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Article

Gold(III) Chloride-Mediated Transformation of Furfural to the trans-N,N-4,5-Diaminocyclopent-2-enones in the Presence of Anilines

by
Marina A. Tzani
and
Ioannis N. Lykakis
*
Department of Chemistry, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece
*
Author to whom correspondence should be addressed.
Chemistry 2023, 5(1), 393-405; https://doi.org/10.3390/chemistry5010029
Submission received: 7 February 2023 / Revised: 22 February 2023 / Accepted: 25 February 2023 / Published: 27 February 2023
(This article belongs to the Special Issue Heterogeneous Catalysis — A Themed Issue in Honor of Prof. Dr. Avelino Corma)
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Abstract

:
We investigated the efficient approach of a series of trans-N,N-4,5-substituted-diaminocyclopent-2-enones (trans-DACPs) from furfural and anilines mediated by Gold(III) chloride (HAuCl4). The present protocol required a low amount of the catalysts, 1.5 mol%, open air conditions, the absence of any additives, and short reaction times. The desired trans-DACPs were isolated in good to high yields. The protocol was also applied to secondary amines, leading to the corresponding 4,5-diamino-cyclopent-2-enones in good yields. To the best of our knowledge, this is the first gold-mediated paradigm as an efficient catalyst for the formation of the cyclopentenones core-bearing C-N bonds under mild reaction conditions.

Graphical Abstract

1. Introduction

Gold, either in a homogeneous [1,2,3,4,5,6,7] or heterogeneous medium [8,9,10,11,12,13,14,15,16], can act as a versatile catalyst for a broad range of chemical transformations. The field of homogeneous gold catalysis began to grow in the first decade of the 21st century, enabling the replacement of consolidated organic reactions with more simple, selective, and chemically sustainable alternatives. Gold catalysis is considered a hot topic in organic synthesis, with applications in the general topics of the total synthesis of complex molecular architectures [17,18] asymmetric synthesis [19,20], C-H activation reactions [21,22], and visible photoredox catalysis [23,24,25,26]. In the majority of homogeneous Au catalysts, Au exists in the +1 oxidation state and has a soft Lewis acidity. Unlike Au(I), Au(III) is a hard Lewis acid that preferentially binds to the lone pairs of heteroatoms such as O, N, and S [27,28,29,30]. The oxophilic Au(III) complexes may be employed to accelerate chemoselective reactions for which piphilic Au(I) complexes are less efficient [31,32]. Therefore, progression in Au(III) catalysis could expand the overall scope of homogeneous Au catalysis. Selected examples of Gold(III)-catalyzed reactions of carbonyl compounds in the presence of amines towards a variety of heterocyclic cores are given in Scheme 1 [33,34,35,36,37,38]. In most cases, AuCl3 is proposed to efficiently catalyze the formation of the heterocyclic core of the desired products (pyrroles, quinolines, furans, oxazoles, spirochromenes) through tandem amination/annulation and condensation reactions (Scheme 1, i–iii) or A3-coupling/multi-component-type reactions (Scheme 1, iv) where AuBr3 was used as a catalyst.
The use of renewable and bio-based materials has received considerable attention in the field of green chemistry over recent years. One of the top biomass-derived value-added chemicals, furfural, has been included by the US Department of Energy [39]. The combination of the aldehyde group and the aromatic ring makes furfural an appealing starting material for the synthesis of other N, O-functionalized compounds [40,41,42,43,44,45]. Among the most important classes of products derived from furfural, the trans-4,5-diaminocyclopent-2-enones (trans-DACPs) constitute versatile building blocks in the perfumery industry or in natural products, as shown in Scheme 1 [46,47,48,49,50,51]. So far, for the convenient yield of trans-DACPs, several homogeneous [52,53,54,55,56,57,58,59,60,61] and heterogeneous [62,63,64] catalytic conditions were reported; however, heteronuclear Ni(II)2Ln(III)2 (where Ln = Y, Dy) complexes [65,66,67] or metal-free systems were also proposed to promote the efficiency formation of the trans-DACPs (Scheme 1, v) [68,69,70]. One study using poly(dopamine)-supported gold nanoparticles on quartz slides as a heterogeneous surface was reported for the construction determination of a donor–acceptor Stenhouse adduct molecular layer, starting with a furfuryl-substituted CF3-isoxazolone-based acceptor molecule [71].
To date, the Lewis acid catalysts that have used in the literature for the efficient transformation of furfural into the corresponding cyclopentenone core, such as Dy(OTf)3, Sc(OTf)3, and AlCl3 with 10% mol loading, have the largest ratios in terms of the price per milligram of the catalyst used in the reaction scale of 0.5 mmol, with Sc(OTf)3 being the most expensive (Table 1). On the contrary, Cu(OTf)2 and ErCl3·6H2O have the lowest ratios in terms of the price per milligram of the catalyst used in reaction scale of 1 mmol. Although HAuCl4 seems expensive, the low loading of the catalyst accompanied by its non-toxic properties it makes it accessible for the development of the present transformation (Table S1). Thus, herein, we report—to the best of our knowledge—the first protocol that utilizes HAuCl4 for the synthesis of an extended library of trans-DACPs under mild conditions and primary or secondary amines (Scheme 1, v). It is worth noting that, in most of the above protocols, the reaction scope was limited to secondary amines. Only very recently our group reported on the polyoxometalate-driven conversion of furfural to the corresponding trans-DACPs in the presence of anilines [72].

2. Materials and Methods

2.1. Chemical Reagents

The solvents, amines, anilines, 5-methyl furfural, and furfural were purchased from Sigma-Aldrich, Fluorochem, Acros, and TCI and were used without further purification. For the catalytic reactions, the commercially available AuCl, HAuCl4, AuClPPh3, Au/TiO2, Au/Al2O3, Au/ZnO, CuCl2, CuCl, NH4Cl, MgCl2, ZnCl2, CoCl2, and FeCl3 were used without further purification.

2.2. Instrumentations

Thin-layer chromatography was performed on Millipore precoated silica gel plates (0.20 mm thick, particle size 25 μm). Nuclear magnetic resonance spectra were recorded on an Agilent 500 (1H NMR (500 MHz), 13C(H) NMR (125 MHz)). Chemical shifts for 1H NMR were reported as δ values and coupling constants were in hertz (Hz). The following abbreviations were used for spin multiplicity: s = singlet, br s = broad singlet, d = doublet, t = triplet, q = quartet, quin = quintet, dd = double of doublets, ddd = double doublet of doublets, m = multiplet. Infusion experiments were carried out on an Agilent Q-TOF Mass Spectrometer, G6540B model with Dual AJS ESI-MS. All of the compounds (dissolved in LC-MS-grade methanol) were introduced into the ESI source of the MS with a single injection of 15 μL of the sample and with a flow rate of 300 μL/min of 100% methanol as a solvent in the binary pump. The experiments were run using a Dual AJS ESI source, operating in a positive ionization mode. The source operating conditions were 330 °C Gas Temp, 8 L/min Gas Flow, Sheath Gas Temp 250 °C, Sheath Gas Flow 10 L/min, and 150 V Fragmentor. Data-dependent MS/MS analysis was performed in parallel with the MS analysis, in a centroid mode, using different collision energies (10, 20, 30, 40 V). All accurate mass measurement of the [M+H]+, [M+Na]+ [M-H]+ ions were carried out by scanning from 100 to 500 m/z. The Q-TOF was calibrated 1 h prior to the infusion experiments using a calibration mixture. Data were acquired in an external calibration mode.

2.3. Heterogeneous Catalytic Reaction between Furfural and Amines

The appropriate amount of supported gold catalysts 1% w/w (1 mol% based on furfural amount, ca. 40 mg) was placed in a 4 mL vial, followed by the addition of acetonitrile (0.4 mL), furfural (0.2 mmol), and the appropriate secondary amine (0.44 mmol). The reaction was then stirred at room temperature for 1 h. The reaction was monitored by thin-layer chromatography (TLC, Hexane/EtOAc = 1/1). After completion, the solid catalyst was separated from the reaction mixture with the use of a centrifuge and the solid residue washed twice with acetonitrile (ca 2 × 2 mL). The combined organic solvent was evaporated under vacuum and the crude reaction mixture was determined by 1H NMR spectroscopy.

2.4. Homogeneous Catalytic Reaction between Furfural and Secondary Amines

The HAuCl4 (1.5 mol%, ca. 2.5 mg) was placed in a 4 mL vial, followed by the addition of acetonitrile (0.5 mL), furfural (0.5 mmol), and the appropriate secondary amine (1.2 mmol). The reaction was then stirred at room temperature for the appropriate time. The reaction was monitored by thin-layer chromatography (TLC, Hexane/EtOAc = 1/1) and after completion, the crude mixture was concentrated under vacuum and purified by column chromatography on silica gel using a gradient mixture of EtOAc–Hexane (from 10/1 to 1/1 ratio) to afford the corresponding products in pure forms.

2.5. Homogeneous Catalytic Reaction between Furfural and Substituted Anilines

The HAuCl4 (1.5 mol%, ca. 2.5 mg) was placed in a 5 mL glass reactor (vial), followed by the addition of acetonitrile (0.5 mL), furfural (0.5 mmol), and the appropriate substituted aniline (1.2 mmol). The reaction was then stirred at room temperature for 2 h. The reaction was monitored by thin-layer chromatography (TLC, Hexane/EtOAc = 1/1) and after completion, the crude mixture was either concentrated under vacuum and purified by column chromatography on silica gel using a gradient mixture of EtOAc–Hexane (from 10/1 to 1/2 ratio) or precipitated in the solvent systems chloroform/hexane or THF/Hexane in 1/20 ratio to afford the corresponding products in pure forms.

3. Results and Discussion

3.1. Evaluation of Catalytic Conditions for the Reaction of Furfural with Morpholine

To optimize the reaction conditions, furfural (1) and morpholine (2) were selected as model substrates for the synthesis of the desired trans-4,5-dimorpholinocyclopent-2-enone 4 (Table 1). First, control experiments using 3 mol% HAuCl3 in different solvents were tested and the results are summarized in Table 1. Among the used solvents, acetonitrile was found to promote the studied transformation within 1 h and with quantitative formation of the desired product 4 (Table 1, entry 1). In the presence of other polar solvents, such as EtOAc, MeOH, EtOH, or the less-polar DCM, DCE, CHCl3, or even non-polar toluene, a mixture of aminal 3 and the product 4 were observed in different ratios (Table 1). Similar results were also observed in the absence of a catalyst and over a prolonged period of time (18 h) in several solvents (Table S2). Only protic solvents MeOH and EtOH and polar DMF were found to promote the studied transformation over a prolonged period of time, leading to a mixture with the desired 4 as the major product (Table S2 entries 2, 3, and 13). For comparison, the reaction profile was also studied in the absence of HAuCl4 and in CH3CN as the chosen solvent. The absence of a catalyst, and at a prolonged reaction time of 18 h, revealed the formation of a mixture of aminal 3 and the 4; however, no reaction completion was observed (Figure 1). The structure of 3 was determined by NMR and compared with the literature data [73].
Table
Table 1. Solvent screening in the presence of HAuCl4.
Table 1. Solvent screening in the presence of HAuCl4.
Chemistry 05 00029 i001
Solvent [a]1 (%)3 (%)4 (%)
CH3CN--100
EtOAc87517
MeOH-6337
EtOH-6733
DCM136720
DCE97516
DMC107020
Toluene88012
CHCl312799
[a] Reaction conditions: 1 (0.2 mmol), 2 (0.44 mmol), solvent (0.2 mL), 25 °C. All yields were determined from the crude 1H NMR mixture of the reaction, and calculated by the addition of 1,3,5-trimethoxybenzene (0.1 mmol) as an internal standard.
Then, the development of the catalytic condition in the presence of different gold catalysts was performed in acetonitrile and the results are summarized in Table 2. Commercially available heterogeneous catalysts containing gold nanoparticles (AuNPs) in 1 % w/w, such as Au/TiO2, Au/Al2O3, and Au/ZnO2, were tested at 25 °C. In all cases, the corresponding catalyst was used in 1 mol% based on the amount of AuNPs (20 mg), 0.2 mmol of the furfural, and 0.44 mmol of the morpholine, in 0.2 mL of CH3CN. We observed that aminal 3 was formed as the major product (Table 2, entries 2–4). When TiO2 and Al2O3 were used as heterogeneous catalysts, similar results were observed along with a significant amount of the unreactive furfural 1 (Table 2, entries 4 and 5). These results indicate that AuNPs and the acidic supports TiO2 and Al2O3 are not able to catalyze the formation of the desired trans-DACP 4 under the present conditions. For this reason, we further studied the catalytic activity of the commercially available gold salts, i.e., AuCl, (pTolyl)3AuCl, and HAuCl4, under the above conditions. The Au(I) salts shows media catalytic activity towards the reaction between 1 and 2 (Table 2, entries 6–8); however, HAuCl4 was found to efficiently mediate the studied transformation, quantitatively leading to the desired product 4 (Table 2, entry 9). Based on these results, we continued with the evaluation of the catalytic conditions and found that HAuCl4 can catalyze this transformation even at the lower amount of 1.5 mol% within 2 h (Table 2, 11). However, using 1 mol%, no reaction completion was observed within 2 h and the desired 4 was formed in a 77 % yield (Table 2, entry 12). It is worth noting that when increasing the scale of the reaction to 0.5 mmol and 1 mmol of 1, a quantitative formation of 4 was observed within 15 min and 30 min, respectively (Table 2, entries 13 and 14). For comparison, HCl was added into the reaction mixture at 3 mol%; however, a lower yield of the desired 4 was measured (40%) with a significant amount of aminal 3 (29%) and an identified product (31%) was observed by 1H NMR of the crude reaction mixture (Table 2, entry 15). These results agree with a Lewis-catalyzed process by the presence of Au(I) and Au(III), with Au(III) as a hard Lewis acid, to preferentially bind to the lone pairs of heteroatoms such as O, N, and S. The oxophilic Au(III) complexes may be employed to accelerate chemoselective reactions for which piphilic Au(I) complexes are less efficient. To support this hypothesis, different commercially available salts (CuCl2, CuCl, NH4Cl, MgCl2, ZnCl2, CoCl2, FeCl3) were also tested under the same conditions (Table S3). However, in all cases, mixtures of 3 and 4 were observed, with the latter predominating in most cases, accompanied by an unidentified product in significant amounts (Table S3, entries 5, 6, and 13). In most cases, a higher amount of the salt (ca. > 6 mol%) was required for reaction completion (Table S3). Photoirradiation conditions, with a xenon lamp as the light source, were also performed, using either heterogeneous or homogeneous conditions (Table S4). In all cases, no significant changes were measured in the product yields or reaction conversion by 1H NMR spectroscopy.

3.2. Application of Catalytic Conditions to the Synthesis of trans-DACPs 4, 4a–4d, and 5a–5o

Based on the above optimum conditions, we further examined the possible application into the direct synthesis of a series of substituted trans-DACPs (Scheme 2). Several substituted secondary amines (1.1 mmol) and furfural (0.5 mmol) were added into 0.5 mL of CH3CN in the presence of 1.5 mol% of HAuCl4 at 25 °C. Indeed, under these conditions, the substituted trans-DACPs (4, 4a–4d) were synthesized and isolated in moderate to high yields of 52–95% (Scheme 2) using the commonly available starting secondary amines, such as morpholine, pyrrolidine, 3-methylpyrolidine, dimethylamine, and N-methylaniline, respectively.
With these encouraging results, we further examined the possible application of the present optimum conditions using substituted anilines (1.1 mmol) instead of secondary amines. As far as we know, only aniline was used in sporadic examples for the synthesis of the corresponding trans-DACPs; however, low yields were reported. Only polyoxometalates were reported to successfully drive the conversion of furfural to the corresponding trans-DACPs in the presence of anilines [72]. Thus, a series of substituted anilines (1.1 mmol) were studied in the presence of 0.5 mmol of furfural in 0.5 mL of CH3CN at room temperature. Indeed, under the proposed conditions, a series of substituted trans-DACPs (5a–5o) were synthesized and isolated in moderate to high isolated yields of 54–89% (Scheme 3). More specifically, substituted anilines with electron withdrawing groups (5a–5m) were found to lead the reaction in higher yields; however, the corresponding aniline and p-toluidine derivatives were formed in lower yields (5n, 54% and 5o, 59%). In addition to this observation, the m-NO2-substituted aniline reacted in lower yields than the corresponding p-NO2 aniline, leading to the desired trans-DACPs 5l and 5m of 68% and 65%, respectively. It is interesting to note that 5a and 5e were also synthesized at the 5 mmol lab-scale and were isolated in 77% and 73% yields, respectively, in the presence of 3 mol% of HAuCl4 and in 3 mL of CH3CN (Scheme 3, values in parentheses).
It is worth noting that p-MeO-aniline (pKb~8.6) does not lead to the desired cyclopentanone derivate; however, the corresponding imine 6 was formed quantitatively (Scheme 4). Accordingly, using the primary aliphatic amine n-butylamine (pKb~3.2) and benzylamine (pKb~4.6), the corresponding imines 7 and 8 were observed as the only product, even at the prolonged reaction time (18 h) (Scheme 4). It is noting that, in the presence of pyrrolidine, an equimolar mixture of the desired trans-4,5-N,N-disubstituted cyclopent-2-en-1-one 9a and the thermodynamic 2,4-disusbtituted cyclopentenone 9b was observed; however, no reaction process was observed in the presence of diisopropylamine, 1H-indole, or L-proline (Scheme 4). Based on these results, it seems that the protocol was applied to anilines and secondary amines with pKb higher than ca. 9.

3.3. Reaction Profile Evaluation of the Reaction between Furfural and o-Phenylenediamine

To synthetically explore the present catalytic conditions using aryl diamines, we initially studied the reaction between o-phenylenediamine (9) and furfural (1). The reaction process was monitored by 1H NMR, and after completion (the consumption of furfural based on TLC), four products were observed: the corresponding trans-DACPs (13) in a 26% yield, 2-furyl-benzimidizole (11) as the major one in a 36% yield, 1,2-disubstituted benzimidazole (12) in a 14% yield, and the corresponding imine (10) in a 24% yield (Scheme 5). By increasing the amount of furfural and catalyst and at a prolonged reaction time, the desired product 13 was formed in a lower yield (16%); however, the corresponding benzimidazole derivatives 11 and 12 were formed in 23% and 61% yields, respectively (Scheme 5). This result agrees with our previous work on benzimidazole synthesis from aldehydes and o-phenylenediamine catalyzed by Au/TiO2 [74].

3.4. Proposed Mechanistic Pathway for the Reaction of Furfural with Anilines

From a mechanistic point of view, during the present catalytic conditions, the oxophilic Au(III) complexes mediated the initial formation of I and the further transformation to intermediate II (Scheme 6). The nucleophilic attack of the amine to the 3-position of the cyclopentenone core of II led to the formation of Stenhouse salt intermediate III, which subsequently transformed to the final product through a 4π-conrotatory electrocyclization pathway with the exclusive trans-diastereoisomer (trans-DACPs) (Scheme 6). This plausible pathway is in agreement with the literature reports in which the corresponding Stenhouse salt, derived by the reaction of furfural with aniline, was isolated and characterized by XRD [67]. It is worth noting that no reaction process was observed by 1H NMR when 5-methylfurfural was mixed with 4-chloroanilne, a result that further supports the proposed mechanism.

4. Conclusions

Herein is presented, for the first time, the efficient approach of a series of trans-N,N-4,5-substituted-diaminocyclopent-2-enones from furfural and anilines mediated by Gold(III) chloride. With the proposed protocol, a library of trans-DACPs were synthesized and isolated with good to high yields, using a low amount of the catalyst (1.5 mol%), under ambient conditions, in the absence of additives and using short reaction times. Under the same conditions, secondary amines were also reacted with furfural to produce the corresponding trans-DACPs in high yields. The present catalytic synthetic protocol has an extended substrate scope with high yields and represents, to the best of our knowledge, the first gold-driven paradigm as an efficient method for the formation of the cyclopentenones core under mild reaction conditions.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/chemistry5010029/s1, Tables S1–S4, NMR and HRMS data, NMR spectra.

Author Contributions

M.A.T. and I.N.L. conceived the study. M.A.T. performed the experimental methodology, catalytic study, and product analysis. I.N.L. supervised the study and wrote and corrected the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research was co-financed by Greece and the European Union (European Social Fund ESF) through the Operational Program “Human Resources Development, Education and Lifelong Learning 2014–2020” in the context to the project “Photocatalytic transformations using hybrid catalytic systems of metal nanoparticles and polyoxometalates for the synthesis of high added value organic compounds” (MIS:5047897). The Center of Interdisciplinary Research and Innovation of Aristotle University of Thessaloniki (CIRI-AUTH) is also acknowledged for providing access to the Large Research Infrastructure and Instrumentation of the NMR Laboratory in the Chemical Engineering Department, AUTH.

Data Availability Statement

Not applicable.

Acknowledgments

We thank C. Gabriel and D.A. Sarigiannis ([email protected]) of the HERACLES Research Center, KEDEK, Laboratory of Environmental Engineering (EnvE-Lab), Department of Chemical Engineering, AUTH, Greece, for using the LC-TOF apparatus and performing the HRMS experiments. The authors would like to acknowledge the Center of Interdisciplinary Research and Innovation of Aristotle University of Thessaloniki, Greece, for access to the Large Research Infrastructure and Instrumentation of the Nuclear Magnetic Resonance Laboratory, AUTH, for performing the NMR experiments. We also thank Alexios D. Kouvelas (MSc student, Department of Chemistry, A.U.Th., [email protected]) for repeating the compound-cleaning procedures and recording the new NMR spectra.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Hendrich, C.M.; Sekine, K.; Koshikawa, T.; Tanaka, K.; Hashmi, A.S.K. Homogeneous and Heterogeneous Gold Catalysis for Materials Science. Chem. Rev. 2021, 121, 9113–9163. [Google Scholar] [CrossRef] [PubMed]
  2. Zheng, Z.; Ma, X.; Cheng, X.; Zhao, K.; Gutman, K.; Li, T.; Zhang, L. Homogeneous Gold-Catalyzed Oxidation Reactions. Chem. Rev. 2021, 121, 8979–9038. [Google Scholar] [CrossRef] [PubMed]
  3. Mato, M.; Franchino, A.; Garcıa-Morales, C.; Echavarren, A.M. Gold-Catalyzed Synthesis of Small Rings. Chem. Rev. 2021, 121, 8613–8684. [Google Scholar] [CrossRef] [PubMed]
  4. Kaur, N. Gold and Silver Assisted Synthesis of Five-Membered Oxygen and Nitrogen Containing Heterocycles. Synth. Commun. 2019, 49, 1459–1485. [Google Scholar] [CrossRef]
  5. Pflasterer, D.; Hashmi, A.S.K. Gold Catalysis in Total Synthesis –Recent Achievements. Chem. Soc. Rev. 2016, 45, 1331–1367. [Google Scholar] [CrossRef]
  6. Hashmi, A.S.K. Dual Gold Catalysis. Acc. Chem. Res. 2014, 47, 864–876. [Google Scholar] [CrossRef]
  7. Mikami, Y.; Dhakshinamoorthy, A.; Alvaro, M.; Garcıa, H. Catalytic Activity of Unsupported Gold Nanoparticles. Catal. Sci. Technol. 2013, 3, 58–69. [Google Scholar] [CrossRef]
  8. Ishida, T.; Murayama, T.; Taketoshi, A.; Haruta, M. Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes. Chem. Rev. 2022, 120, 464–525. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  9. Stratakis, M.; Lykakis, I.N. Nanogold(0)-Catalyzed Addition of Heteroelement σ-Linkages to Functional Groups. Synthesis 2019, 51, 2435–2454. [Google Scholar] [CrossRef]
  10. Hutchings, G.J. Heterogeneous Gold Catalysis. ACS Cent. Sci. 2018, 4, 1095–1101. [Google Scholar] [CrossRef] [Green Version]
  11. Takale, B.S.; Bao, M.; Yamamoto, Y. Gold Nanoparticle (AuNPs) and Gold Nanopore (AuNPore) Catalysts in Organic Synthesis. Org. Biomol. Chem. 2014, 12, 2005–2027. [Google Scholar] [CrossRef] [PubMed]
  12. Liu, X.; He, L.; Liu, Y.-M.; Cao, Y. Supported Gold Catalysis: From Small Molecule Activation to Green Chemical Synthesis. Acc. Chem. Res. 2014, 47, 793–804. [Google Scholar] [CrossRef] [PubMed]
  13. Mitsudomea, T.; Kaneda, K. Gold Nanoparticle Catalysts for Selective Hydrogenations. Green Chem. 2013, 15, 2636–2654. [Google Scholar] [CrossRef]
  14. Mielby, J.; Kegnζs, S.; Fristrup, P. Gold Nanoparticle-Catalyzed Formation of Nitrogen Containing Compounds—From Mechanistic Understanding to Synthetic Exploitation. ChemCatChem 2012, 4, 1037–1047. [Google Scholar] [CrossRef]
  15. Stratakis, M.; Garcia, H. Catalysis by Supported Gold Nanoparticles: Beyond Aerobic Oxidative Processes. Chem. Rev. 2012, 112, 4469–4506. [Google Scholar] [CrossRef] [PubMed]
  16. Corma, A.; Garcia, H. Supported Gold Nanoparticles as Catalysts for Organic Reactions. Chem. Soc. Rev. 2008, 37, 2096–2126. [Google Scholar] [CrossRef] [PubMed]
  17. Dorel, R.; Echavarren, A.M. Gold(I)-Catalyzed Activation of Alkynes for the Construction of Molecular Complexity. Chem. Rev. 2015, 115, 9028–9072. [Google Scholar] [CrossRef] [Green Version]
  18. Fürstner, A. Gold and Platinum Catalysis—A Convenient Tool for Generating Molecular Complexity. Chem. Soc. Rev. 2009, 38, 3208–3221. [Google Scholar] [CrossRef]
  19. Zi, W.; Toste, F.D. Recent Advances in Enantioselective Gold Catalysis. Chem. Soc. Rev. 2016, 45, 4567–4589. [Google Scholar] [CrossRef]
  20. Sengupta, S.; Shi, X. Recent Advances in Asymmetric Gold Catalysis. ChemCatChem 2010, 2, 609–619. [Google Scholar] [CrossRef]
  21. Meera, G.; Rohit, K.R.; Treesa, G.S.S.; Anilkumar, G. Advances and Prospects in Gold-Catalyzed C−H Activation. Asian J. Org. Chem. 2020, 9, 144–161. [Google Scholar] [CrossRef]
  22. de Haro, T.; Nevado, C. On Gold-Mediated C-H Activation Processes. Synthesis 2011, 16, 2530–2539. [Google Scholar]
  23. Shu, X.; Zhang, M.; He, Y.; Frei, H.; Toste, F.D. Dual Visible Light Photoredox and Gold-Catalyzed Arylative Ring Expansion. J. Am. Chem. Soc. 2014, 136, 5844–5847. [Google Scholar] [CrossRef] [PubMed]
  24. Sahoo, B.; Hopkinson, M.N.; Glorius, F. Combining Gold and Photoredox Catalysis: Visible Light-Mediated Oxy- and Aminoarylation of Alkenes. J. Am. Chem. Soc. 2013, 135, 5505–5508. [Google Scholar] [CrossRef]
  25. Witzel, S.; Hashmi, A.S.K.; Xie, J. Light in Gold Catalysis. Chem. Rev. 2021, 121, 8868–8925. [Google Scholar] [CrossRef]
  26. Primo, A.; Corma, A.; Garcıa, H. Titania Supported Gold Nanoparticles as Photocatalyst. Phys. Chem. Chem. Phys. 2011, 13, 886–910. [Google Scholar] [CrossRef]
  27. Rocchigiani, L.; Bochmann, M. Recent Advances in Gold(III) Chemistry: Structure, Bonding, Reactivity, and Role in Homogeneous Catalysis. Chem. Rev. 2021, 121, 8364–8451. [Google Scholar] [CrossRef]
  28. Collado, A.; Nelson, D.J.; Nolan, S.P. Optimizing Catalyst and Reaction Conditions in Gold(I) Catalysis−Ligand Development. Chem. Rev. 2021, 121, 8559–8612. [Google Scholar] [CrossRef]
  29. Jazzar, R.; Soleilhavoup, M.; Bertrand, G. Cyclic (Alkyl)- and (Aryl)-(amino)carbene Coinage Metal Complexes and Their Applications. Chem. Rev. 2020, 120, 4141–4168. [Google Scholar] [CrossRef]
  30. Lu, Z.; Hammond, G.B.; Xu, B. Improving Homogeneous Cationic Gold Catalysis through a Mechanism-Based Approach. Acc. Chem. Res. 2019, 52, 1275–1288. [Google Scholar] [CrossRef]
  31. Kumar, R.; Nevado, C. Cyclometalated Gold(III) Complexes: Synthesis, Reactivity, and Physicochemical Properties. Angew. Chem. Int. Ed. 2017, 56, 1994–2015. [Google Scholar] [CrossRef] [PubMed]
  32. Lee, D.; Kim, S.M.; Hirao, H.; Hong, S.H. Gold(I)/Gold(III)-Catalyzed Selective Synthesis of N -Sulfonyl Enaminone Isomers from Sulfonamides and Ynones via Two Distinct Reaction Pathways. Org. Lett. 2017, 19, 4734–4737. [Google Scholar] [CrossRef] [PubMed]
  33. Arcadi, A.; Giuseppe, S.D.; Marinelli, F.; Rossi, E. Conversion of Homochiral Amines and α-Amino Esters to their Chiral 1,2,3,5-Substituted Pyrrole Derivatives via Gold-Catalysed Amination/Annulation Reactions of 2-Propynyl-1,3-dicarbonyl Compounds. Tetrahedron Asymmetry 2001, 19, 2715–2720. [Google Scholar] [CrossRef]
  34. Shu, X.-Z.; Liu, X.-Y.; Xiao, H.-Q.; Ji, K.-G.; Guo, L.-N.; Liang, Y.-M. Tandem Gold(III)-Catalyzed Amination-Intramolecular Hydroamination Reactions of 1-En-4-yn-3-ols with Sulfonamides: Efficient Approach to Highly Substituted Pyrroles. Adv. Synth. Catal. 2008, 350, 243–248. [Google Scholar] [CrossRef]
  35. Atechian, S.; Nock, N.; Norcross, R.D.; Ratni, H.; Thomas, A.W.; Verron, J.; Masciadri, R. New Vistas in Quinoline Synthesis. Tetrahedron 2007, 63, 2811–2823. [Google Scholar] [CrossRef]
  36. Li, J.; Liu, L.; Ding, D.; Sun, J.; Ji, Y.; Dong, J. Gold(III)-Catalyzed Three-Component Coupling Reaction (TCC) Selective toward Furans. Org. Lett. 2013, 15, 2884–2887. [Google Scholar] [CrossRef]
  37. Wachenfeldt, H.V.; Röse, P.; Paulsen, F.; Loganathan, N.; Strand, D. Catalytic Three-Component Domino Reaction for the Preparation of Trisubstituted Oxazoles. Chem. Eur. J. 2013, 19, 7982–7988. [Google Scholar] [CrossRef]
  38. Kidwai, M.; Jahan, A.; Mishra, N.K. Gold(III) Chloride (HAuCl4·3H2O) in PEG: A New and Efficient Catalytic System for the Synthesis of Functionalized Spirochromenes. Appl. Catal. A Gen. 2012, 425–426, 35–43. [Google Scholar] [CrossRef]
  39. Bozell, J.J.; Petersen, G.R. Technology Development for the Production of Biobased Products from Biorefinery Carbohydrates—The US Department of Energy’s “Top 10” Revisited. Green Chem. 2010, 12, 539–554. [Google Scholar] [CrossRef]
  40. Peters, F.N. Industrial Uses of Furans. Ind. Eng. Chem. 1939, 31, 178–180. [Google Scholar] [CrossRef]
  41. Lukes, R.M.; Wilson, C.L. Reactions of Furan Compounds. XI. Side Chain Reactions of Furfural and Furfuryl Alcohol over Nickel-Copper and Iron-Copper Catalysts. J. Am. Chem. Soc. 1951, 73, 4790–4794. [Google Scholar] [CrossRef]
  42. Hashmi, A.S.K.; Wölfle, M.; Teles, J.; Frey, W. Bisphenols from Furfurals by Organocatalysis and Gold Catalysis. Synlett 2007, 11, 1747–1752. [Google Scholar] [CrossRef]
  43. Mariscal, R.; Maireles-Torres, P.; Ojeda, M.; Sádaba, I.; López Granados, M. Furfural: A Renewable and Versatile Platform Molecule for the Synthesis of Chemicals and Fuels. Energy Environ. Sci. 2016, 9, 1144–1189. [Google Scholar] [CrossRef]
  44. Tšupova, S.; Rominger, F.; Rudolph, M.; Hashmi, A.S.K. Synthesis of Phenols from Hydroxymethylfurfural (HMF). Green Chem. 2016, 18, 5800–5805. [Google Scholar] [CrossRef]
  45. Simeonov, S.P.; Nunes, J.P.M.; Guerra, K.; Kurteva, V.B.; Afonso, C.A.M. Synthesis of Chiral Cyclopentenones. Chem. Rev. 2016, 116, 5744–5893. [Google Scholar] [CrossRef] [PubMed]
  46. Takano, I.; Yasuda, I.; Nishijima, M.; Hitotsuyanagi, Y.; Takeya, K.; Itokawa, H. New Cephalotaxus Alkaloids from Cephalotaxus harringtonia var. drupacea. J. Nat. Prod. 1996, 59, 965–967. [Google Scholar] [CrossRef]
  47. Inagaki, F.; Kinebuchi, M.; Miyakoshi, N.; Mukai, C. Formal Synthesis of (+)-Nakadomarin A. Org. Lett. 2010, 12, 1800–1803. [Google Scholar] [CrossRef]
  48. Dong, G. Recent Advances in the Total Synthesis of Agelastatins. Pure Appl. Chem. 2010, 82, 2231–2246. [Google Scholar] [CrossRef] [Green Version]
  49. Kusama, T.; Tanaka, N.; Sakai, K.; Gonoi, T.; Fromont, J.; Kashiwada, Y.; Kobayashi, J. Agelamadins A and B, Dimeric Bromopyrrole Alkaloids from a Marine Sponge Agelas sp. Org. Lett. 2014, 16, 3916–3918. [Google Scholar] [CrossRef]
  50. Araki, A.; Tsuda, M.; Kubota, T.; Mikami, Y.; Fromont, J.; Kobayashi, J. Nagelamide J, a Novel Dimeric Bromopyrrole Alkaloid from a Sponge Agelas Species. Org. Lett. 2007, 9, 2369–2371. [Google Scholar] [CrossRef]
  51. Hanessian, S.; Vakiti, R.R.; Dorich, S.; Banerjee, S.; Lecomte, F.; DelValle, J.R.; Zhang, J.; Deschênes-Simard, B. Total Synthesis of Pactamycin. Angew. Chem. Int. Ed. 2011, 50, 3497–3500. [Google Scholar] [CrossRef] [PubMed]
  52. Lewis, K.; Mulquiney, C. Rearrangements in the Furan Series. II. The Reaction Between Furfuraldehyde and Aromatic Amines. Aust. J. Chem. 1979, 32, 1079–1092. [Google Scholar] [CrossRef]
  53. Lewis, K.G.; Mulquiney, C.E. Aspects of the Formation and use of Stenhouse Salts and Related Compounds. Tetrahedron 1977, 33, 463–475. [Google Scholar] [CrossRef]
  54. Hofmann, T. Characterization of the Chemical Structure of Novel Colored Maillard Reaction Products from Furan-2-carboxaldehyde and Amino Acids. J. Agric. Food Chem. 1998, 46, 932–940. [Google Scholar] [CrossRef]
  55. Li, S.-W.; Batey, R.A. Mild Lanthanide(iii) Catalyzed Formation of 4,5-Diaminocyclopent-2-enones from 2-Furaldehyde and Secondary Amines: A Domino Condensation/Ring-Opening/Electrocyclization Process. Chem. Commun. 2007, 36, 3759–3761. [Google Scholar] [CrossRef]
  56. Nunes, J.P.M.; Afonso, C.A.M.; Caddick, S. Synthesis of 2,4-Bifunctionalised Cyclopentenones from 2-Furaldehyde. RSC Adv. 2013, 3, 14975. [Google Scholar] [CrossRef]
  57. Procopio, A.; Costanzo, P.; Curini, M.; Nardi, M.; Oliverio, M.; Sindona, G. Erbium(III) Chloride in Ethyl Lactate as a Smart Ecofriendly System for Efficient and Rapid Stereoselective Synthesis of trans -4,5-Diaminocyclopent-2-enones. ACS Sustain. Chem. Eng. 2013, 1, 541–544. [Google Scholar] [CrossRef]
  58. Ramesh, D.; Reddy, T.S.; Narasimhulu, M.; Rajaram, S.; Suryakiran, N.; Mahesh, K.C.; Venkateswarlu, Y. Efficient and Rapid Stereoselective Synthesis of trans -4,5-Diaminocyclopent-2-enones by Acidic Ionic Liquid under Solvent-free Conditions. Chem. Lett. 2009, 38, 586–587. [Google Scholar] [CrossRef]
  59. Hiscox, A.; Ribeiro, K.; Batey, R.A. Lanthanide(III)-Catalyzed Synthesis of trans -Diaminocyclopentenones from Substituted Furfurals and Secondary Amines via a Domino Ring-Opening/4π-Electrocyclization Pathway. Org. Lett. 2018, 20, 6668–6672. [Google Scholar] [CrossRef]
  60. Gomes, R.F.A.; Esteves, N.R.; Coelho, J.A.S.; Afonso, C.A.M. Copper(II) Triflate As a Reusable Catalyst for the Synthesis of trans -4,5-Diamino-cyclopent-2-enones in Water. J. Org. Chem. 2018, 83, 7509–7513. [Google Scholar] [CrossRef]
  61. Peewasan, K.; Merkel, M.P.; Fuhr, O.; Powell, A.K. A Designed and Potentially Decadentate Ligand for use in Lanthanide(III) Catalysed Biomass Transformations: Targeting Diastereoselective trans-4,5-Diaminocyclopentenone Derivatives. Dalton Trans. 2020, 49, 2331–2336. [Google Scholar] [CrossRef] [PubMed]
  62. Estevão, M.S.; Afonso, C.A.M. Synthesis of trans-4,5-diaminocyclopent-2-enones from furfural catalyzed by Er(III) immobilized on silica. Tetrahedron Lett. 2017, 58, 302–304. [Google Scholar] [CrossRef]
  63. Deng, Q.; Wang, R. Heterogeneous MOF Catalysts for the Synthesis of trans-4,5-Diaminocyclopent-2-enones from Furfural and Secondary Amines. Catal. Commun. 2019, 120, 11–16. [Google Scholar] [CrossRef]
  64. Gomes, R.F.A.; Cavaca, L.A.S.; Goncalves, J.M.; Ramos, R.; Peixoto, A.F.; Arias-Serrano, B.I.; Afonso, C.A.M. Silica-Supported Copper for the Preparation of Trans- 4,5-Diamino-Cyclopent-2-Enones under Continuous Flow Conditions. ACS Sustain. Chem. Eng. 2021, 9, 16038–16043. [Google Scholar] [CrossRef]
  65. Griffiths, K.; Kumar, P.; Mattock, J.D.; Abdul-Sada, A.; Pitak, M.B.; Coles, S.J.; Navarro, O.; Vargas, A.; Kostakis, G.E. Efficient Ni II 2 Ln III 2 Electrocyclization Catalysts for the Synthesis of trans-4,5-Diaminocyclopent-2-enones from 2-Furaldehyde and Primary or Secondary Amines. Inorg. Chem. 2016, 55, 6988–6994. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  66. Griffiths, K.; Gallop, C.W.D.; Abdul-Sada, A.; Vargas, A.; Navarro, O.; Kostakis, G.E. Heteronuclear 3 d/Dy III Coordination Clusters as Catalysts in a Domino Reaction. Chem. Eur. J. 2015, 21, 6358–6361. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  67. Sampani, S.I.; McGown, A.; Vargas, A.; Abdul-Sada, A.; Tizzard, G.J.; Coles, S.J.; Spencer, J.; Kostakis, G.E. Solvent-Free Synthesis and Key Intermediate Isolation in Ni2Dy2 Catalyst Development in the Domino Ring-Opening Electrocyclization Reaction of Furfural and Amines. J. Org. Chem. 2019, 84, 6858–6867. [Google Scholar] [CrossRef]
  68. Nardi, M.; Costanzo, P.; De Nino, A.; Di Gioia, M.L.; Olivito, F.; Sindona, G.; Procopio, A. Water Excellent Solvent for the Synthesis of Bifunctionalized Cyclopentenones from Furfural. Green Chem. 2017, 19, 5403–5411. [Google Scholar] [CrossRef]
  69. Liu, J.; Yu, J.; Zhu, M.; Li, J.; Zheng, X.; Wang, L. Novel Role of p-Toluenesulfonamide in the Preparation of 4,5-Diaminocyclopent-2-enones. Synthesis 2013, 45, 2165–2170. [Google Scholar]
  70. Di Gioia, M.; Nardi, M.; Costanzo, P.; De Nino, A.; Maiuolo, L.; Oliverio, M.; Procopio, A. Biorenewable Deep Eutectic Solvent for Selective and Scalable Conversion of Furfural into Cyclopentenone Derivatives. Molecules 2018, 23, 1891. [Google Scholar] [CrossRef] [Green Version]
  71. Nánási, D.E.; Kunfi, A.; Abrahám, A.; Mayer, P.J.; Mihály, J.; Samu, G.F.; Kiss, E.; Mohai, M.; London, G. Construction and Properties of Donor−Acceptor Stenhouse Adducts on Gold Surfaces. Langmuir 2021, 37, 3057–3066. [Google Scholar] [CrossRef] [PubMed]
  72. Tzani, M.A.; Fountoulaki, S.; Lykakis, I.N. Polyoxometalate-Driven Ease Conversion of Valuable Furfural to trans-N,N-4,5-Diaminocyclopenten-2-ones. J. Org. Chem. 2022, 87, 2601–2615. [Google Scholar] [CrossRef] [PubMed]
  73. Pereira, J.G.; António, J.P.M.; Mendonça, R.; Gomes, R.F.A.; Afonso, C.A.M. Rediscovering Aminal Chemistry: Copper(II) Catalysed Formation under Mild Conditions. Green Chem. 2020, 22, 7484–7490. [Google Scholar] [CrossRef]
  74. Tzani, M.A.; Gabriel, C.; Lykakis, I.N. Selective Synthesis of Benzimidazoles from o-Phenylenediamine and Aldehydes Promoted by Supported Gold Nanoparticles. Nanomaterials 2020, 10, 2405. [Google Scholar] [CrossRef]
Chemistry 05 00029 sch001 550
Scheme 1. (Upper) Gold(III)-catalyzed organic transformation in the presence of amines. (Lower) Gold(III)-catalyzed transformation of furfural into trans-DACPs.
Scheme 1. (Upper) Gold(III)-catalyzed organic transformation in the presence of amines. (Lower) Gold(III)-catalyzed transformation of furfural into trans-DACPs.
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Figure 1. Reaction profile study in the absence of a catalyst and in CH3CN.
Figure 1. Reaction profile study in the absence of a catalyst and in CH3CN.
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Scheme 2. Synthetic application for the substituted trans-DACPs (4, 4a–4d) formation from the reaction of 1 and secondary amines mediated by the presence of HAuCl4.
Scheme 2. Synthetic application for the substituted trans-DACPs (4, 4a–4d) formation from the reaction of 1 and secondary amines mediated by the presence of HAuCl4.
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Scheme 3. Synthesis of substituted trans-DACPs (5a-5o) from the reaction of 1 and anilines mediated by the presence of HAuCl4.
Scheme 3. Synthesis of substituted trans-DACPs (5a-5o) from the reaction of 1 and anilines mediated by the presence of HAuCl4.
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Scheme 4. Amine structure limitations under the present protocol conditions.
Scheme 4. Amine structure limitations under the present protocol conditions.
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Scheme 5. Reaction between o-phenylenediamine and furfural mediated by HAuCl4.
Scheme 5. Reaction between o-phenylenediamine and furfural mediated by HAuCl4.
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Scheme 6. Plausible reaction paths for the transformation of furfural into trans-DACPs mediated by HAuCl3.
Scheme 6. Plausible reaction paths for the transformation of furfural into trans-DACPs mediated by HAuCl3.
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Table
Table 2. Gold catalyst screening for the synthesis of trans-DACPs 4 from 1 and 2.
Table 2. Gold catalyst screening for the synthesis of trans-DACPs 4 from 1 and 2.
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EntryCatalyst/mol% [a]Time1 (%)3 (%)4 (%)
1No catalyst1 h185824
1Au/TiO2 / 1 mol%1 h-100-
2Au/Al2O3 / 1 mol%1 h892-
3Au/ZnO / 1 mol%1 h137413
4TiO2 1 h3268-
5Al2O3 1 h2575-
6AuCl / 3 mol%1 h125137
7 [b]AuCl / 3 mol%1 h163747
8 [c](pTolyl)3PAuCl / 3 mol%1 h143333
9HAuCl4 / 3 mol%1 h--100
10HAuCl4/ 3 mol%15 min141868
11HAuCl4/ 1.5 mol%2 h--100
12HAuCl4/ 1 mol%2 h91477
13 [b]HAuCl4/ 3 mol%15 min--100
14 [d]HAuCl4/ 3 mol%30 min--100
15 [b,e]HCl / 3 mol%1 h-2940
[a] Reaction conditions: 1 (0.2 mmol), 2 (0.44 mmol), CH3CN (0.2 mL), 25 °C. All yields were determined from the crude 1H NMR mixture of the reaction, and calculated by the addition of 1,3,5-trimethoxybenzene (0.1 mmol) as an internal standard. [b] 1 (0.5 mmol), 2 (1.1 mmol), CH3CN (0.5 mL), 25 °C. [c] 20% of an unidentified product was observed by 1H NMR. [d] 1 (1 mmol), 2 (2.2 mmol), solvent-free conditions, 25 °C. [e] 31% of an unidentified product was observed by 1H NMR.
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Tzani, M.A.; Lykakis, I.N. Gold(III) Chloride-Mediated Transformation of Furfural to the trans-N,N-4,5-Diaminocyclopent-2-enones in the Presence of Anilines. Chemistry 2023, 5, 393-405. https://doi.org/10.3390/chemistry5010029

AMA Style

Tzani MA, Lykakis IN. Gold(III) Chloride-Mediated Transformation of Furfural to the trans-N,N-4,5-Diaminocyclopent-2-enones in the Presence of Anilines. Chemistry. 2023; 5(1):393-405. https://doi.org/10.3390/chemistry5010029

Chicago/Turabian Style

Tzani, Marina A., and Ioannis N. Lykakis. 2023. "Gold(III) Chloride-Mediated Transformation of Furfural to the trans-N,N-4,5-Diaminocyclopent-2-enones in the Presence of Anilines" Chemistry 5, no. 1: 393-405. https://doi.org/10.3390/chemistry5010029

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