fluorous Lewis acid catalyst in the synthesis of 2,4-disubstituted quinolines

Tang, Jun; Wang, Limin; Mao, Dan; Wang, Wenbo; Zhang, Liang; Wu, Shengying; Xie, Yongshu

doi:10.1016/j.tet.2011.09.004

Cited by 53 publications

(29 citation statements)

References 29 publications

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“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 21 Three very similar MCR procedures involving aniline, aldehydes and phenylacetylene, at temperatures between 70ºC and 120ºC have been disclosed. Syntheses catalysed by HClO4modified Montmorillonite, 94 Fe(OTf)3 95 or Yb(Pfb)3 96 were performed with good yields and with excellent recyclability rates. Yet, a thorough synthesis of different substituents was only performed in Fe(OTf)3, revealing good yields.…”

Section: Scheme 14mentioning

confidence: 99%

Synthesis of Quinolines: A Green Perspective

Batista

Pinto

Silva

2016

ACS Sustainable Chem. Eng.

115

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The quinoline scaffold is present in a vast number of natural compounds and pharmacologically active substances, comprising a significant segment of the pharmaceutical market. The classical methods for the synthesis of this heterocyclic skeleton require the use of expensive starting materials and high temperature conditions. Chemists play a fundamental role in the construction of a sustainable future through the pursuit of greener chemical processes. As so, the development of new synthetic methods using more efficient energy sources and less hazardous solvents as well as renewable and eco-friendly catalysts to attain the quinoline scaffold can provide significant environmental and economic advantages. This review unveils green methods used in the synthesis of quinolones. Important green metrics are calculated for each proposed method and the statistical analysis allowed us to propose the best approaches for further investigation. The applied research is eventually unveiling the full potential of Friedländer and/or multicomponent reactions, to improve atom economy. The quinoline structural motif is readily available through a number of classical synthetic routes and from commercially available reagents. The Friedländer synthetic method (A) from ortho-aminoacetophenones (10) and the Skraup (B), Combes (D) and Doebner-Miller (F) syntheses from anilines (11), as well as its adaptations, are good examples. Moreover, the Conrad-Limpach (C), Gould-Jacobs (E) and Camps (G) routes for the synthesis of quinolones are widely used methods (Scheme 1). Still, all classical methods have similar disadvantages, requiring highly acidic and/or oxidizing media, high temperatures and long reaction times.Moreover, most of these synthetic routes present selectivity problems with meta-substituted substrates and its versatility is limited by the reactivity of the methylenic carbon involved in the aldol reaction. 19 Although efficient and versatile, classical routes towards the synthesis of quinolines present serious environmental concerns as most synthetic routes use great excess of a reagents and produce a significant amount of toxic waste.

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Section: Scheme 14mentioning

confidence: 99%

Synthesis of Quinolines: A Green Perspective

Batista

Pinto

Silva

2016

ACS Sustainable Chem. Eng.

115

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“…[59] The synthesis of the catalyst was an arduous technique that required the reaction of rare earth metals with pentafluorobenzoic acid and water. The Ytterbium catalyst (2 mol%) was used to promote the reaction of various aldehydes 31, amines 32 and alkynes 33 under solvent-free conditions for 12 hours to produce the desired substituted quinolines in good to excellent yields (69-96%) (Scheme 15).…”

Section: Miscellaneous-catalyzed Systems For a 3 -Couplingmentioning

confidence: 99%

“…The Ytterbium catalyst (2 mol%) was used to promote the reaction of various aldehydes 31, amines 32 and alkynes 33 under solvent-free conditions for 12 hours to produce the desired substituted quinolines in good to excellent yields (69-96%) (Scheme 15). [59] In addition, a catalyst recover and reuse study had to be applied, due to the cost of the expensive catalyst. [59] Drawbacks of this catalyst system are displayed in Table 6.…”

Section: Miscellaneous-catalyzed Systems For a 3 -Couplingmentioning

confidence: 99%

“…[59] In addition, a catalyst recover and reuse study had to be applied, due to the cost of the expensive catalyst. [59] Drawbacks of this catalyst system are displayed in Table 6.…”

Section: Miscellaneous-catalyzed Systems For a 3 -Couplingmentioning

confidence: 99%

“…FeCl3 was chosen as the iron catalyst due to its; high abundance, low cost and environmentally friendly properties [86] , however, it has been argued that the catalyst loading of FeCl3 used was not satisfactory. [59] From literature, FeCl3 systems had large catalyst loading and required long reaction times and the use of a solvent, [55], [56] we decided to modify this methodology and in order for this system to be viable we had to decrease the amount of FeCl3 to 1 mol% to determine if 2,4-disubstituted quinoline derivatives could still be synthesized in good to excellent yields. We envisaged that a low catalyst loading coupled with the inexpensive nature of FeCl3 will generate a powerful catalytic system as it is one of the core principles of Green Chemistry.…”

Section: Iron-based Systemmentioning

confidence: 99%

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