Base-Free Synthesis of Furfurylamines from Biomass
Total Page：16
File Type：pdf, Size：1020Kb
catalysts Communication CommunicationBase-Free Synthesis of Furfurylamines from Biomass Furans Base-Free Synthesis of Furfurylamines from Biomass Furans Using Ru Pincer Complexes Using Ru Pincer Complexes Danielle Lobo Justo Pinheiro and Martin Nielsen * Danielle Lobo Justo Pinheiro and Martin Nielsen * Department of Chemistry, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark; [email protected] of Chemistry, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark; [email protected] ** Correspondence:Correspondence:[email protected]; [email protected];Tel.: Tel.:+45-24651045 +45-24651045 Abstract: WeWe reportreport thethe firstfirst exampleexample ofof employingemploying homogeneoushomogeneous organometal-catalyzedorganometal-catalyzed transfertransfer hydrogenation for the selectiveselective reductivereductive aminationamination ofof furfuralsfurfurals toto furfurylamines.furfurylamines. An efficient,efficient, chemoselective, andand base-freebase-free methodmethod isis describeddescribed usingusing Ru-MACHO-BHRu-MACHO-BH asas catalystcatalyst andand iiPrOHPrOH asas H donor. The method toleratestolerates aa rangerange ofof substituentssubstituents affordingaffording moderatemoderate toto excellentexcellent yields.yields. Keywords: transfer hydrogenation; furfurals;furfurals; furfurylamine;furfurylamine; reductivereductive amination;amination; Ru-MACHORu-MACHO 1. Introduction The development of sustainable techniques to transform biomass into useful com- pounds is one of of the the biggest biggest challenges challenges of of mo moderndern chemistry chemistry [1]. [1 ].The The introduction introduction of ni- of nitrogentrogen in in biomass-derived biomass-derived compounds compounds adds adds va valuelue and and expands expands their their industry industry applicabil- applicabil- ityity [[2].2]. FurfuralsFurfurals are aldehydesaldehydes derivedderived fromfrom biomass and are identifiedidentified asas oneone ofof thethe keykey Citation:Citation: Pinheiro,Pinheiro, D. D.L.J.; L. J.; Nielsen, Nielsen, M. chemicalschemicals producedproduced byby thethe lignocellulosiclignocellulosic biorefineries.biorefineries. Around 280 kTon areare producedproduced Base-FreeM. Base-Free Synthesis Synthesis of of globallyglobally per year year [3]. [3]. Furfurylamines Furfurylamines (amines (amines derived derived from from furfurals) furfurals) present present diverse diverse ap- Furfurylamines from Biomass Furfurylamines from Biomass Furans applicationsplications in inthe the industry, industry, including including the the pr preparationeparation of of pharmaceutical pharmaceutical compounds suchsuch UsingFurans Ru Using Pincer Ru Complexes. Pincer Complexes.Catalysts asas Furesomide,Furesomide, Furtrethonium,Furtrethonium, anan anti-hepatitis-B,anti-hepatitis-B, and BarmastineBarmastine (Figure1 1),), asas well well as as 2021Catalysts, 11, 558.2021 ,https://doi.org/ 11, x. polymers,polymers, antisepticantiseptic agents,agents, agrochemicals,agrochemicals, pesticides,pesticides, andand syntheticsynthetic resinsresins [1[1,2,4].,2,4]. 10.3390/catal11050558https://doi.org/10.3390/xxxxx AcademicAcademic Editors:Editors: Raffaele Cuccini- N Raffaeleello, Daniele Cucciniello, Cespi and Daniele Tommaso Cespi N O Cl HN N andTabanelli Tommaso Tabanelli O O HO N O HN S O O I N NH 2 O Received:Received: 3030 MarchMarch 20212021 O N HN N N Accepted:Accepted: 2626 AprilApril 20212021 OH Published: 28 April 2021 Published: 27 April 2021 Furesomide Furtrethonium Anti-Hepatitis - B Barmastine Publisher’sPublisher’s Note:Note:MDPI MDPI stays stays neutral neu- FigureFigure 1.1. Pharmaceutical compoundscompounds containingcontaining furfurylamines.furfurylamines. withtral regardwith regard to jurisdictional to jurisdictional claims in publishedclaims in published maps and maps institutional and institu- affil- TheThe synthesissynthesis ofof furfurylaminesfurfurylamines from furfurals by reductive amination has been in- iations.tional affiliations. vestigatedvestigated usingusing diversediverse reducingreducing agentsagents andand catalysts.catalysts. Studies involving hydrogen gas, silanes,silanes, borohydrides,borohydrides, andand formic acid as reductantsreductants have been reported in the literature. HydrogenHydrogen gasgas as as reductant reductant is is an an interesting interesting green green tool; tool; however, however, the methodthe method needs needs to oper- to ateoperate under under pressure pressure of a highly of a highly flammable flammabl gas,e increasing gas, increasing the operating the operating cost. Nevertheless, cost. Never- Copyright: © 2021 by the authors. there are many examples in the literature using H as reductant for reductive amination Copyright: © 2021 by the authors. theless, there are many examples in the literature using2 H2 as reductant for reductive ami- Submitted for possible open access Licensee MDPI, Basel, Switzerland. withnation noble with andnoble non-noble and non-noble metal metal catalysts catalyst suchs assuch Ru, as Au, Ru, Ir,Au, Pt, Ir, Ni, Pt, CoNi, andCo and Fe [Fe5– 11[5–]. publication under the terms and This article is an open access article Although11]. Although silane silane is obtained is obtained from from waste waste residues residues of the of silicon the silicon industry, industry, their use their is stilluse inis conditions of the Creative Commons distributed under the terms and stoichiometricstill in stoichiometric amounts, amounts, generating generating excessive excessive amounts amounts of waste of [ 12waste–14]. [12–14]. The use The of formic use of Attribution (CC BY) license conditions of the Creative Commons acidformic as Hacid donor as H for donor the reductive for the reductive amination amin of furfuralation of wasfurfural demonstrated was demonstrated as well. Cao as well. and (http://creativecommons.org/licenses Attribution (CC BY) license (https:// co-workers synthesized N-(furan-2-ylmethyl)aniline in 93% yield from nitrobenzene and /by/4.0/). ◦ creativecommons.org/licenses/by/ furfural using Au/TiO2-R as catalyst at 80 C for 4 h [15]. Smith Jr and co-workers also 4.0/). employed formic acid as H donor, but used formamide as N source [16]. To the best of our Catalysts 2021, 11, x. https://doi.org/10.3390/xxxxx www.mdpi.com/journal/catalysts Catalysts 2021, 11, 558. https://doi.org/10.3390/catal11050558 https://www.mdpi.com/journal/catalysts Catalysts 2021, 11, x FOR PEER REVIEW 2 of 11 Cao and co-workers synthesized N-(furan-2-ylmethyl)aniline in 93% yield from nitroben- Catalysts 2021, 11, 558 zene and furfural using Au/TiO2-R as catalyst at 80 °C for 4 h [15]. Smith Jr and co-workers2 of 10 also employed formic acid as H donor, but used formamide as N source [16]. To the best of our knowledge, the only work involving an alcohol as H donor (iPrOH) for the synthe- sis of furfurylamines from furfural was reported by Yus [17]. In this work, the reaction knowledge,between furfural the only and work heptylamine involving using an alcohol 20 mol% as of H NiNPs donor at (iPrOH) 76 °C for for 48 the h afforded synthesis 30% of furfurylamines from furfural was reported by Yus [17]. In this work, the reaction between yield of the furfurylamine. ◦ furfuralOne and of heptylaminethe most powerful using 20and mol% robust of NiNPsmethods at 76for effectiveC for 48 hC–N afforded bond 30%formation yield of of theamines furfurylamine. is the reductive amination of carbonyl compounds. [4,18–30]. This transformation featuresOne ofcompelling the most powerfuladvantages, and such robust as methodssimple operating for effective setups, C–N mild bond reaction formation condi- of aminestions, direct is the use reductive of available amination substrates, of carbonyl and inexpensive compounds. reagents [4,18–30 [31].]. This The transformation reductive ami- features compelling advantages, such as simple operating setups, mild reaction conditions, nation using transfer hydrogenation for the synthesis of furfurylamines from furfurals is direct use of available substrates, and inexpensive reagents [31]. The reductive amination limited, even though this transformation as a synthetic tool is non-toxic, environmentally using transfer hydrogenation for the synthesis of furfurylamines from furfurals is limited, friendly, does not require flammable gasses, and employs a stable, easy to handle, and even though this transformation as a synthetic tool is non-toxic, environmentally friendly, inexpensive source of hydrogen [4,32–37]. However, transfer hydrogenation catalysts typ- does not require flammable gasses, and employs a stable, easy to handle, and inexpensive ically require strong bases to be active, which can be detrimental for substrates that are source of hydrogen [4,32–37]. However, transfer hydrogenation catalysts typically require base-sensitive [38]. Therefore, studies applying base-free conditions must be developed to strong bases to be active, which can be detrimental for substrates that are base-sensitive [38]. avoid this drawback. Therefore, studies applying base-free conditions must be developed to avoid this drawback. The use of homogenous metal catalysis has demonstrated great reactivity for transfer The use of homogenous metal catalysis has demonstrated great reactivity for trans- hydrogenation of carbonyl compounds and has been proven to hold many advantages fer hydrogenation of carbonyl compounds and has been proven to hold many advan- [38–41]. In 2018, De Vries reported a base-free transfer hydrogenation of α,β-unsaturated tages [38–41]. In 2018, De Vries reported