Next Article in Journal
Degradation of Sulfamethoxazole Using Iron-Doped Titania and Simulated Solar Radiation
Previous Article in Journal
PdI2-Based Catalysis for Carbonylation Reactions: A Personal Account
Previous Article in Special Issue
Synthesis and Organocatalytic Asymmetric Nitro-aldol Initiated Cascade Reactions of 2-Acylbenzonitriles Leading to 3,3-Disubstituted Isoindolinones
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 9
Issue 7
10.3390/catal9070611
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Hydrosoluble Complexes Bearing Tris(pyrazolyl)methane Sulfonate Ligand: Synthesis, Characterization and Catalytic Activity for Henry Reaction

by
Abdallah G. Mahmoud
,
Luísa M. D. R. S. Martins
*,
M. Fátima C. Guedes da Silva
* and
Armando J. L. Pombeiro
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa Av. Rovisco Pais, 1049-001 Lisboa, Portugal
*
Authors to whom correspondence should be addressed.
Catalysts 2019, 9(7), 611; https://doi.org/10.3390/catal9070611
Submission received: 2 July 2019 / Revised: 15 July 2019 / Accepted: 16 July 2019 / Published: 18 July 2019
(This article belongs to the Special Issue Catalysts for Henry Reaction)
Browse Figures
Versions Notes

Abstract

:
The catalytic activity of the water-soluble scorpionate coordination compounds [Cu(κ-NN′O-Tpms)2] (1), [Mn(Tpms)2] (2) and Li[FeCl2(κ-NN′N″-Tpms)] (3) [Tpms = tris(pyrazolyl)-methane sulfonate, O3SC(pz)3−], were studied towards the (Henry) reaction between benzaldehyde and nitromethane or nitroethane in aqueous medium to afford, respectively, 2-nitro-1-phenylethanol or 2-nitro-1-phenylpropanol, the latter in the syn and the anti diastereoisomeric forms. Complex 1 exhibited the highest activity under the optimum experimental conditions and was used to broaden the scope of the reaction to include several aromatic aldehydes achieving yields up to 94%.

1. Introduction

Scorpionate is a term coined by Trofimenko [1] to describe a special class of poly(pyrazolyl) compounds, which are derived from two or more N-deprotonated pyrazole rings bound to a main group atom (e.g., boron, carbon, aluminium, indium, gallium, silicon, and germanium) through one of the ring nitrogens [1,2,3,4,5,6]. Tris(pyrazolyl)methanes (Tpm, Figure 1) were reported for the first time in 1937 [7]. However, up to mid-90s, their properties and coordination chemistry remained unexplored due to the difficulties of their preparation in good yields, until Reger has reviewed some effective synthetic protocols to prepare Tpm compounds in high yields [8,9,10].
Significant developments have been made in the application of C-scorpionate Tpm based complexes as catalysts due to their chelating versatility resulting from, e.g., a change between the bidentate and tridentate binding modes [2,11,12,13,14]. They have been reported as catalyst precursors for oxidation [12,13,15,16,17,18], hydroformylation [19], hydrogenation [20,21], alkane hydroxylation [22], benzene carbonylation [23], olefin polymerization [24,25,26], nitrene transfer reactions [27], nitroaldol condensation [11,28], azide-alkyne cycloaddition [29], and Heck C–C coupling [30,31].
Tpm based compounds are highly soluble and stable in all common organic solvents but not in water. In the beginning of this century, Kläui et al. [32] obtained a novel class of water soluble scorpionates by addition of sulfurtrioxide–trimethylamine complex to lithiated HC(pz)3 to produce the anionic hydrosoluble tris(pyrazolyl)methane sulfonate (Tpms) (Scheme 1).
The hydrophilic nature of Tpms and its complexes makes them potentially useful in the area of enzyme modelling and catalysis, where systems that operate in aqueous solution are actively sought after due to the inherently potential sustainable processes [11]. Although the coordination properties of Tpms have been well studied towards diverse metal centers, the use of Tpms-containing hydrosoluble complexes in aqueous medium catalysis is limited to scarce examples, in particular for oxidation [16,33,34,35], hydroformylation [19], and hydrogenation [20] reactions. The catalytic activity of Tpms-metal complexes for nitroaldol (Henry) reaction has not yet been investigated.
Nitroaldol condensation [36] is carried out by coupling a nitroalkane with an aldehyde or ketone to produce the corresponding β-nitro alcohol. This reaction has found various applications [37,38,39], the produced β-nitro alcohols can be converted into other valuable intermediates, including α-nitro ketones by oxidation [40], β-amino alcohols by reduction [41], or nitroalkenes by dehydration [42].
Activation of the carbonyl group using Lewis acidic metal compounds for catalytic Henry reaction is an approach that has been intensively studied and performed with (i) a well-defined complex [28,43,44,45,46,47,48,49,50,51,52,53], (ii) an in situ generated complex by addition of a metal salt and a ligand [54,55,56,57,58,59], or (iii) a metal organic framework (MOF) [60,61,62]. In some instances a base is used to facilitate the deprotonation of the nitroalkane [56,63,64].
On the basis of the above considerations, herein we report the catalytic performance of well-defined hydrosoluble Cu(II), Mn(II), and Fe(II) complexes 1–3 bearing a Tpms ligand for Henry reaction in a homogeneous aqueous medium, for which a high Lewis acid character of the catalyst should constitute a favorable feature.

2. Results and Discussion

2.1. Synthesis and Characterization of Complexes

Reacting Cu(II), Mn(II) salts (e.g., chlorides, nitrates, or acetates) or iron(II) chloride with Li(Tpms), under air and at room temperature, lead to the formation of complexes [Cu(κ-NN′O-Tpms)2] (1), [Mn(Tpms)2] (2), and Li[FeCl2(κ-NN′N″-Tpms)] (3), respectively (Scheme 2). Compound 2 is new, whereas reports on 1 [65] and 3 [33] have been found. A different experimental procedure for obtaining 1 has been followed which led to the authentication of its structure by single crystal X-ray diffraction. A novel structure for Li(Tpms) was also obtained and is described in the Supplementary Material file.
Complexes 1–3 are stable in air both in the solid state and in solution. While 2 and 3 show a good solubility in water, DMSO and MeCN, 1 can be dissolved only in hot water after stirring for several hours, or upon addition of few drops of 0.1 M NH4OH to raise the pH to 9. The formulations of 1–3 were confirmed by spectroscopic and analytical data (see experimental section). As expected, compounds 1 and 2 are paramagnetic.
The IR spectra of the compounds exhibit a set of bands with diverse intensities typical of the Tpms ligand [66], in particular the ν(C=C) and ν(C=N) vibrations of the pyrazolyl groups in the range of ca. 1651–1506 cm−1, in addition to the ν(S=O) in the range of 1064–1036 cm−1.
ESI-MS spectra for the complexes were obtained in water solutions. In the negative mode a common peak corresponding to [O3SC(pz)3]− is revealed and represents the base peak; in the positive mode the spectra of the complexes do not show the [M]+ molecular ion peak, but a set of other peaks assigned to the compounds fragmentations.

2.2. Description of the X-ray Crystal Structure

The molecular structure of 1 was established by single crystal X-ray diffraction (SCXRD) analysis. The crystals were obtained as described in the experimental section. Selected crystallographic data and structure refinement details are provided in Table S1. Selected bond distances and angles are listed in Table S2.
Complex 1 crystallized in the orthorhombic space group Pbca, its asymmetric unit comprising the copper metal cation and one Tpms unit (Figure 2). The metal presents a slightly distorted N4O2 octahedral geometry, with the ligands exhibiting κ-NN′O coordination modes. The N-donor atoms occupy the equatorial positions with Cu–N bond distances of 1.9829(16) and 1.9898(16) Å, and the O-atoms stand on the axial positions rendering Cu–O lengths of 2.3480(16) Å. The former values are shorter than those found in the Cu(I) complex [Cu(PPh3)(κ-NN′O-Tpms)] [2.003(3) and 2.032(2) Å] [65], on account of the metal lower oxidation state in the latter. However, it is also lower than those found in the copper(II) complex with 2,2,2-tris(pyrazol-1-yl)ethyl methanesulfonate ligands, working as NNN-chelators [1.999(3)–2.347(3) Å] [67]. Although the long Cu–O dimension in 1 can be due to Jahn-Teller distortion [68,69,70], it is similar to that found in the Cu(I) complex [65]. The coordinated pyrazolyl rings and sulfonate group restrict the intra-ligand N–Cu–N and N–Cu–O angles to the range 83.32(7)°–86.28(7)°, it is therefore shorter than the expected 90°.

2.3. Catalytic Activity

Compounds 1–3 were tested, under atmospheric mild homogeneous reaction conditions, as catalysts for nitroaldol coupling of nitromethane with benzaldehyde in water to afford 2-nitro-1-phenylethanol. Using as a model the reaction of benzaldehyde with nitromethane (see Table 1), using 5 mol% of catalyst in water as sole solvent for 24 h and at 75 °C, the Cu(II) complex 1 exhibited the highest catalytic activity for the Henry reaction (Table 1, entries 1–3). Therefore, it was employed for further exploration of several reaction variables in order to find the optimum conditions to afford the highest yield of the product.
The reaction progression with time has been monitored in water using 5 mol% of the catalyst, at 75 °C (Table 1, entries 1 and 4–9). 2-Nitro-1-phenylethanol yield raised gradually with time up to 77% upon 48 h, and a further extension of the reaction time did not lead to a significant change.
Performing the reaction in different solvents (Table 1, entries 10–20, and Figure 3) revealed the following points: using solely a protic solvent (e.g., water, methanol, or ethanol) led to higher 2-nitro-1-phenylethanol yields than the use of other organic solvents for the same period of time (Table 1, entries 10–15); MeOH gave the highest yield of 61%. Generally, by using a 1:1 combination of water and organic co-solvent (Table 1, entries 16–20) better yields were obtained. A 1:1 mixture of water and MeOH gave a yield (59%) very close to that obtained using MeOH alone (Table 1, entries 10 and 16). Finally, the use of a 1:1 immiscible mixture of CH2Cl2 or toluene with water in a bi-phasic catalytic system gave lower product yields (28% and 31%, respectively) when compared to other miscible aqueous combinations (Table 1, compare entries 16–20).
It was observed that in a mixture of water and MeOH, the rise in temperature up to 100 °C led to an increase in the reaction yield to 89% after 48 h (Table 1, entries 21–23). Also, increasing the catalyst loading from 0.5 mol% to 5 mol% raised the reaction yield from 14% to 78% (Table 1, entries 22 and 24–26).
In the presence of an additional catalytic amount of a base (i.e., 5 mol% of catalyst 1 and a similar amount of triethylamine), the conversion was quantitative after only 12 h in water, at room temperature (Table 1, entry 27). With Cu(II) salts as catalysts, only 12 to 38% conversions were achieved after 24 h at 75 °C (Table 1, entries 28–31). The reaction does not show any progression under solvent-free conditions or in the absence of the catalytic metal species (Table 1, entries 32 and 33). With triethylamine and in the absence of catalyst 1, a conversion of 41% was obtained after 12 h at room temperature (Table 1, entry 34).
By replacing nitromethane in the model reaction with nitroethane, the β-nitro alcohol is produced in the diastereoisomeric syn and the anti forms of 2-nitro-1-phenylpropanol (Table 2). In a water/MeOH (1:1) mixture, using 5 mol% of catalyst 1 at 100 °C a yield of 85% (maximum) was reached in 48 h exhibiting superior selectivity for the syn isomer (Table 2, entries 1–4). The presence of 5 mol% of triethylamine improved the reaction performance in terms of yield (97%) at ambient temperature and in a shorter time and but with a significant decrease in selectivity (Table 2, entry 5).
In accordance with previous studies, [71,72,73,74] the mechanism of the reaction involves metal assisted (upon coordination) deprotonation of nitroalkane to produce the nitronate species, and activation of the aldehyde for its electrophilic attack to the nitronate. Therefore, the Cu(II) complex 1 acts efficiently as a Lewis acid for the aforementioned activation process and, furthermore, the Tpms ligand can behave as a base to enhance the nitroalkane deprotonation.
Based on the study of several variables, it was found that the best reaction conditions to obtain the highest possible yield of β-nitro alcohols using catalyst 1 (5 mol%) is by heating the reaction mixture at 100 °C for 48 h in a mixture of water and MeOH.
The scope of the catalytic reaction was broadened to include different para-substituted aromatic aldehydes (Table 3) under the aforementioned optimum conditions.
Using either nitromethane or nitroethane, the reaction proceeded smoothly to afford the corresponding β-nitro alcohols with yields up to 94%, exhibiting higher selectivity towards the syn isomer if nitroethane was employed. The results show that the aromatic aldehydes with electron-donating substituents (OCH3 or CH3, Table 3, entries 1–4) exhibit a lower reactivity than those bearing electron-withdrawing groups (NO2, Br or Cl, Table 3, entries 7–12) due to the higher electrophilicity of the aldehyde in the latter case. In comparison to the scarce examples found in the literature for the catalytic nitroaldol reaction in water, using catalysts based on different metals (Table S3), the conversions obtained in this work are comparable, or better in some cases, taking into consideration the indicated reaction conditions such as temperature, amount of catalyst, and reaction time [43,44,60,61,62,75,76,77,78,79,80].

3. Materials and Methods

3.1. General Procedures and Instrumentation

All synthetic procedures were performed in air. Reagents and solvents were obtained from commercial sources and used without further purification. Li(Tpms) [32] and complex 3 [33] were synthesized using the reported procedures.
C, H, N and S elemental analyses were carried out by the Microanalytical services of the Instituto Superior Técnico. Infrared spectra (4000–400 cm−1) were obtained in a Cary 630 FTIR spectrometer (Agilent, Santa Clara, CA, USA); wavenumbers are in cm−1; abbreviations: s, strong; m, medium; w, weak. Electrospray mass spectra were obtained with a Varian 500 MS LC Ion Trap Mass Spectrometer equipped with an electrospray (ESI) ion source. For electrospray ionization, the drying gas and flow rate were optimized according to the particular sample with 35 p.s.i. nebulizer pressure. The compounds were observed in the negative and positive modes (capillary voltage = 80–105 V). 1H spectra were obtained using Bruker Advance III 300 or 400 MHz UltraShield Magnet spectrometer (Bruker, Billerica, MA, USA), at ambient temperature.

3.2. Synthesis of Complexes

3.2.1. Synthesis of [Cu(Tpms)2] (1)

To a MeOH solution (10 mL) of Cu(NO3)2.2.5H2O (38 mg, 0.165 mmol), Li(Tpms) (100 mg, 0.33 mmol) was added at room temperature to produce a blue-sky precipitate immediately. The solution was stirred for an additional 3 hours. The blue-sky crystalline precipitate was filtered off, washed with MeOH, and dried under vacuum.
X-ray quality crystals of 1 were obtained after dissolving the compound (25 mg) in an acetonitrile: 0.1 M NH4OH aqueous solution (10:1.5 mL) following slow evaporation in air. Compound 1 was also obtained when using different starting Cu2+ metal salts (e.g., acetate or chloride) or different stoichiometric ratios of the reagents.
Yield = 71%, based on copper (76 mg). Elemental analysis calcd (%) for C20H18CuN12O6S2 (650.11 g/mol): C 36.95, H 2.79, N 25.85, S 9.86; found: C 37.24, H 2.83, N 25.72, S 9.89. FTIR (KBr pellet), ν (cm−1): 3167 w [ν(C−H)]; 1635 m, 1506 w [ν(C=C) and ν(C=N)]; 1095 m, 1076 m, 1053 m, 1036 m [ν(S=O)]; 650 s [ν(S−C]; 479 m [ν(Cu−N]. ESI-MS−/+ in H2O (m/z assignment, % intensity): 293 ([O3SC(pz)3]−, 100); 356 ([Cu{O3SC(pz)3}]+, 100).

3.2.2. Synthesis of [Mn(Tpms)2] (2)

To a solution of Mn(NO3)2·4H2O (42 mg, 0.165 mmol) in EtOH (5 mL) was added, with constant stirring, Li(Tpms) (100 mg, 0.33 mmol) in EtOH (10 mL). A white precipitate was immediately observed, and the solution was stirred for 3 hours at room temperature. The solid was isolated by filtration, washed with cold EtOH, and dried under vacuum.
Yield = 68%, based on manganese (72 mg). Elemental analysis calcd (%) for C20H18MnN12O6S2.2H2O (677.53 g/mol): C 35.45, H 3.27, N 24.81, S 9.77; found: C 35.83, H 2.98, N 24.33, S 10.19. FTIR (KBr pellet), ν (cm−1): 3167 m [ν(C−H)]; 1636 m, 1532 w[ν(C=C) and ν(C=N)]; 1101 m, 1065 m, 1051 m, 1036 s [ν(S=O)]; 657 m, 639 s [ν(S−C)]; 446 m [ν(Mn−N]. ESI-MS−/+ in H2O (m/z assignment, % intensity): 293 ([O3SC(pz)3]−, 100); 348 ([Mn{O3SC(pz)3}]+, 100).

3.3. General Procedure for β-Nitro Alcohols Synthesis

In a typical experiment, a mixture of the nitroalkane (1.5 mmol), the catalyst (0.025 mmol) and 2 mL of solvent, was prepared with constant stirring for 15 minutes. Then, the aldehyde (0.5 mmol) was added. The solution stirred in atmospheric conditions and for the time intervals indicated in Table 1, Table 2 and Table 3. After the desired reaction time, 3 mL water were added to the solution and extracted with diethyl ether (3 × 10 mL). The combined extracts were dried over Na2SO4 (anhydrous), and the mixture filtered off. The diethyl ether was removed using vacuum, and the organic residue was analyzed by 1H NMR spectroscopy, in CDCl3, to calculate the yield of β-nitro alcohol as no other products were detected.
Using 1H NMR spectroscopy to calculate the β-nitro alcohol yields constitutes an efficient way, as proved in several reports [45,63,75,80,81,82,83]. The ratio between the anti and syn diastereoisomers of 1-phenyl-2-nitropropanol, formed by the nitroaldol coupling using nitroethane, was also determined by 1H NMR spectroscopy. Indeed, the vicinal coupling constants values between the α-O–C–H and the α-N–C–H protons identify the isomers (anti-isomer: J = 7–9 Hz; syn-isomer J = 3.2–4 Hz) [84,85].

3.4. X-ray Structure Determination of Compounds

An X-ray quality crystal of 1 and of Li(Tpms) were immersed in cryo-oil, mounted in a Nylon loop and measured at ambient temperature. Intensity data were collected in a Bruker AXS-KAPPA APEX II PHOTON 100 diffractometer (Bruker, Billerica, MA, USA) with graphite monochromated Mo-Kα (0.71069 Å) radiation. Data were collected using omega scans of 0.5° per frame and a full sphere of data was obtained. Cell parameters were retrieved using Bruker SMART [86] software and refined using Bruker SAINT [86] on all the observed reflections. SADABS program was used for applying absorption corrections [87]. The structure was solved by direct methods using SIR97 package [88] and refined with SHELXL-2014/7 [89]. The WinGX System-Version 2014.1 was used for the calculations [90]. Least square refinements with anisotropic thermal motion parameters for all the non-hydrogen atoms and isotropic ones for the remaining atoms were employed.
CCDC 1936856 (1) and 1936857 [Li(Tpms)] contain the supplementary crystallographic data for this paper. This data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

4. Conclusions

The tris(pyrazolyl)-methane sulfonate compounds [Cu(κ-NN’O-Tpms)2] (1), [Mn(Tpms)2] (2) and Li[FeCl2(κ-NN′N″-Tpms)] (3) were the first Tpms complexes to be investigated as catalysts towards the nitroaldol (Henry) reaction between benzaldehyde and nitromethane to afford the corresponding 2-nitro-1-phenylethanol. Complex 1 was the most active (89% yield) under the following optimum reaction conditions: 5 mol% of catalyst, 1:1 water:MeOH solvent mixture, 100 °C, and for 48 h. Reacting benzaldehyde with nitroethane in the presence of 1, and under the given experimental conditions, produced 2-nitro-1-phenylpropanol in the syn and the anti diastereoisomeric forms, with a total yield of 85% and a higher selectivity towards the former. The scope of the reaction was broadened to include several aromatic aldehydes, which were reacted with any of the nitroalkanes. Higher yields (up to 94%) were obtained with aldehydes possessing electron-withdrawing groups.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4344/9/7/611/s1: Figure S1: ORTEP diagram of Li(Tpms) with displacement ellipsoids drawn at 40% probability level and partial atom labelling scheme, Figure S2: Structural fragment representing the two chains of the 1D polymer of Li(Tpms), Figure S3: 1H NMR spectrum (CDCl3; 400 MHz) of crude product from nitroaldol condensation of benzaldehyde with nitromethane using 5 mol% of catalyst 1 (Table 1, entry 23), Figure S4: 1H NMR spectrum (CDCl3; 400 MHz) of crude product from nitroaldol condensation of benzaldehyde with nitroethane using 5 mol% of catalyst 1 (Table 2, entry 2), Table S1: Crystallographic data and structure refinement details for Li(Tpms) and 1, Table S2: Selected bond distances (Å) and angles (°) for Li(Tpms) and 1, Table S3: Comparison of various catalytic systems for Henry reaction of benzaldehyde with nitroethane in aqueous medium.

Author Contributions

L.M.D.R.S.M. and A.G.M. conceived and designed the experiments; M.F.C.G.d.S. performed, solved and discussed the single-crystal X-ray diffraction data; A.G.M., M.F.C.G.d.S., L.M.D.R.S.M. and A.J.L.P. discussed the whole data and wrote the paper. All authors read and approved the manuscript.

Funding

This research was funded by Fundação para a Ciência e a Tecnologia (FCT), Portugal (projects UID/QUI/00100/2019, PTDC/QEQ-ERQ/1648/2014 and PTDC/QEQ-QIN/3967/2014).

Acknowledgments

This work was financed by national funds from the Foundation for Science and Technology FCT/MCTES (UID/QUI/00100/2019), Portugal. AGM is thankful to the CATSUS doctoral program of FCT for his PhD fellowship (SFRH/BD/106006/2014). LMDRSM acknowledges FCT/MCTES through PTDC/QEQ-ERQ/1648/2014. The authors acknowledge the Portuguese NMR Network (IST-UL Centre) for access to the NMR facility and the IST Node of the Portuguese Network of Mass-spectrometry for the ESI-MS measurements.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Trofimenko, S. Scorpionates: The Coordination Chemistry of Polypyrazolylborate Ligands; Imperial College Press: London, UK, 1999; ISBN 978-1-86094-172-6. [Google Scholar]
  2. Bigmore, H.R.; Lawrence, S.C.; Mountford, P.; Tredget, C.S. Coordination, organometallic and related chemistry of tris(pyrazolyl)methane ligands. Dalton Trans. 2005, 635–651. [Google Scholar] [CrossRef]
  3. Pettinari, C.; Pettinari, R. Metal derivatives of poly(pyrazolyl)alkanes: I. Tris(pyrazolyl)alkanes and related systems. Coord. Chem. Rev. 2005, 249, 525–543. [Google Scholar] [CrossRef]
  4. Breakell, K.R.; Patmore, D.J.; Storr, A. Synthesis of pyrazolyl-borate, -aluminate, -gallate, and -indate ligands, and their chelating properties towards cobalt(II), nickel(II), copper(II), and zinc(II). J. Chem. Soc. Dalton Trans. 1975, 749–754. [Google Scholar] [CrossRef]
  5. Pullen, E.E.; Rheingold, A.L.; Rabinovich, D. Methyltris(pyrazolyl)silanes: New tripodal nitrogen-donor ligands. Inorg. Chem. Commun. 1999, 2, 194–196. [Google Scholar] [CrossRef]
  6. Steiner, A.; Stalke, D. Poly(pyrazolyl)germanium(II) and -Tin(II) Derivatives-Tuneable Monoanionic Ligands and Dinuclear Cationic Cages. Inorg. Chem. 1995, 34, 4846–4853. [Google Scholar] [CrossRef]
  7. Hückel, W.; Bretschneider, H. N-Tripyrazolyl-methan. Chem. Ber. 1937, 9, 2024–2026. [Google Scholar] [CrossRef]
  8. Reger, D.L. Tris(Pyrazolyl)Methane Ligands: The Neutral Analogs of Tris(Pyrazolyl)Borate Ligands. Comments Inorg. Chem. 1999, 21, 1–28. [Google Scholar] [CrossRef]
  9. Reger, D.L.; Grattan, T.C.; Brown, K.J.; Little, C.A.; Lamba, J.J.S.; Rheingold, A.L.; Sommer, R.D. Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)methane]Mn(CO)3}SO3CF3 complexes: Comparison of ligand donor properties. J. Organomet. Chem. 2000, 607, 120–128. [Google Scholar] [CrossRef]
  10. Reger, D.L.; Grattan, T.C. Synthesis of Modified Tris(pyrazolyl)methane Ligands: Backbone Functionalization. Synthesis 2003, 2003, 350–356. [Google Scholar] [CrossRef]
  11. Martins, L.M.D.R.S.; Pombeiro, A.J.L. Water-Soluble C-Scorpionate Complexes-Catalytic and Biological Applications. Eur. J. Inorg. Chem. 2016, 2016, 2236–2252. [Google Scholar] [CrossRef]
  12. Martins, L.M.D.R.S.; Pombeiro, A.J.L. C-scorpionate rhenium complexes and their application as catalysts in Baeyer-Villiger oxidation of ketones. Inorg. Chim. Acta 2017, 455, 390–397. [Google Scholar] [CrossRef]
  13. Martins, L.M.D.R.S.; Pombeiro, A.J.L. Tris(pyrazol-1-yl)methane metal complexes for catalytic mild oxidative functionalizations of alkanes, alkenes and ketones. Coord. Chem. Rev. 2014, 265, 74–88. [Google Scholar] [CrossRef]
  14. Martins, L.M.D.R.S. C-scorpionate complexes: Ever young catalytic tools. Coord. Chem. Rev. 2019, 396, 89–102. [Google Scholar] [CrossRef]
  15. Santos, A.M.; Kühn, F.E.; Bruus-Jensen, K.; Lucas, I.; Romão, C.C.; Herdtweck, E. Molybdenum(VI) cis-dioxo complexes bearing (poly)pyrazolyl-methane and -borate ligands: Syntheses, characterization and catalytic applications. J. Chem. Soc. Dalton Trans. 2001, 1332–1337. [Google Scholar] [CrossRef]
  16. McLauchlan, C.C.; Weberski, M.P.; Greiner, B.A. Synthesis, catalytic activity, phosphatase inhibition activity, and X-ray structural characterization of vanadium scorpionate complexes, (Tpms)VCl2(DMF) and (Tpms)VOCl(DMF). Inorg. Chim. Acta 2009, 362, 2662–2666. [Google Scholar] [CrossRef]
  17. Duarte, T.A.G.; Carvalho, A.P.; Martins, L.M.D.R.S. Ultra-fast and selective oxidation of styrene to benzaldehyde catalyzed by a C-scorpionate Cu(ii) complex. Catal. Sci. Technol. 2018, 8, 2285–2288. [Google Scholar] [CrossRef]
  18. Duarte, T.A.G.; Carvalho, A.P.; Martins, L.M.D.R.S. Styrene oxidation catalyzed by copper(II) C-scorpionates in homogenous medium and immobilized on sucrose derived hydrochars. Catal. Today 2019. [Google Scholar] [CrossRef]
  19. Kläui, W.; Schramm, D.; Schramm, G. Tripodal oxygen and tripodal nitrogen ligands in hydroformylation reactions: Formation of novel rhodium(III) carbonyl bis(acyl) complexes. Inorg. Chim. Acta 2004, 357, 1642–1648. [Google Scholar] [CrossRef]
  20. Nagaraja, C.M.; Nethaji, M.; Jagirdar, B.R. Tris(pyrazolyl)methane Sulfonate Complexes of Iridium: Catalytic Hydrogenation of 3,3-Dimethyl-1-butene. Organometallics 2007, 26, 6307–6311. [Google Scholar] [CrossRef]
  21. Ribeiro, A.P.C.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. Carbon dioxide-to-methanol single-pot conversion using a C-scorpionate iron(ii) catalyst. Green Chem. 2017, 19, 4811–4815. [Google Scholar] [CrossRef]
  22. Yamaguchi, M.; Iida, T.; Yamagishi, T. Syntheses of mixed-ligand ruthenium(II) complexes with a terpyridine or a tris (pyrazolyl) methane and a bidentate ligand: Their application for catalytic hydroxylation of alkanes. Inorg. Chem. Commun. 1998, 1, 299–301. [Google Scholar] [CrossRef]
  23. Kläui, W.; Schramm, D.; Peters, W. Photoinduced C− H Activation and Catalytic Carbonylation of Benzene—New Features of a Tris (pyrazolyl) methanesulfonato (Tpms) Rhodium (I) Complex. Eur. J. Inorg. Chem. 2001, 3113–3117. [Google Scholar] [CrossRef]
  24. Bigmore, H.R.; Zuideveld, M.A.; Kowalczyk, R.M.; Cowley, A.R.; Kranenburg, M.; McInnes, E.J.L.; Mountford, P. Synthesis, Structures, and Olefin Polymerization Capability of Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands. Inorg. Chem. 2006, 45, 6411–6423. [Google Scholar] [CrossRef]
  25. Bigmore, H.R.; Dubberley, S.R.; Kranenburg, M.; Lawrence, S.C.; Sealey, A.J.; Selby, J.D.; Zuideveld, M.A.; Cowley, A.R.; Mountford, P. A remarkable inversion of structure–activity dependence on imido N-substituents with varying co-ligand topology and the synthesis of a new borate-free zwitterionic polymerisation catalyst. Chem. Commun. 2006, 436–438. [Google Scholar] [CrossRef]
  26. García-Orozco, I.; Quijada, R.; Vera, K.; Valderrama, M. Tris(pyrazolyl)methane–chromium(III) complexes as highly active catalysts for ethylene polymerization. J. Mol. Catal. A Chem. 2006, 260, 70–76. [Google Scholar] [CrossRef]
  27. Liang, S.; Jensen, M.P. Half-Sandwich Scorpionates as Nitrene Transfer Catalysts. Organometallics 2012, 31, 8055–8058. [Google Scholar] [CrossRef]
  28. Rocha, B.G.M.; Mac Leod, T.C.O.; Guedes da Silva, M.F.C.; Luzyanin, K.V.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. Ni II, Cu II and Zn II complexes with a sterically hindered scorpionate ligand (Tpms Ph) and catalytic application in the diasteroselective nitroaldol (Henry) reaction. Dalton Trans. 2014, 43, 15192–15200. [Google Scholar] [CrossRef]
  29. Mahmoud, A.G.; Martins, L.M.D.R.S.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Copper complexes bearing C-scorpionate ligands: Synthesis, characterization and catalytic activity for azide-alkyne cycloaddition in aqueous medium. Inorg. Chim. Acta 2018, 483, 371–378. [Google Scholar] [CrossRef]
  30. Matias, I.A.S.; Ribeiro, A.P.C.; Martins, L.M.D.R.S. New C-scorpionate nickel(II) catalyst for Heck C–C coupling under unconventional conditions. J. Organomet. Chem. 2019, 896, 32–37. [Google Scholar] [CrossRef]
  31. Martins, L.; Wanke, R.; Silva, T.; Pombeiro, A.; Servin, P.; Laurent, R.; Caminade, A.-M.; Martins, L.M.D.R.S.; Wanke, R.; Silva, T.F.S.; et al. Novel Methinic Functionalized and Dendritic C-Scorpionates. Molecules 2018, 23, 3066. [Google Scholar] [CrossRef]
  32. Kläui, W.; Berghahn, M.; Rheinwald, G.; Lang, H. Tris(pyrazolyl)methanesulfonates: A Novel Class of Water-Soluble Ligands. Angew. Chem. Int. Ed. 2000, 39, 2464–2466. [Google Scholar] [CrossRef]
  33. Silva, T.F.S.; Alegria, E.C.B.A.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. Half-Sandwich Scorpionate Vanadium, Iron and Copper Complexes: Synthesis and Application in the Catalytic Peroxidative Oxidation of Cyclohexane under Mild Conditions. Adv. Synth. Catal. 2008, 350, 706–716. [Google Scholar] [CrossRef]
  34. Silva, T.F.S.; Luzyanin, K.V.; Kirillova, M.V.; da Silva, M.F.G.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. Novel Scorpionate and Pyrazole Dioxovanadium Complexes, Catalysts for Carboxylation and Peroxidative Oxidation of Alkanes. Adv. Synth. Catal. 2010, 352, 171–187. [Google Scholar] [CrossRef]
  35. Martins, L.M.D.R.S.; Alegria, E.C.B.A.; Smoleński, P.; Kuznetsov, M.L.; Pombeiro, A.J.L. Oxorhenium Complexes Bearing the Water-Soluble Tris(pyrazol-1-yl)methanesulfonate, 1,3,5-Triaza-7-phosphaadamantane, or Related Ligands, as Catalysts for Baeyer–Villiger Oxidation of Ketones. Inorg. Chem. 2013, 52, 4534–4546. [Google Scholar] [CrossRef]
  36. Henry, L. Nitro-alcohols. C. R. Hebd. Seances Acad. Sci. 1895, 120, 1265. [Google Scholar]
  37. Rosini, G. The Henry (nitroaldol) reaction. In Comprehensive Organic Synthesis; Trost, B.M., Fleming, I., Heathcock, C.H., Eds.; Elsevier ltd.: Oxford, UK, 1991; pp. 321–340. [Google Scholar]
  38. Luzzio, F.A. The Henry reaction: Recent examples. Tetrahedron 2001, 57, 915–945. [Google Scholar] [CrossRef]
  39. Palomo, C.; Oiarbide, M.; Laso, A. Recent Advances in the Catalytic Asymmetric Nitroaldol (Henry) Reaction. Eur. J. Org. Chem. 2007, 2007, 2561–2574. [Google Scholar] [CrossRef]
  40. Rosini, G.; Ballini, R.; Petrini, M.; Marotta, E.; Righi, P. RECENT PROGRESS IN THE SYNTHESIS AND REACTIVITY OF NITROKETONES. A REVIEW. Org. Prep. Proced. Int. 1990, 22, 707–746. [Google Scholar] [CrossRef]
  41. Colvin, E.W.; Beck, A.K.; Seebach, D. Improved Nitroaldol Reactions and Reductive Routes to Vicinal Aminoalcohols. Helv. Chim. Acta 1981, 64, 2264–2271. [Google Scholar] [CrossRef]
  42. Buckley, G.D.; Scaife, C.W. Aliphatic nitro-compounds. Part I. Preparation of nitro-olefins by dehydration of 2-nitro-alcohols. J. Chem. Soc. 1947, 1471–1472. [Google Scholar] [CrossRef]
  43. Sutradhar, M.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. A new cyclic binuclear Ni(II) complex as a catalyst towards nitroaldol (Henry) reaction. Catal. Commun. 2014, 57, 103–106. [Google Scholar] [CrossRef]
  44. Karmakar, A.; Hazra, S.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Synthesis, structure and catalytic applications of amidoterephthalate copper complexes in the diastereoselective Henry reaction in aqueous medium. New J. Chem. 2014, 38, 4837–4846. [Google Scholar] [CrossRef]
  45. Ribeiro, A.P.C.; Karabach, Y.Y.; Martins, L.M.D.R.S.; Mahmoud, A.G.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Nickel((ii))-2-amino-4-alkoxy-1,3,5-triazapentadienate complexes as catalysts for Heck and Henry reactions. RSC Adv. 2016, 6, 29159–29163. [Google Scholar] [CrossRef]
  46. Martins, N.M.R.; Mahmudov, K.T.; da Silva, M.F.C.G.; Martins, L.M.D.R.S.; Guseinov, F.I.; Pombeiro, A.J.L. 1D Zn(II) coordination polymer of arylhydrazone of 5,5-dimethylcyclohexane-1,3-dione as a pre-catalyst for the Henry reaction. Catal. Commun. 2016, 87, 49–52. [Google Scholar] [CrossRef]
  47. Tiago, G.A.O.; Mahmudov, K.T.; Guedes da Silva, M.F.C.; Ribeiro, A.P.C.; Huseynov, F.E.; Branco, L.C.; Pombeiro, A.J.L. Copper(II) coordination polymers of arylhydrazone of 1H-indene-1,3(2H)-dione linked by 4,4′-bipyridineor hexamethylenetetramine: Evaluation of catalytic activity in Henry reaction. Polyhedron 2017, 133, 33–39. [Google Scholar] [CrossRef]
  48. Kopylovich, M.N.; Mizar, A.; Guedes da Silva, M.F.C.; Mac Leod, T.C.O.; Mahmudov, K.T.; Pombeiro, A.J.L. Template Syntheses of Copper(II) Complexes from Arylhydrazones of Malononitrile and their Catalytic Activity towards Alcohol Oxidations and the Nitroaldol Reaction: Hydrogen Bond-Assisted Ligand Liberation and E/Z Isomerisation. Chem. A Eur. J. 2013, 19, 588–600. [Google Scholar] [CrossRef]
  49. Gurbanov, A.V.; Huseynov, F.E.; Mahmoudi, G.; Maharramov, A.M.; Guedes da Silva, F.C.; Mahmudov, K.T.; Pombeiro, A.J.L. Mononuclear nickel(II) complexes with arylhydrazones of acetoacetanilide and their catalytic activity in nitroaldol reaction. Inorg. Chim. Acta 2018, 469, 197–201. [Google Scholar] [CrossRef]
  50. Sutradhar, M.; Alegria, E.C.B.A.; Roy Barman, T.; Guedes da Silva, M.F.C.; Mahmudov, K.T.; Guseynov, F.I.; Pombeiro, A.J.L. New copper(II) tetramer with arylhydrazone of barbituric acid and its catalytic activity in the oxidation of cyclic C5–C8 alkanes. Polyhedron 2016, 117, 666–671. [Google Scholar] [CrossRef]
  51. Ma, Z.; Gurbanov, A.V.; Maharramov, A.M.; Guseinov, F.I.; Kopylovich, M.N.; Zubkov, F.I.; Mahmudov, K.T.; Pombeiro, A.J.L. Copper(II) arylhydrazone complexes as catalysts for CH activation in the Henry reaction in water. J. Mol. Catal. A Chem. 2017, 426, 526–533. [Google Scholar] [CrossRef]
  52. Sutradhar, M.; Roy Barman, T.; Pombeiro, A.J.L.; Martins, L.M.D.R.S.; Sutradhar, M.; Roy Barman, T.; Pombeiro, A.J.L.; Martins, L.M.D.R.S. Ni(II)-Aroylhydrazone Complexes as Catalyst Precursors Towards Efficient Solvent-Free Nitroaldol Condensation Reaction. Catalysts 2019, 9, 554. [Google Scholar] [CrossRef]
  53. Mahmoud, A.G.; Guedes da Silva, M.F.C.; Śliwa, E.I.; Smoleński, P.; Kuznetsov, M.L.; Pombeiro, A.J.L. Copper(II) and Sodium(I) Complexes based on 3,7-Diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane-5-oxide: Synthesis, Characterization, and Catalytic Activity. Chem. Asian J. 2018, 13, 2868–2880. [Google Scholar] [CrossRef]
  54. Trost, B.M.; Yeh, V.S.C.; Ito, H.; Bremeyer, N. Effect of Ligand Structure on the Zinc-Catalyzed Henry Reaction. Asymmetric Syntheses of (−)-Denopamine and (−)-Arbutamine. Org. Lett. 2002, 4, 2621–2623. [Google Scholar]
  55. Evans, D.A.; Seidel, D.; Rueping, M.; Lam, H.W.; Shaw, J.T.; Downey, C.W. A New Copper Acetate-Bis(oxazoline)-Catalyzed, Enantioselective Henry Reaction. J. Am. Chem. Soc. 2003, 125, 12692–12693. [Google Scholar] [CrossRef] [Green Version]
  56. Lu, S.-F.; Du, D.-M.; Zhang, S.-W.; Xu, J. Facile synthesis of C2-symmetric tridentate bis(thiazoline) and bis(oxazoline) ligands and their application in the enantioselective Henry reaction. Tetrahedron Asymmetry 2004, 15, 3433–3441. [Google Scholar] [CrossRef]
  57. Blay, G.; Domingo, L.R.; Hernández-Olmos, V.; Pedro, J.R. New Highly Asymmetric Henry Reaction Catalyzed by CuII and a C1-Symmetric Aminopyridine Ligand, and Its Application to the Synthesis of Miconazole. Chem. A Eur. J. 2008, 14, 4725–4730. [Google Scholar] [CrossRef]
  58. Qiong Ji, Y.; Qi, G.; Judeh, Z.M.A. Catalytic anti-selective asymmetric Henry (nitroaldol) reaction catalyzed by Cu(I)–amine–imine complexes. Tetrahedron Asymmetry 2011, 22, 2065–2070. [Google Scholar] [CrossRef]
  59. Subba Reddy, B.V.; George, J. Enantioselective Henry reaction catalyzed by a copper(II) glucoBOX complex. Tetrahedron Asymmetry 2011, 22, 1169–1175. [Google Scholar] [CrossRef]
  60. Paul, A.; Karmakar, A.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Amide functionalized metal–organic frameworks for diastereoselective nitroaldol (Henry) reaction in aqueous medium. RSC Adv. 2015, 5, 87400–87410. [Google Scholar] [CrossRef]
  61. Karmakar, A.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Zinc metal–organic frameworks: Efficient catalysts for the diastereoselective Henry reaction and transesterification. Dalton Trans. 2014, 43, 7795–7810. [Google Scholar] [CrossRef]
  62. Karmakar, A.; Hazra, S.; Guedes da Silva, M.F.C.; Paul, A.; Pombeiro, A.J.L. Nanoporous lanthanide metal–organic frameworks as efficient heterogeneous catalysts for the Henry reaction. CrystEngComm 2016, 18, 1337–1349. [Google Scholar] [CrossRef]
  63. Christensen, C.; Juhl, K.; Hazell, R.G.; Jørgensen, K.A. Copper-Catalyzed Enantioselective Henry Reactions of α-Keto Esters: An Easy Entry to Optically Active β-Nitro-α-hydroxy Esters and β-Amino-α-hydroxy Esters. J. Org. Chem. 2002, 67, 4875–4881. [Google Scholar] [CrossRef]
  64. Du, D.-M.; Lu, S.-F.; Fang, T.; Xu, J. Asymmetric Henry Reaction Catalyzed by C2-Symmetric Tridentate Bis(oxazoline) and Bis(thiazoline) Complexes: Metal-Controlled Reversal of Enantioselectivity. J. Org. Chem. 2005, 70, 3712–3715. [Google Scholar] [CrossRef]
  65. Santini, C.; Pellei, M.; Lobbia, G.G.; Cingolani, A.; Spagna, R.; Camalli, M. Unprecedented phosphino copper(I) derivatives of tris(pyrazolyl)methanesulfonate ligand co-ordinated to metal in an unusual κ3-N,N′,O fashion. Inorg. Chem. Commun. 2002, 5, 430–433. [Google Scholar] [CrossRef]
  66. Wanke, R.; Smoleński, P.; Guedes da Silva, M.F.C.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. Cu(I) Complexes Bearing the New Sterically Demanding and Coordination Flexible Tris(3-phenyl-1-pyrazolyl)methanesulfonate Ligand and the Water-Soluble Phosphine 1,3,5-Triaza-7-phosphaadamantane or Related Ligands. Inorg. Chem. 2008, 47, 10158–10168. [Google Scholar] [CrossRef]
  67. Silva, T.F.S.; Rocha, B.G.M.; Guedes Da Silva, M.F.C.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. V(iv), Fe(ii), Ni(ii) and Cu(ii) complexes bearing 2,2,2-tris(pyrazol-1-yl)ethyl methanesulfonate: Application as catalysts for the cyclooctane oxidation. New J. Chem. 2016, 40, 528–537. [Google Scholar] [CrossRef]
  68. Jahn, H.A.; Teller, E. Stability of Polyatomic Molecules in Degenerate Electronic States. I. Orbital Degeneracy. Proc. R. Soc. A 1937, 161, 220–235. [Google Scholar]
  69. Bersuker, I.B. Modern Aspects of the Jahn−Teller Effect Theory and Applications To Molecular Problems. Chem. Rev. 2001, 101, 1067–1114. [Google Scholar] [CrossRef]
  70. Murphy, B.; Hathaway, B. The stereochemistry of the copper(II) ion in the solid-state—some recent perspectives linking the Jahn–Teller effect, vibronic coupling, structure correlation analysis, structural pathways and comparative X-ray crystallography. Coord. Chem. Rev. 2003, 243, 237–262. [Google Scholar] [CrossRef]
  71. Boruwa, J.; Gogoi, N.; Saikia, P.P.; Barua, N.C. Catalytic asymmetric Henry reaction. Tetrahedron Asymmetry 2006, 17, 3315–3326. [Google Scholar] [CrossRef]
  72. Qi, N.; Liao, R.-Z.; Yu, J.-G.; Liu, R.-Z. DFT study of the asymmetric nitroaldol (Henry) reaction catalyzed by a dinuclear Zn complex. J. Comput. Chem. 2009, 31, 1376–1384. [Google Scholar] [CrossRef]
  73. Liu, S.; Wolf, C. Asymmetric Nitroaldol Reaction Catalyzed by a C2-Symmetric Bisoxazolidine Ligand. Org. Lett. 2008, 10, 1831–1834. [Google Scholar] [CrossRef]
  74. Pettinari, C.; Marchetti, F.; Cerquetella, A.; Pettinari, R.; Monari, M.; Mac Leod, T.C.O.; Martins, L.M.D.R.S.; Pombeiro, A.J.L. Coordination Chemistry of the (η6-p-Cymene)ruthenium(II) Fragment with Bis-, Tris-, and Tetrakis(pyrazol-1-yl)borate Ligands: Synthesis, Structural, Electrochemical, and Catalytic Diastereoselective Nitroaldol Reaction Studies. Organometallics 2011, 30, 1616–1626. [Google Scholar] [CrossRef]
  75. Shixaliyev, N.Q.; Maharramov, A.M.; Gurbanov, A.V.; Nenajdenko, V.G.; Muzalevskiy, V.M.; Mahmudov, K.T.; Kopylovich, M.N. Zinc(II)-1,3,5-triazapentadienate complex as effective catalyst in Henry reaction. Catal. Today 2013, 217, 76–79. [Google Scholar] [CrossRef]
  76. Karmakar, A.; Martins, L.M.D.R.S.; Hazra, S.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Metal–Organic Frameworks with Pyridyl-Based Isophthalic Acid and Their Catalytic Applications in Microwave Assisted Peroxidative Oxidation of Alcohols and Henry Reaction. Cryst. Growth Des. 2016, 16, 1837–1849. [Google Scholar] [CrossRef]
  77. Mahmudov, K.T.; Kopylovich, M.N.; Haukka, M.; Mahmudova, G.S.; Esmaeila, E.F.; Chyragov, F.M.; Pombeiro, A.J.L. Aqua complex of iron(III) and 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonate: Structure and catalytic activity in Henry reaction. J. Mol. Struct. 2013, 1048, 108–112. [Google Scholar] [CrossRef]
  78. Mahmudov, K.T.; Guedes da Silva, M.F.C.; Sutradhar, M.; Kopylovich, M.N.; Huseynov, F.E.; Shamilov, N.T.; Voronina, A.A.; Buslaeva, T.M.; Pombeiro, A.J.L. Lanthanide derivatives comprising arylhydrazones of β-diketones: Cooperative E/Z isomerization and catalytic activity in nitroaldol reaction. Dalton Trans. 2015, 44, 5602–5610. [Google Scholar] [CrossRef]
  79. Ma, Z.; Sutradhar, M.; Gurbanov, A.V.; Maharramov, A.M.; Aliyeva, R.A.; Aliyeva, F.S.; Bahmanova, F.N.; Mardanova, V.I.; Chyragov, F.M.; Mahmudov, K.T. CoII, NiII and UO2II complexes with β-diketones and their arylhydrazone derivatives: Synthesis, structure and catalytic activity in Henry reaction. Polyhedron 2015, 101, 14–22. [Google Scholar] [CrossRef]
  80. Kopylovich, M.N.; Mac Leod, T.C.O.; Mahmudov, K.T.; Guedes da Silva, M.F.C.; Pombeiro, A.J.L. Zinc(ii) ortho-hydroxyphenylhydrazo-β-diketonate complexes and their catalytic ability towards diastereoselective nitroaldol (Henry) reaction. Dalton Trans. 2011, 40, 5352–5361. [Google Scholar] [CrossRef]
  81. Cwik, A.; Fuchs, A.; Hell, Z.; Clacens, J.-M. Nitroaldol-reaction of aldehydes in the presence of non-activated Mg:Al 2:1 hydrotalcite; a possible new mechanism for the formation of 2-aryl-1,3-dinitropropanes. Tetrahedron 2005, 61, 4015–4021. [Google Scholar] [CrossRef]
  82. Jammi, S.; Ali, M.A.; Sakthivel, S.; Rout, L.; Punniyamurthy, T. Synthesis, Structure, and Application of Self-Assembled Copper(II) Aqua Complex by H-Bonding for Acceleration of the Nitroaldol Reaction on Water. Chem. Asian J. 2009, 4, 314–320. [Google Scholar] [CrossRef]
  83. Reddy, K.R.; Rajasekhar, C.V.; Krishna, G.G. Zinc–Proline Complex: An Efficient, Reusable Catalyst for Direct Nitroaldol Reaction in Aqueous Media. Synth. Commun. 2007, 37, 1971–1976. [Google Scholar] [CrossRef]
  84. Denmark, S.E.; Kesler, B.S.; Moon, Y.C. Inter- and intramolecular [4 + 2] cycloadditions of nitroalkenes with olefins. 2-Nitrostyrenes. J. Org. Chem. 1992, 57, 4912–4924. [Google Scholar] [CrossRef]
  85. Bulbule, V.J.; Deshpande, V.H.; Velu, S.; Sudalai, A.; Sivasankar, S.; Sathe, V.T. Heterogeneous Henry reaction of aldehydes: Diastereoselective synthesis of nitroalcohol derivatives over Mg-Al hydrotalcites. Tetrahedron 1999, 55, 9325–9332. [Google Scholar] [CrossRef]
  86. Bruker. APEX2; SMART and SAINT; Bruker AXS Inc.: Madison, WI, USA, 2012. [Google Scholar]
  87. Bruker. SADABS; Program for Empirical Absorption Correction; Bruker AXS Inc.: Madison, WI, USA, 2001. [Google Scholar]
  88. Altomare, A.; Burla, M.C.; Camalli, M.; Cascarano, G.L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A.G.G.; Polidori, G.; Spagna, R. SIR 97: A new tool for crystal structure determination and refinement. J. Appl. Cryst. 1999, 32, 115–119. [Google Scholar] [CrossRef]
  89. Sheldrick, G.M. IUCr A short history of SHELX. Acta Cryst. Sect. A Found. Cryst. 2008, 64, 112–122. [Google Scholar] [CrossRef]
  90. Farrugia, L.J. WinGX and ORTEP for Windows: An update. J. Appl. Cryst. 2012, 45, 849–854. [Google Scholar] [CrossRef]
Catalysts 09 00611 g001 550
Figure 1. A schematic representation of tris(pyrazolyl)methane compounds.
Figure 1. A schematic representation of tris(pyrazolyl)methane compounds.
Catalysts 09 00611 g001
Catalysts 09 00611 sch001 550
Scheme 1. Synthesis of tris(pyrazolyl)methane sulfonate.
Scheme 1. Synthesis of tris(pyrazolyl)methane sulfonate.
Catalysts 09 00611 sch001
Catalysts 09 00611 sch002 550
Scheme 2. Synthesis of compounds 1–3.
Scheme 2. Synthesis of compounds 1–3.
Catalysts 09 00611 sch002
Catalysts 09 00611 g002 550
Figure 2. ORTEP diagram of 1 with displacement ellipsoids shown at 40% probability level and partial atom labelling scheme. Symmetry operation (i) to generate the equivalent atoms: -x,-y,1-z.
Figure 2. ORTEP diagram of 1 with displacement ellipsoids shown at 40% probability level and partial atom labelling scheme. Symmetry operation (i) to generate the equivalent atoms: -x,-y,1-z.
Catalysts 09 00611 g002
Catalysts 09 00611 g003 550
Figure 3. Effect of the solvent type on the reaction yield, using sole solvents (blue, in the front) and aqueous 1:1 combination (Orange, in the back).
Figure 3. Effect of the solvent type on the reaction yield, using sole solvents (blue, in the front) and aqueous 1:1 combination (Orange, in the back).
Catalysts 09 00611 g003
Table
Table 1. Henry reaction of nitromethane with benzaldehyde catalyzed by 1–3 a.
Table 1. Henry reaction of nitromethane with benzaldehyde catalyzed by 1–3 a.
Catalysts 09 00611 i001
EntryCatalystCat. load b (mol%)Time (h)Temp. (°C)SolventYield c (%)TON d
1152475water5611
2252475water275
3352475water418
415675water275
515875water337
6151275water408
7153675water6814
8154875water7715
9157275water7615
10152460MeOH6112
11152460EtOH235
12152460MeCN71
13152460CH2Cl2<5-
14152460toluene<5-
15152460water4910
16152460water + MeOH5912
17152460water + EtOH479
18152460water + MeCN367
19152460water + CH2Cl2286
20152460water + toluene316
21154823water/MeOH5110
22154860water/MeOH7816
231548100water/MeOH8918
2410.54860water/MeOH1428
25114860water/MeOH3939
26134860water/MeOH5117
27 e151223water>9920
28CuSO4.5H2O52475water122
29Cu(OAc)2.H2O52475water388
30CuCl2.2H2O52475water184
31Cu(NO3)2.2.5H2O52475water265
32152460solvent free--
33--2460water/MeOH--
34(C2H5)3N51223water418
a Reaction conditions: benzaldehyde (0.5 mmol, 1 equiv.), nitromethane (2.5 mmol, 5 equiv.), 2 mL of solvent, with 1:1 ratio in case of mixtures. b Calculated based on benzaldehyde. c Determined by 1H NMR analysis of the products in crude form (see Figure S3). d Moles of 2-nitro-1-phenylethanol per mol of catalyst. e In the presence of 5 mol% triethylamine.
Table
Table 2. Selected data for the Henry coupling of benzaldehyde with nitroethane catalyzed by complex 1 a.
Table 2. Selected data for the Henry coupling of benzaldehyde with nitroethane catalyzed by complex 1 a.
Catalysts 09 00611 i002
EntryTime (h)Temp. (°C)Total yield b (%)Selectivity c (syn:anti)TON d
161002977:235.8
2121004774:269.4
3241006173:2712.2
4481008575:2517.4
5 e24239651:4919.2
a Reaction conditions: benzaldehyde (0.5 mmol, 1 equiv.), nitroethane (2.5 mmol, 5 equiv.), 5 mol% of catalyst 1, 2 mL of water/MeOH (1:1). b Calculated based on benzaldehyde. c Determined by 1H NMR analysis of the products in crude form (see Figure S4). d Moles of 2-nitro-1-phenylpropanol per mol of catalyst. e In the presence of triethylamine (5 mol%).
Table
Table 3. Selected data for the Henry coupling of nitroalkanes with various aldehydes catalyzed by complex 1 a.
Table 3. Selected data for the Henry coupling of nitroalkanes with various aldehydes catalyzed by complex 1 a.
Catalysts 09 00611 i003
EntryXRYield b (%)Selectivity b (syn:anti)TON c
1MeOH53-11
2Me4768:329
3MeH81-16
4Me7472:2815
5HH89-18
6Me8574:2617
7NO2H94-19
8Me8873:2718
9BrH91-18
10Me8670:3017
11ClH89 -18
12Me8671:2917
a Reactions conditions (unless stated otherwise): 100 °C, 48 h in air, aldehyde (0.5 mmol), nitroalkane (2.5 mmol), 5 mol% of 1, 2 mL of water and MeOH (1:1). b Determined by 1H NMR analysis of crude products. c Moles of β-nitro alcohol per mol of catalyst.

Share and Cite

MDPI and ACS Style

Mahmoud, A.G.; Martins, L.M.D.R.S.; Silva, M.F.C.G.d.; Pombeiro, A.J.L. Hydrosoluble Complexes Bearing Tris(pyrazolyl)methane Sulfonate Ligand: Synthesis, Characterization and Catalytic Activity for Henry Reaction. Catalysts 2019, 9, 611. https://doi.org/10.3390/catal9070611

AMA Style

Mahmoud AG, Martins LMDRS, Silva MFCGd, Pombeiro AJL. Hydrosoluble Complexes Bearing Tris(pyrazolyl)methane Sulfonate Ligand: Synthesis, Characterization and Catalytic Activity for Henry Reaction. Catalysts. 2019; 9(7):611. https://doi.org/10.3390/catal9070611

Chicago/Turabian Style

Mahmoud, Abdallah G., Luísa M. D. R. S. Martins, M. Fátima C. Guedes da Silva, and Armando J. L. Pombeiro. 2019. "Hydrosoluble Complexes Bearing Tris(pyrazolyl)methane Sulfonate Ligand: Synthesis, Characterization and Catalytic Activity for Henry Reaction" Catalysts 9, no. 7: 611. https://doi.org/10.3390/catal9070611

APA Style

Mahmoud, A. G., Martins, L. M. D. R. S., Silva, M. F. C. G. d., & Pombeiro, A. J. L. (2019). Hydrosoluble Complexes Bearing Tris(pyrazolyl)methane Sulfonate Ligand: Synthesis, Characterization and Catalytic Activity for Henry Reaction. Catalysts, 9(7), 611. https://doi.org/10.3390/catal9070611

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop