Nickel(II) catalyzed oxidation of aldehyde derivatives to their carboxylic acid or ester analogs

Article abstract of DOI:10.1007/s11164-012-0844-y

Diverse aromatic, aliphatic and conjugated aldehydes were converted to the corresponding carboxylic acid or methyl ester derivatives with 30 % H ₂O₂ as the oxidant in the presence of a catalytic amount of nickel(II) complex as precursor. Ni(II) complex was prepared from the reaction of methyl 2-{3-[(E)-4-oxopent-2-en-2-ylamino]propylamino}cyclopent-1- enecarbodithioate as a tetra-dentate ligand with Ni(II) acetate in 60 % yield and was tested for its catalytic activity in the oxidation reaction. The prepared complex was characterized on the basis of ¹H NMR, FT-IR, MASS, and CHN analysis. Aldehydes were oxidized to their corresponding carboxylic acid in acetonitrile as solvent and were converted to methyl esters in methanol as solvent. For all substrates, a considerable rate enhancement was observed. The present methodology offers several advantages such as applicability to a wide range of aldehydes, convenient work-up, mild reaction conditions, and good yields and reasonable time of the reactions. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s11164-012-0844-y

Res Chem Intermed
DOI 10.1007/s11164-012-0844-y
Nickel(II) catalyzed oxidation of aldehyde derivatives
to their carboxylic acid or ester analogs
•
Hadi Esfandiari Saeed Jameh-bozorghi
•
•
Sheida Esmaielzadeh
Mohammad Reza Mohammad Shafiee
Majid Ghashang
•
Received: 26 June 2012 / Accepted: 29 September 2012
Ó Springer Science+Business Media Dordrecht 2012
Abstract Diverse aromatic, aliphatic and conjugated aldehydes were converted to
the corresponding carboxylic acid or methyl ester derivatives with 30 % H2O2 as the
oxidant in the presence of a catalytic amount of nickel(II) complex as precursor.
Ni(II) complex was prepared from the reaction of methyl 2-{3-[(E)-4-oxopent-2-en-
2-ylamino]propylamino}cyclopent-1-enecarbodithioate as a tetra-dentate ligand
with Ni(II) acetate in 60 % yield and was tested for its catalytic activity in the
1
oxidation reaction. The prepared complex was characterized on the basis of H
NMR, FT–IR, MASS, and CHN analysis. Aldehydes were oxidized to their cor-
responding carboxylic acid in acetonitrile as solvent and were converted to methyl
esters in methanol as solvent. For all substrates, a considerable rate enhancement
was observed. The present methodology offers several advantages such as appli-
cability to a wide range of aldehydes, convenient work-up, mild reaction conditions,
and good yields and reasonable time of the reactions.
Keywords Oxidation Á Aldehyde Á Acid Á Methyl ester Á H2O2 Á Ni(II) complex
H. Esfandiari (&)
Faculty of Science, Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran
e-mail: hesfandiari864@gmail.com
S. Jameh-bozorghi
Faculty of Science, Department of Chemistry, Touyserkan Branch, Islamic Azad University,
Touyserkan, Iran
S. Esmaielzadeh
Department of Chemistry, Darab Branch, Islamic Azad University, Darab, Iran
M. R. M. Shafiee Á M. Ghashang
Department of Chemistry, Faculty of Sciences, Najafabad Branch, Islamic Azad University,
Najafabad, Esfahan, Iran
123

H. Esfandiari et al.
Introduction
An acceptable demand of organic chemists is to use cheap, non-toxic, and
environmentally friendly reactants, including reducing agents, oxidants, etc., in
organic transformations. In this context, oxidation reactions and especially oxidation
of aldehydes to carboxylic acids is a fundamental chemical transformation in organic
chemistry [1–3]. The oxidation of aldehydes to carboxylic acid with various oxidants
has been intensively studied during recent years [3–11]. One of the best of these
oxidants is aqueous hydrogen peroxide that has some advantages, such as cheapness,
ease of handling, and having a high percentage of available oxygen. Unluckily,
hydrogen peroxide has a high activation barrier for its reaction with organic substrates
[12]. To overcome this, a number of catalytic procedures for H2O2 oxidation have been
developed [13–25].
To expand this number, the present paper deals with the use of methyl-2-{N-[4-
(pent-2-enolato)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarbox-
ylate Ni(II) (A) as catalyst in the oxidation of aldehydes to corresponding carboxylic
acids in acetonitrile as solvent (Scheme 1).
Results and discussion
Methyl 2-{3-[(E)-4-oxopent-2-en-2-ylamino]propylamino}cyclopent-1-enecarbo-
dithioate as a ligand for Ni(II) and their corresponding complex (A) was synthesized
with high yields according to previously published literature procedures [25–28].
1
The prepared complex was characterized on the basis of H NMR, FT–IR, MASS,
and CHN analysis.
The distinctive peaks in the 1H NMR spectra of the ligand and the Ni(II) complex
are presented in Table 1. In the 1H NMR spectra of the free ligand, the OH signal was
seen at 12.41 ppm and SH signal at 10.93 ppm, and these disappear in the Ni(II)
complex, indicating that the OH and SH groups have been bonded to the Ni(II) ions
H3C
CH3
N
N
O
S
Ni
(A)
SCH3
(R)Ar COOH
(R)Ar CHO
(R)Ar CHO
H2O2;60 oC; CH3CN
(A)
(R)Ar COOCH3
H2O2;60 oC; CH3OH
Scheme 1 Oxidation of aldehydes to carboxylic acids or esters over A as catalyst
123

Ni(II) catalyzed oxidation of aldehyde derivatives
after de-protonation (Table 1). The methyl protons connected to the sulfur atom of the
ligand (2.58 ppm) are shifted to higher fields in the Ni(II) complex (2.64 ppm). The
CH2 protons connected to nitrogen atom (–CH2–N=C) appeared at 3.48–3.55 ppm in
the free ligand, shifting to a higher field (3.57–3.74 ppm), confirming the coordination
of the Ni(II) to nitrogen atoms (Table 1).
The appearance of the strong vibration in the region 440–550 cm-1 in the FT–IR
spectrum confirms the presence of Ni–N, Ni–O, and Ni–S bonds [29, 30].
The catalytic activity of A has been studied in the mild oxidation of various
aromatic and aliphatic aldehydes (Scheme 1).
In an initial screening, the oxidation of 4-chlorobenzaldehyde in acetonitrile as
solvent at 60 °C has been investigated (Table 2) in the presence of various kind of
Ni(II) salts. Reaction with NiSO4, NiO, Ni(NH3)6Cl2 and Ni(en)2Cl2 yielded less
than A (Table 2), indicating that A is the specific catalyst for the oxidation of
aldehydes. We therefore proceeded with the oxidation of 4-chlorobenzaldehyde to
the corresponding carboxylic acids using A as catalyst (Table 2). At room
temperature, the conversion of 4-chlorobenzaldehyde to the product was found to be
low (60 %). The results revealed that the presence of H2O2 as co-catalyst is required
for the oxidation reaction.
Table 1 1H NMR data (250 MHz; ppm; CDCl3 as solvent) of the ligand and Ni(II) complex
OH
SH
SCH3
CH(sp2)
(–CH2–N=C
Free ligand
12.41
–
10.93
–
2.58
2.64
7.67
7.26
3.48–3.55
3.57–3.74
Ni(II) complex
Table 2 Optimization of the reaction conditions in the synthesis of 4-Chlorobenzoic acid
Entry
Catalyst (mmol)
T (°C)
Solvent (5 mL)
Yield (%)a
1
NiSO4 (0.13)
NiO (0.13)
Ni(NH3)6Cl2 (0.13)
Ni(en)2Cl2 (0.13)
A (0.13)
60
60
60
60
60
60
25
60
35
40
60
60
60
60
60
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
n-Hexane
CH2Cl2
Et2O
70
2
50
3
68
4
30
5
87
6
A (0.13)
10 (without H2O2)
7
A (0.13)
50
64
65
71
85
85
89
58
56
8
A (0.13)
9
A (0.13)
10
11
12
13
14
15
a
A (0.13)
A (0.13)
EtOAc
A (0.26)
CH3CN
CH3CN
CH3CN
CH3CN
A (0.07)
A (0.03)
A (0.01)
Isolated yields, reaction time: 3 h
123

H. Esfandiari et al.
In order to find the optimal reaction medium, the effect of various common
organic solvents was investigated, from which it was deduced that acetonitrile
appears to be the most favorable (Table 2, entry 5). Next, the oxidation reaction was
carried out in the presence of 0.26, 0.13, 0.07, 0.03, and 0.01 mmol of A with the
other parameters kept constant. Among the various amounts of the catalyst tested,
the oxidation reaction was best catalyzed by 0.07 mmol (Table 2, entry 13).
Table 3 Synthesis of carboxylic acid derivatives using A as catalyst (Scheme 1)
Entry
Aldehyde
Time (h)
Yield (%)a
1
Benzaldehyde
2
3
4
4
3
2
3
2
3
3
3
4
4
5
3
5
5
90
89
80
84
86
85
79
86
77
88
89
89
87
84
76
70
85
2
4-Chlorobenzaldehyde
2-Chlorobenzaldehyde
2,4-Dichlorobenzaldehyde
2,4-Dimethoxybenzaldehyde
4-Methoxybenzaldehyde
2-Methoxybenzaldehyde
4-Methylbenzaldehyde
2-Methylbenzaldehyde
4-Bromobenzaldehyde
3-Bromobenzaldehyde
4-Nitrobenzaldehyde
3-Nitrobenzaldehyde
2-Nitrobenzaldehyde
Furfural
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
a
Butyraldehyde
Cyclohexanecarbaldehyde
Isolated yields
Table 4 Oxidative esterification of aldehydes to corresponding methyl esters using A as catalyst
(Scheme 1)
Entry
Aldehyde
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
9
a
Benzaldehyde
4
92
91
88
87
89
81
86
90
72
4-Chlorobenzaldehyde
4-Methoxybenzaldehyde
2-Methoxybenzaldehyde
4-Methylbenzaldehyde
4-Bromobenzaldehyde
3-Bromobenzaldehyde
4-Nitrobenzaldehyde
Furfural
4.5
2.5
3
2.5
3.5
4.5
6
3.5
Isolated yields
123

Ni(II) catalyzed oxidation of aldehyde derivatives
Using these optimized reaction conditions, the scope and efficiency of these
procedures were explored for the oxidation of various aromatic and aliphatic aldehydes.
Generally, all the oxidation reactions proceeded well and afforded the desired products
(Table 3, entries 1–17) in good to excellent yields. As shown in Table 3, the reaction
was successfully compatible with a variety of aryl aldehydes having electron-donating
and electron-withdrawing substituents. Aromatic aldehydes substituted with electron-
withdrawing groups react slowly (Table 3, entries 12–14). The results show that
aliphaticaldehydescanbesuccessfullyoxidizedingoodyields(Table 3, entries16–17).
Under the same optimized reaction conditions (Table 2) and using methanol as
solvent, the aldehydes can all be oxidized to the corresponding methyl esters in
excellent yields (Scheme 1). The results are summarized in Table 4.
Conclusion
In conclusion, a Ni(II) complex catalyzed one-pot reaction sequence for the
oxidation of aldehydes to the corresponding carboxylic acid or methyl ester has
1
been developed. The prepared catalyst was characterized using H NMR, FT–IR,
MASS, and CHN analysis. Various kinds of aromatic and aliphatic aldehydes were
investigated and the desired products were obtained in high yields. H2O2 was used
as oxidant. The present method represents a simple and highly efficient method for
the oxidation of aldehydes to their carboxylic acid or methyl ester analogs under
mild conditions.
Experimental
Material and instrumentation
All reagents were purchased from Merck and Aldrich and were used as received. All
yields refer to isolated products after purification. The NMR spectra were recorded
on a Bruker Avance DPX 400 MHz instrument. The spectra were measured in
CDCl3 relative to TMS (0.00 ppm). IR spectra were recorded on a Perkine Elmer
781 spectrophotometer. TLC was performed on silica gel polygram SIL G/UV 254
plates.
Preparation of A
Methyl 2-{3-[(E)-4-oxopent-2-en-2-ylamino]propylamino}cyclopent-1-enecarbo-
dithioate was prepared by the known reported procedures [29–31]. Complex
preparation: using a solution of the appropriate ligand (0.1 mmol) in 10 mL of
chloroform/methanol 2:1 (V:V) was added Ni(II) acetate (0.1 mmol) dissolved in
10 mL of methanol, and the solution was stirred for 15 min. After that time, the
reaction mixture was allowed to stand at room temperature for 24 h. Finally, the
crude product was filtered and recrystallized from acetonitrile/methanol 1:1 (V:V)
to afford the pure product. Spectroscopic data for A are as follows:
123

H. Esfandiari et al.
1
Yield: 63 %, m.p.: 233 °C; H NMR (d, ppm, 250 MHz, CDCl3): 1.77 (3H, s,
CH3), 1.25–2.03 (5H,m), 2.44–2.61 (4H, m), 2.64 (3H, s, SCH3), 3.57–3.74 (4H, m),
7.26 (1H (sp2), s); IR (KBr, cm-1): 440–550 (m
Ni–S?mNi–N?mNi–O), 750 (mC–S), 1,010
(mC–S?mC–N), 1,284 (mC–O), 1,463 (mC=C), 1,558, 1,595 (mC=N), 2,900 (mC–H); MS
Spectra: m/z (%) = 356[M ? 1]?, 355[M]?, 309, 294, 279, 189, 111, 97, 57;
Elemental Anal.: % Found (% Calc): C14H20N2OS2Ni, C: 47.47 (47.35); H: 5.77
(5.68); N: 7.95 (7.89); S: 18.14 (18.06).
Typical procedure for the preparation of carboxylic acids
A solution of 4-chlorobenzaldehyde (1 mmol) and A (0.07 mmol) in 5 mL of
CH3CN was added to aqueous H2O2 (0.5 mL, 30 % in water). The resulting reaction
mixture was stirred at 60 °C for the appropriate time (Table 3). After completion of
the reaction, as indicated by TLC, the solvent was evaporated and, to obtain the
crude reaction mixture, NaHCO3 (10 %) was added and then the reaction mixture
was extracted with ethyl acetate. The aqueous layer was acidified to pH 2.0 using
2 N HCl and extracted with ethyl acetate. The organic layer was concentrated and
purified by plate chromatography (n-hexane/ethyl acetate 95/5) to give the pure
product (Table 3).
Typical procedure for the preparation of methyl esters
To a solution of 4-chlorobenzaldehyde (1 mmol) and A (0.07 mmol) in 5 mL of
CH3OH was added aqueous H2O2 (0.5 mL, 30 % in water). The resulting reaction
mixture was stirred at 60 °C for the appropriate time (Table 4). After completion of
the reaction, as indicated by TLC, the solvent was evaporated and the resulting
crude reaction mixture was purified by plate chromatography (n-hexane/ethyl
acetate 95/5) to give the pure product (Table 4).
Selected data
Methyl benzoate (Table 4, entry 1): 1H NMR (200 MHz, CDCl3): d = 8.05 (d, 2H,
J = 7.4 Hz), 7.46–7.58 (m, 3H) 3.91 (s, 3H).
Methyl 4-chlorobenzoate (Table 4, entry 2): 1H NMR (200 MHz, CDCl3):
d = 7.95 (d, 2H, J = 8.5 Hz), 7.41 (d, 2H, J = 8.5 Hz), 3.90 (s, 3H).
Acknowledgment The authors are indebted to the Najafabad Branch, Islamic Azad University for
financial support of this research.
References
1. G.J. Hollingworth, in Comprehensive Organic Functional Group Transformations, vol. 5, ed. by
A.R. Katritzky, O. Meth-Cohn, C.W. Rees, G. Pattenden (Elsevier, Oxford, 1995)
2. M. Hudlicky, Oxidations in Organic Chemistry, ACS Monograph, vol. 186 (American Chemical
Society, Washington DC, 1990)
3. R.C. Larock, Comprehensive Organic Transformations: A Guide to Functional Group Preparations,
2nd edn. (Wiley, New York, 1999)
123

Ni(II) catalyzed oxidation of aldehyde derivatives
4. R.T. Benjamin, M. Sivakumar, G.O. Hollist, B. Borhan, Org. Lett. 5, 1031 (2003)
5. S.O. Nwaukwa, P.M. Keehn, Tetrahedron Lett. 23, 3131 (1982)
6. B. Ganem, R.P. Heggs, A.J. Biloski, D.R. Schwartz, Tetrahedron Lett. 21, 685 (1980)
7. T. Yamada, O. Rhode, T. Takai, T. Mukaiyama, Chem. Lett. 5 (1991)
8. A.N. Kharata, P. Pendleton, A. Badalyan, M. Abedini, M.M. Amini, J. Mol. Catal. A Chem. 175, 277
(2001)
9. S. Biella, L. Prati, M. Rossi, J. Mol. Catal. A Chem. 197, 207 (2003)
10. J.M. Grill, J.W. Ogle, S.A. Miller, J. Org. Chem. 71, 9291 (2006)
11. J.K. Joseph, S.L. Jain, J.B. Sain, Catal. Commun. 8, 83 (2007)
12. M. Lim, C.M. Yoon, G. An, H. Rhee, Tetrahedron Lett. 48, 3835 (2007)
13. E. Spath, M. Pailer, M. Schmid, Chem. Ber. 74, 1552 (1941)
14. J.H. Birkinshaw, H. Raistrick, D.J. Ross, C.E. Stickings, Biochem. J. 5, 610 (1952)
15. K. Sato, M. Hyodo, J. Takagi, M. Aoki, R. Noyori, Tetrahedron Lett. 41, 1439 (2000)
16. R. Balicki, Synth. Commun. 31, 2195 (2001)
17. R.H. Dodd, M. Le Hyaric, Synthesis 3, 295 (1993)
18. E. Delcanale, F. Montanari, J. Org. Chem. 51, 567 (1986)
19. J.K. Choi, Y.K. Chang, S.Y. Hong, Tetrahedron Lett. 29, 1967 (1988)
20. H. Heaney, A.J. Newbold, Tetrahedron Lett. 42, 6607 (2001)
21. B. Bhatia, T. Punniyamurthy, J. Iqbal, J. Org. Chem. 58, 5518 (1993)
22. H. Heaney, Top. Curr. Chem. 1, 164 (1993)
23. M. Brzaszcz, K. Kloc, M. Maposah, J. Mlochowski, Synth. Commun. 30, 4425 (2000)
24. G.J. Brink, J.M. Vis, I.W.C.E. Arends, R.A. Sheldon, Tetrahedron 58, 3977 (2002)
25. R. Bernini, A. Coratti, G. Provenzano, G. Fabrizi, D. Tofani, Tetrahedron 61, 1821 (2005)
26. K. Nag, D.S. Joardar, Inorg. Chim. Acta 14, 133 (1975)
27. E. Pereira, L. Gomes, B. de Castro, Inorg. Chim. Acta 271, 83 (1998)
28. M. Asadi, K. Mohammadi, S. Esmaielzadeh, B. Etemadi, H. Kun Fun, Polyhedron 28, 1409 (2009)
29. M. Asadi, K. Mohammadi, S. Esmaielzadeh, B. Etemadi, H. Kun Fun, Inorg. Chim. Acta 362, 4913
(2009)
30. T.A. Khan, Synth. React. Inorg. Met. Org. Chem. 31, 1023 (2001)
31. K. Nakamoto, Raman and Infrared Spectra of Inorganic and Coordination Compounds, 4th edn.
(Wiley, New York, 1986)
123