Iron catalysed nitrosation of olefins to oximes

Article abstract of DOI:10.1039/c3dt51764k

Fe(BF₄)₂·6H₂O/2,6- pyridinedicarboxylic acid catalysed nitrosation of a wide variety of substituted styrenes has been developed in the presence of t-BuONO/NaBH₄ under H₂ pressure (10 bar) in MeOH-H₂O (5 : 1) to afford corresponding oximes in good to excellent yields.

Full text of DOI:10.1039/c3dt51764k

Dalton
Transactions
View Article Online
View Journal | View Issue
COMMUNICATION
Iron catalysed nitrosation of olefins to oximes†
Ritwika Ray, Abhishek Dutta Chowdhury, Debabrata Maiti* and
Goutam Kumar Lahiri*
Cite this: Dalton Trans., 2014, 43, 38
Received 1st July 2013,
Accepted 14th October 2013
DOI: 10.1039/c3dt51764k
www.rsc.org/dalton
Fe(BF4)2·6H2O/2,6-pyridinedicarboxylic acid catalysed nitrosation
of a wide variety of substituted styrenes has been developed in the
presence of t-BuONO/NaBH4 under H2 pressure (10 bar) in
MeOH–H2O (5 : 1) to afford corresponding oximes in good to
excellent yields.
The Beckmann rearrangement of cyclohexanone oxime to
ε-caprolactum is an industrially important reaction for the syn-
thesis of Nylon-6.1 Moreover, oximes can be easily reduced to
amines,2 which are further used in the manufacturing of dyes,
plastics, synthetic fibres and pharmaceuticals. Oximes are
used as anti-skinning agents in paint and blocking agents in
the polymer industry.3 Biological activities including anti-aller-
gic and anti-inflammatory behaviours of oximes have also
been demonstrated.4 Recently, Ley and Bertram have further
revealed that oximes and oxime-ethers of hydroxylated benz-
aldehydes and acetophenones are powerful anti-oxidants.5
Thus, owing to the extensive utility of oximes, both in industry
and biology, development of sustainable and novel methods
for their synthesis continues to be an active area of research.6
Nitrosation of olefin feedstock in the presence of nitric oxide
or alkyl nitrites is one of the convenient approaches for produ-
cing oximes. However, catalytic nitrosation of olefins in the
presence of various reductants is rare. Only a few reports invol-
ving cobalt catalysed oxime formation are known in the litera-
ture so far.7 Environmentally benign iron mediated oxime
synthesis is limited to the only example reported by Beller
et al. where iron(II)-phthalocyanine was used as the active cata-
lytic species.8 Herein we demonstrate a simple and convenient
method of Fe(BF4)2·6H2O/2,6-pyridinedicarboxylic acid (dipic)
catalysed synthesis of oximes (2) from styrene derivatives (1) in
the presence of cheap and readily available tertiary-butylnitrite
(t-BuONO) and sodium borohydride (NaBH4) (Scheme 1).9
Scheme 1 An outline for the catalytic transformation of 1 to 2.
During our initial investigation, the reaction of styrene with
t-BuONO/NaBH4 in the presence of Fe(BF4)2·6H2O/dipic was
chosen as the model system. Optimisation of the critical reac-
tion parameters by employing an array of solvents establishes
MeOH–H2O (5 : 1) as the best combination (Table 1, entry 3).
The use of only MeOH as the solvent results in appreciably
lower yield of the desired product (Table 1, entry 5). Notably,
addition of water (1 mL) along with MeOH (5 mL) leads to the
product formation in excellent yield (Table 1, entry 3). On the
other hand, EtOH–H2O (5 : 1) as a solvent system produces
acetophenone oxime in 65% yield (GC yield) under the identi-
cal reaction conditions (Table 1, entry 8). However, the selec-
tive use of EtOH improves the yield to a small extent (Table 1,
entry 10), but it is reasonably low compared to the MeOH–H2O
(5 : 1) solvent system, which indeed has prompted us to restrict
the present investigations in MeOH–H2O (5 : 1).
It should also be noted that the yield of the oxime
decreased considerably when the same reaction was carried
out for longer time and with higher catalyst loading. Therefore,
it is presumed that oximes being slowly reduced by BH4−, a
prolonged reaction time led to the decomposition of the pro-
ducts.7d Lowering of the yield can further be attributed to the
probable side reactions leading to the formation of nitroso-
alkanes, nitrosohydroxylamines, azo compounds and N-nitroso-
amine oxides.10 However, these complex nitrogen compounds
could not be detected since such compounds get adsorbed on
the silica gel column during the isolation of the products.7d
Other hydrogenation side-products, resulting from the reduction
Department of Chemistry, Indian Institute of Technology Bombay, Powai,
Mumbai 400076, India. E-mail: lahiri@chem.iitb.ac.in, dmaiti@chem.iitb.ac.in
†Electronic supplementary information (ESI) available: General procedure,
characterization data and 1H and 13C-NMR spectra of 2a–2u. See DOI: 10.1039/
c3dt51764k
38 | Dalton Trans., 2014, 43, 38–41
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Communication
Table 1 Iron catalysed nitrosation of olefins in various solventsa
Table 2 Catalytic nitrosation of olefinsa
Catalystb
Conversion (%)
Yieldc (%)
Entry
Solvent
Conversionb (%)
Yieldc (%)
Entry
1
Toluene
0
>90
>99
80
90
10
85
90
80
85
0
1
2
3
4
5
6
7
8
FeCl3·6H2O/pic
FeCl3·6H2O/dipic
FeSO4·7H2O/pic
FeSO4·7H2O/dipic
Fe(ClO4)2·6H2O/pic
Fe(ClO4)2·6H2O/dipic
Fe(BF4)2·6H2O/pic
Fe(BF4)2·6H2O/bipy
Fe(BF4)2·6H2O/dppf
Fe(BF4)2·6H2O/trpy
Fe(BF4)2·6H2O/dipic
Fe(Pc)
75
60
65
75
25
80
90
50
85
88
>99
>90
70
75
10
75
45
40
45
40
14
45
65
35
70
69
99 (90)
80
20
25
2
2d
3
MeOH–H2O (5 : 1)
MeOH–H2O (5 : 1)
MeOH
82 (75)
99 (90)
60
65
5
60
65
70
75
4d
5
MeOH
THF
6
7d
8
EtOHe–H2O (5 : 1)
EtOHe–H2O (5 : 1)
EtOHe
9d
10
9
EtOHe
10
11
12
13
14
15
16
a Reaction conditions: 3 mmol of styrene, 1 mol% Fe(BF4)2·6H2O,
1 mol% dipic, 1.5 equiv. NaBH4 and 1.5 equiv. t-BuONO, solvent, 6 h
at room temperature under 10 bar of H2. b Determined by GC after the
reaction. c Determined by GC after workup. Isolated yield is given in
parenthesis. d The reaction was performed under normal atmospheric
conditions without additional H2 pressure. e Absolute grade EtOH
used.
Fe(acac)3
Ru(trpy)Cl3
RuCl3·3H2O/dipic
CoCl2·6H2O/dipic
15
a Reaction conditions: 3 mmol of styrene, 1 mol% catalyst, 1 mol%
ligand, 1.5 equiv. NaBH4 and 1.5 equiv. t-BuONO in 5 mL MeOH and
1 mL H2O, 6 h at room temperature under 10 bar of H2. b dipic = 2,6-
pyridine dicarboxylic acid, trpy = 2,2′:6′,2″-terpyridine, dppf = 1,1′-bis-
(diphenylphosphino)ferrocene, pic
=
pyridine-2-carboxylic acid.
c Determined by GC using n-dodecane as an internal standard. Isolated
of styrene, such as 2,3-diphenylbutane, ethyl benzene and
1-phenylethyl amine were however detected by GC in
trace quantities.11,12 Although under normal atmospheric
conditions >90% conversion of styrene was observed in
yield is given in parenthesis.
MeOH–H2O (5 : 1) and that resulted in 82% desired product and selective oxime formation occurs, albeit in low yield (2q).
(Table 1, entry 2 and Table S1†), the best yield of 2 is obtained Although the present method is not applicable for 1,2-diaryl
under dihydrogen pressure (Table 1, entry 3 and Table S1†). substituted olefins, β-methyl substituted styrene derivatives
All the reactions are therefore reported under an additional give good yields of the desired oxime products (2t and 2u).
10 bar H2 pressure. The precise role of the extra H2 is not clear Other reducible groups such as –NO2 (2o) and –CN (2p) are
at present, however, it may be reasonable to assume that the also tolerated. These examples further highlight the beneficial
additional H2 pressure extends a better reducing environment features of the present method since such groups can easily be
towards the formation of the desired products in good to excel- converted to the corresponding amines. Even 4-vinylaniline
lent yields.
gives the desired 1-(4-aminophenyl)ethanone oxime in pre-
Various iron, ruthenium and cobalt salts have also been paratively useful yield (2r). The present reaction protocol thus
tested in the presence of different commercially available bi- proceeds in a highly chemo- and regioselective manner, exclu-
and tridentate ligands (Table 2). It is found that though sively producing acetophenone oxime derivatives.
Fe(BF4)2·6H2O/dipic and Fe(Pc) catalytic species under the
A tentative mechanism for the catalytic cycle has been out-
present reaction protocol (Table 2, entries 11–12) show com- lined in Scheme 2, primarily based on our experimental obser-
parable activity, lower yield is obtained in the latter case. vations. Under the present reaction conditions, exclusive
Hence, optimisation of the suitable reaction conditions reveals formation of acetophenone oxime derivatives indeed rules out
that the in situ generated catalyst derived from 1 mol% the possibility of the involvement of NO+ in the initial stage of
Fe(BF4)2·6H2O and 1 mol% dipic extends maximum activity the reaction, which would otherwise lead to the formation of
and results in acetophenone oxime formation in 90% yield.
2-phenylacetaldehyde oxime and its derivatives on addition to
The optimised reaction conditions indeed allow the substituted ethylenes.13 Hydrogen evolution has also been
reduction of a wide variety of styrene derivatives to generate observed in the initial stage of the reaction on addition of
the corresponding oximes (Table 3). Excellent yields of oximes NaBH4 in the presence of MeOH–H2O (5 : 1). The determining
are obtained with different ortho-, meta- and para-alkyl/alkox- step in the mechanism is the addition of olefin to the metal
ide substituted styrene derivatives (2a–2d, 2l–2m). Halogens at centre of the iron–dipic complex (A) that leads to the formation
different positions of the styrene ring afforded the corres- of σ-alkyliron(III) complex (B). The formation of iron-dipic
ponding oximes in high yields without any dehalogenation complex (A) as the active catalytic species during the reaction
(2e–2k). Remarkably, styrene with a formyl group is found to has also been evidenced by the ESI(+)-MS (Fig. S37†). The reac-
be completely unaffected under the present reaction protocol, tion of B with t-BuONO subsequently, results in the generation
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 38–41 | 39

View Article Online
Communication
Dalton Transactions
Table 3 Substrate scope for iron catalysed nitrosation of olefinsa
of an alkyl nitrite species (C), which is finally converted to D,
the desired oxime.
A set of preliminary mechanistic investigations reveal the
formation of black particles (may be due to Fe(0) or FexBy for-
mation), in the absence of alkene under identical reaction con-
ditions. However, no such black particle formation was
observed in the presence of styrene under the same reaction
conditions. This observation may provide an indirect justifica-
tion in favour of the proposed formation of the iron-alkyl
species as the intermediate which eventually suppresses the
formation of black Fe particles in the presence of the dianionic
dipicolinic acid as the ligand. This also suggests that the possi-
bility of Fe-nanoparticles acting as the active catalytic species
for the hydrogenation process14 in the present case is unlikely.
The homogeneous catalytic route has, however, been estab-
lished by the Hg(0) poisoning experiment as well as by the
TEM and XPS data (see ESI† for details).15 The addition of
Hg(0) in the catalytic process failed to show any poisoning effect
and TEM/XPS did not identify any iron nano-particles/clusters
and iron(0) state, respectively.
It may also be logical to presume that the conversion of C
to D is being facilitated by water since the present catalytic
reaction with styrene using MeOH–D2O (5 : 1) as the solvent
system exhibits a HRMS (ESI+) peak at m/z = 137.0813
(Fig. S40†) corresponding to PhC(Me)NOD (d1-D) (where calcd
m/z (M + H+) = 137.0820). Additionally, water might also play a
role in the hydrolysis of NaBH4 to liberate hydrogen16 in the
presence of the Fe(II) catalyst system and thereby facilitates the
catalytic hydrogenation process under the present reaction
conditions.
In conclusion, an efficient and selective iron-catalysed
reduction protocol has been developed for the conversion of
styrene derivatives to their respective oximes. Good to excellent
yields are obtained for most of the chosen substrates under
mild and benign reaction conditions.
This activity was supported by DST (GKL) and BRNS (DM/
2011/20/37C/13). Financial support received from UGC (fellow-
ship to R.R.) and CSIR (fellowship to A.D.C.), New Delhi, India
is gratefully acknowledged.
a Reaction conditions: 3 mmol of styrene, 1 mol% Fe(BF4)2·6H2O,
1 mol% dipic, 1.5 equiv. NaBH4 and 1.5 equiv. t-BuONO in 5 mL
MeOH and 1 mL H2O, 6 h at room temperature under 10 bar of H2.
b Yields determined by GC after the reaction, isolated yields are in
parentheses. c Yields based on 1H NMR with PhTMS as an internal
standard. d Substrate: trans-β-methyl-styrene. e Substrate: cis-β-methyl-
styrene. f Yield for the reaction done on a 1 g scale.
Notes and references
1 (a) S. Guo, Z. Y. Du, S. G. Zhang, D. M. Li, Z. P. Li and
Y. Q. Deng, Green Chem., 2006, 8, 296; (b) J. J. Peng and
Y. Q. Deng, Tetrahedron Lett., 2001, 42, 403; (c) W. C. Li,
A. H. Lu, R. Palkovits, W. Schmidt, B. Spliethoff and
F. Schuth, J. Am. Chem. Soc., 2005, 127, 12595; (d) M. Boero,
T. Ikeshoji, C. C. Liew, K. Terakura and M. Parrinello, J. Am.
Chem. Soc., 2004, 126, 6280.
2 (a) R. C. Walter, J. Am. Chem. Soc., 1952, 74, 5185;
(b) X. Huang, M. Ortiz-Marciales, K. Huang, V. Stepanenko,
F. G. Merced, A. M. Ayala, W. Correa and M. De Jesus, Org.
Lett., 2007, 9, 1793; (c) Y. K. Choi, M. J. Kim, Y. Ahn and
M.-J. Kim, Org. Lett., 2001, 3, 4099.
Scheme 2 An outline of the tentative mechanistic pathway.
40 | Dalton Trans., 2014, 43, 38–41
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Communication
3 (a) S. Tanase, J.-C. Hierso, E. Bouwman, J. Reedijk, J. ter
Borg, J. H. Bieleman and A. Schut, New J. Chem., 2003, 27,
854; (b) N. Bodor, A. El Koussi, M. Kano and T. Nakamura,
J. Med. Chem., 1988, 31, 100; (c) D. Kirsch, W. Hauser and
N. Weger, Fundam. Appl. Toxicol., 1981, 1, 169.
4 (a) T. Katagi, H. Kataoka, K. Takahashi, T. Fujioka,
M. Kunitomo, Y. Yamaguchi, M. Fujiwara and T. Inoi,
Chem. Pharm. Bull., 1992, 40, 2419; (b) T. Katagi,
H. Kataoka, Y. Konishi, Y. Takata, S. Kitano, M. Yamaki,
T. Inoi, K. Yamamoto, S. Yamamoto and Y. Yamagata,
Chem. Pharm. Bull., 1996, 44, 145; (c) H. Kataoka,
S. Horiyama, M. Yamaki, H. Oku, K. Ishiguro, T. Katagi,
M. Takayama, M. Semma and Y. Ito, Biol. Pharm. Bull.,
2002, 25, 1436; (d) A. M. Nilsson, M. A. Bergstrom,
9 Some recent iron-catalysed reactions of olefins: (a) R. Ray,
A. D. Chowdhury and G. K. Lahiri, ChemCatChem, 2013, 5,
2158; (b) A. D. Chowdhury, R. Ray and G. K. Lahiri,
Chem. Commun., 2012, 48, 5497; (c) A. D. Chowdhury and
G. K. Lahiri, Chem. Commun., 2012, 48, 3448; (d) I. Iovel,
K. Mertins, J. Kischel, A. Zapf and M. Beller, Angew. Chem.,
Int. Ed., 2005, 44, 3913; (e) G. Anilkumar, B. Bitterlich,
F. G. Gelalcha, M. K. Tse and M. Beller, Chem. Commun.,
2007, 289; (f) F. G. Gelalcha, B. Bitterlich, G. Anilkumar,
M. K. Tse and M. Beller, Angew. Chem., Int. Ed., 2007, 46,
7293; (g) B. Morandi, A. Dolva and E. M. Carreira, Org.
Lett., 2012, 14, 2162; (h) J. Y. Wu, B. Moreau and T. Ritter,
J. Am. Chem. Soc., 2009, 131, 12915; (i) J. Y. Wu, B. N. Stanzl
and T. Ritter, J. Am. Chem. Soc., 2010, 132, 13214.
K. Luthman, J. L. G. Nilsson and A. T. Karlberg, Food Chem. 10 A. R. Middleton and G. Wilkinson, J. Chem. Soc., Dalton
Toxicol., 2005, 43, 1627. Trans., 1980, 1888.
5 (a) J. P. Ley and H. J. Bertram, Eur. J. Lipid Sci. Technol., 11 (a) H. Eckert and Y. Kiesel, Angew. Chem., Int. Ed. Engl.,
2002, 104, 319; (b) D. Metodiewa, A. Kochman and
S. Karolczak, IUBMB Life, 1997, 41, 1067; (c) G. O. Puntel,
P. Gubert, G. L. Peres, L. Bresolin, J. B. Rocha,
1981, 20, 473; (b) K. Kano, M. Takeuchi, S. Hashimoto and
Z. Yoshida, J. Chem. Soc., Chem. Commun., 1991, 1728;
(c) M. Takeuchi and K. Kano, Organometallics, 1993, 12, 2059.
M. E. Pereira, V. S. Carratu and F. A. Soares, Arch. Toxicol., 12 Some recent examples of iron-catalysed hydrogenation reac-
2008, 82, 755; (d) R. de Lima Portella, R. P. Barcelos,
A. F. de Bem, V. S. Carratu, L. Bresolin, J. B. da Rocha and
F. A. Soares, Life Sci., 2008, 83, 878; (e) T. Ozen and M. Tas,
J. Enzyme Inhib. Med. Chem., 2009, 24, 1141.
6 (a) E. Abele and E. Lukevics, Org. Prep. Proced. Int., 2000,
32, 235; (b) H. Eshghi and A. Hassankhani, Org. Prep.
Proced. Int., 2005, 37, 575; (c) J. F. Knifton, J. Org. Chem.,
1973, 38, 3296; (d) M. Maheswara, V. Siddaiah,
K. Gopalaiah, V. M. Rao and C. V. Rao, J. Chem. Res., 2006,
tions: (a) T. S. Carter, L. Guiet, D. J. Frank, J. West and
S. P. Thomas, Adv. Synth. Catal., 2013, 355, 880;
(b) M. D. Greenhalgh and S. P. Thomas, Synlett, 2013, 531;
(c) M. D. Greenhalgh and S. P. Thomas, J. Am. Chem. Soc.,
2012, 134, 11900; (d) B. A. F. Le Bailly, M. D. Greenhalgh
and S. P. Thomas, Chem. Commun., 2012, 48, 1580;
(e) B. A. F. Le Bailly and S. P. Thomas, RSC Adv., 2011, 1,
1435; (f) W. M. Czaplik, M. Mayer and A. Jacobi von
Wangelin, ChemCatChem, 2011, 3, 135.
362; (e) J. N. Armor, J. Am. Chem. Soc., 1980, 102, 1453; 13 J. Meinwald, Y. G. Meinwald and T. N. Barker, J. Am. Chem.
(f) L. Zhang, H. Chen, Z. G. Zha and Z. Y. Wang, Chem.
Commun., 2012, 48, 6574.
7 (a) K. Kato and T. Mukaiyama, Bull. Chem. Soc. Jpn., 1991,
Soc., 1964, 86, 4074.
14 P.-H. Phua, L. Lefort, J. A. F. Boogers, M. Tristany and
J. G. de Vries, Chem. Commun., 2009, 3747.
64, 2948; (b) K. Kato and T. Mukaiyama, Chem. Lett., 1990, 15 J. A. Widegren, M. A. Bennett and R. G. Finke, J. Am. Chem.
1395; (c) K. Kato and T. Mukaiyama, Chem. Lett., 1990, Soc., 2003, 125, 10301.
1917; (d) T. Okamoto, K. Kobayashi, S. Oka and S. Tanimoto, 16 (a) H. I. Schlesinger, H. C. Brown, A. E. Finholt,
J. Org. Chem., 1987, 52, 5089; (e) T. Okamoto, K. Kobayashi,
S. Oka and S. Tanimoto, J. Org. Chem., 1988, 53,
4897; (f) K. Sugamoto, Y. Hamasuna, Y. Matsushita and
T. Matsui, Synlett, 1998, 1270.
8 S. Prateeptongkum, I. Jovel, R. Jackstell, N. Vogl,
C. Weckbecker and M. Beller, Chem. Commun., 2009, 1990.
J. R. Gilbreath, H. R. Hoekstra and E. K. Hyde, J. Am. Chem.
Soc., 1953, 75, 215; (b) G. N. Glavee, K. J. Klabunde,
C. M. Sorensen and G. C. Hadjipanayis, Inorg. Chem., 1995,
34, 28; (c) G. D. Forster, L. F. Barquin, R. L. Bilsborrow,
Q. A. Pankhurst, I. P. Parkin and W. A. Steer, J. Mater.
Chem., 1999, 9, 2537.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 38–41 | 41