Oxidative cleavage of nitroalkenes with hydrogen peroxide in environmentally acceptable solvents

Article abstract of DOI:10.1246/cl.2007.472

Hydrogen peroxide serves as an efficient oxidant for the nitroalkene C=C bond cleavage to aldehydes in ionic liquids. Copyright

Full text of DOI:10.1246/cl.2007.472

472
Chemistry Letters Vol.36, No.3 (2007)
Oxidative Cleavage of Nitroalkenes with Hydrogen Peroxide
in Environmentally Acceptable Solvents
Olga Bortolini,Ã1 Antonio De Nino,1 Marco Fogagnolo,2 Giancarlo Fantin,2
Loredana Mariuolo,1 and Amedeo Tocci1
1
`
Dipartimento di Chimica Universita della Calabria, Via Bucci 12 C, 87036 Rende, Italy
Dipartimento di Chimica, Universita di Ferrara, Via Borsari 46, 44100 Ferrara, Italy
2
`
(Received January 11, 2007; CL-070040; E-mail: o.bortolini@unical.it)
Hydrogen peroxide serves as an efficient oxidant for the
nitroalkene C=C bond cleavage to aldehydes in ionic liquids.
epoxidation protocol to electron-deficient olefins bearing nitro
substituents, however, evidenced both different reactivity and
dissimilar product selectivity with respect to conventional condi-
tions.12 The epoxidation of 2-nitro-para-methylstyrene, 2-(2-
nitrovinyl)thiophene and 2-(2-nitrovinyl)furan, in fact, afforded
almost exclusively the related carbon–carbon bond cleavage
products i.e. para-methylbenzaldehyde, 2-thiophenecarboxalde-
hyde, 2-furaldehyde according to eq 1. No over-oxidation to car-
boxylic acid derivatives is observed under the conditions adopt-
ed for this oxidation. The possibility to observe 2-nitrostyrene
C=C bond cleavage using H2O2/OHÀ was reported by Newman
and Angier.13 Substitution on the carbon bearing the nitro sub-
stituent appeared a fundamental requisite to avoid cleavage in
favour of the epoxidation reaction. Our conditions, however,
did not conform to this requisite and C=C bond cleavage is ob-
served also with ꢁ-substituted substrates as nitrocyclohexene
(Entry 7), ꢁ-ethyl- and ꢁ-pentyl-nitrostyrene (Entries 8 and 9).
The detection of hexane-1,6-dial and benzaldehyde plus propa-
nal or hexanal in the latter cases was particularly important in
order to elucidate the mechanism of this reaction. Cleavage of
nitroalkenes proceeds via epoxidation, followed by rupture of
the carbon–carbon bond according to eq 2. Support to this
assumption may be found in the detection of ꢁ-ethyl- and ꢁ-
pentyl-nitrostyrene epoxides in the initial moments of the epox-
idations and in an independent experiment carried out on nitro-
styrene epoxide, prepared using a different oxidation proce-
dure.14 When dissolved in bmim(TfO), in the presence of the
oxidant H2O2/OHÀ, the nitrostyrene epoxide is quantitatively
converted into the corresponding benzaldehyde in few minutes.
No over-oxidation or additional products, for example benzoic
acid or diol, are detected. On the other hand, relatively small
amounts of over-oxidation products i.e. propanoic acid and
hexanoic acid originating from propanal and hexanal are detect-
ed in the oxidation of the ꢁ-substituted-nitrostyrenes of Entries 8
and 9.
Oxidative cleavage of carbon–carbon double bonds is an
important transformation in synthetic organic chemistry.1
Ozonolysis2 or oxometal reagents3 in combination with oxygen
donors as NaIO4 are frequently used for this purpose. However,
because of the known drawbacks of these reagents, catalytic
oxidations using eco-friendly oxidants4 like hydrogen peroxide5
or molecular oxygen6 have attracted increasing attention. In
this frame, we have recently re-evaluated the epoxidation of
electron-deficient olefins with alkaline hydrogen peroxide
(Weitz–Scheffer reaction) in ionic liquids,7 a novel alternative
to traditional volatile and carcinogenic solvents,8 that allow easy
product recovery, solvent recycling and, in some cases, different
product selectivity.
O
H
NO2
R'
H2O2/OH-
bmimOTf
R
+
R
H
O
R'
R'
(1)
O
H2O2/OH-
bmimOTf
NO2
NO2
R
R
R'
C-C bond cleavage
H
O
R'
(2)
+
Work is in progress to optimize the conversion of nitro
derivatives, including saturated substrates, to aldehydes and
ketones with low cost and eco-friendly oxidants in ionic
liquids.
R
O
H
As described in our previous publications7 the epoxidation
of several ꢀ; ꢁ-unsaturated cyclic ketones with basic aqueous
solutions of H2O2 in bmim(TfÀO) (bmim = 1-butyl-3-methyl-
9
imidazolium, TfOÀ = CF3SO3
)
at room temperature pro-
References and Notes
ceeds rapidly with formation of the corresponding epoxides in
97–99% yield; see for example Entry 1 of Table 1. The presence
of substituents on the molecular framework do not affect the
course of the epoxidation, including that of base-sensitive sub-
strates as the Hagemann’s ester10 (Entry 2). The epoxidation
of acyclic ꢀ; ꢁ-unsaturated ketones11 as chalcone may be satis-
factory carried out under similar conditions with excellent
conversion and product yield (Entry 3). The extension of this
1
D. G. Lee, T. Chen, in Comprehensive Organic Synthesis,
ed. by B. M. Trost, I. Fleming, S. V. Ley, Pergamon Oxford,
1991, p. 541.
P. S. Bayley, Ozonation in Organic Chemistry, Academic
Press, New York, 1978, Vol. 1.
a) C.-M. Ho, W.-Y. Yu, C.-M. Che, Angew. Chem., Int. Ed.
2004, 43, 3303. b) D. Yang, C. Zhang, J. Org. Chem. 2001,
66, 4814, and references.
2
3
Copyright Ó 2007 The Chemical Society of Japan

Chemistry Letters Vol.36, No.3 (2007)
473
Table 1. Epoxidation and C=C bond cleavage of electron-deficient olefins with H2O2/OHÀ in bmim(OTf) at 25 ꢀC: [substrate]:
[H2O2]:[OHÀ] = 1:3:2; for details see Supporting Information
Entry
Alkene
Product
Time
/h
Yielda
/%
O
O
1
2
0.1
0.5
97
98
O
O
O
O
COOEt
COOEt
O
O
O
3
3
99
CHO
NO2
4
5
6
0.5
1
98
84
94
CH3
CH3
NO2
CHO
CHO
S
S
NO2
1
O
O
NO2
CHO
OHC
7
8
9
72
16
16
42
NO2
CHO
H
O
C
O
C
70b,c
CH2CH3
CH2CH3
+
HO
CH2CH3
NO2
CH2(CH2)3CH3
b
CHO
H
O
C
O
75b,c
C
+
CH2(CH2)3CH3
HO
CH2(CH2)3CH3
aBased on GC analysis. Calculated on the recovered Ph–CHO. No benzoic acid was detected.
c
4
5
R. Noyori, M. Aoki, K. Sato, Chem. Commun. 2003, 1977.
a) W. A. Herrmann, T. Weskamp, J. P. Zoller, R. W. Fischer,
J. Mol. Catal. A: Chem. 2000, 153, 49. b) C. D. Brooks,
L. C. Huang, M. McCarron, R. A. W. Johnstone, Chem.
Commun. 1999, 37. c) E. Antonelli, R. D’Aloisio, M.
Gambaro, T. Fiorani, C. Venturello, J. Org. Chem. 1998,
63, 7190. d) M. Shimizu, H. Orita, K. Suzuki, T. Hayakawa,
S. Hamakawa, K. Takehira, J. Mol. Catal. A: Chem.
1996, 114, 217. e) B. M. Choudary, P. N. Reddy, J. Mol.
Catal. A: Chem. 1995, 103, L1.
a) Y. Hayashi, M. Takeda, Y. Miyamoto, M. Shoji, Chem.
´
Lett. 2002, 414. b) X. Baucherel, J. Uziel, S. Juge, J. Org.
Chem. 2001, 66, 4504.
a) O. Bortolini, V. Conte, C. Chiappe, G. Fantin, M.
Fogagnolo, S. Maietti, Green Chem. 2002, 4, 94. b) O.
Bortolini, S. Campestrini, V. Conte, M. Fogagnolo, G.
Fantin, S. Maietti, Eur. J. Org. Chem. 2003, 4804.
T. Welton, Coord. Chem. Rev. 2004, 248, 2459.
9
For the synthesis of bmim(TfO) see: P. Bonhote, A.-P. Dias,
N. Papageorgiou, K. Kalyanasundaram, M. Gratzel, Inorg.
Chem. 1996, 35, 1168.
10 R. R. Crenshaw, G. M. Luke, T. A. Jenks, G. Bialy, M. E.
Bierwagen, J. Med. Chem. 1972, 15, 1162.
11 B. Wang, Y.-R. Kang, L.-M. Yang, J.-S. Suo, J. Mol. Catal.
A: Chem. 2003, 203, 29.
12 N. A. Sokolov, Y. G. Chernov, Y. V. Glazkov, J. Org. Chem.
USSR 1972, 8, 2371.
13 H. Newman, R. B. Angier, J. Chem. Soc. D 1969, 369.
14 Nitrostyrene epoxide was prepared by oxidation with tri-
fluoromethyl methyl dioxirane (TFD) in CH2Cl2 at 0 ꢀC,
see Supporting Information available electronical on the
Journal-web site; http://www.csj.jp/journals/chem-lett/
index.html.
15 R. Ballini, M. Petrini, Tetrahedron 2004, 60, 1017.
16 C. Narayana, N. K. Reddy, G. W. Kabalka, Synth. Commun.
1992, 22, 2587.
6
7
8
Published on the web (Advance View) February 24, 2007; doi:10.1246/cl.2007.472