Solvent-free chemoselective oxidation of thioethers and thiophenes by mechanical milling

Article abstract of DOI:10.1039/c2cc36365h

Organosulphur compounds can be easily and selectively oxidized to sulfones using a small excess of Oxone (1.6 eq.) under solventless mechanical milling conditions. This green procedure has been efficiently applied to a series of model compounds and to the desulphurization of medium/high sulphur content paraffins (up to 3000 mg kg^-1).

Full text of DOI:10.1039/c2cc36365h

View Online / Journal Homepage
ChemComm
Accepted Manuscript
This is an Accepted Manuscript, which has been through the RSC Publishing peer
review process and has been accepted for publication.
Accepted Manuscripts are published online shortly after acceptance, which is prior
to technical editing, formatting and proof reading. This free service from RSC
Publishing allows authors to make their results available to the community, in
citable form, before publication of the edited article. This Accepted Manuscript will
be replaced by the edited and formatted Advance Article as soon as this is available.
Chemical Communications
www.rsc.org/chemcomm
Volume 46
| Number 32 | 28 August 2010 | Pages 5813–5976
To cite this manuscript please use its permanent Digital Object Identifier (DOI®),
which is identical for all formats of publication.
More information about Accepted Manuscripts can be found in the
Information for Authors.
Please note that technical editing may introduce minor changes to the text and/or
graphics contained in the manuscript submitted by the author(s) which may alter
content, and that the standard Terms & Conditions and the ethical guidelines
that apply to the journal are still applicable. In no event shall the RSC be held
responsible for any errors or omissions in these Accepted Manuscript manuscripts or
any consequences arising from the use of any information contained in them.
ISSN 1359-7345
COMMUNICATION
FEATURE ARTICLE
J. Fraser Stoddart et al.
Directed self-assembly of a
ring-in-ring complex
Wenbin Lin et al.
Hybrid nanomaterials for biomedical
applications
1359-7345(2010)46:32;1-H
www.rsc.org/chemcomm
Registered Charity Number 207890

Page 1 of 3
ChemComm
Dynamic Article Links ►
ChemComm
View Online
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
COMMUNICATION
Solvent-free chemoselective oxidation of thioethers and thiophenes by
mechanical milling
a
a
a
a
Giancarlo Cravotto, * Davide Garella, Diego Carnaroglio, Emanuela Calcio Gaudino and Ornelio
Rosati.
b
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
5
Organosulphur compounds can be easily and selectively 50 While liquid fuels can easily be subjected to power ultrasound or
®
6
oxidized to sulfones using a small excess of Oxone (1.6 eq)
hydrodynamic cavitation, paraffin can only be treated with
7
under solventless mechanical milling. This green procedure
has been efficiently applied to a series of model compounds
and to the desulphurization of medium/high sulphur content
paraffins (up to 3000 mg/kg).
specific high-shear mixers. We believe that mechanical milling
can also be used to treat paraffins that rapidly melt under intense
friction. To the best of our knowledge, this is the first study to
carry out paraffin ODS and, thanks to the starting material's solid
nature (m.p. 50-80°C), the first process to be carried out in
solventless and mechanochemical conditions.
Chemical reactions in ball mills have also attracted large amounts
of attention from organic chemists over the last decade. This
method allows reactions to be carried out in the solid state and
1
0
5
5
Petroleum and paraffin contain a large variety of sulphur
compounds (thiols, sulfides, disulfides, thiophenes, benzo and
dibenzothiophenes) which generate SO and airborne particulate
emissions during combustion. Catalytic hydrodesulphurization
HDS) has been the accepted method for the removal of
8
,9
1
2
2
3
3
5
0
5
0
5
2
60
1
0-13
can also reduce solvent use (when required),
an attractive option for other application fields as well.
which makes it
(
1
4
organosulphur compounds for some time. In this process H is
2
converted to H S and subsequently reacted with O in the Claus
After a preliminary screening of several solid oxidants (sodium
2
2
process to provide H O and elemental sulphur. Various factors
persulphate, potassium superoxide, sodium tungstate) we selected
2
®
affect HDS catalyst performance and these include the type of 65 Oxone (2 KHSO
, KHSO
, K
SO
) for use in our studies. It is a
5
4
2
4
commercially available, white, granular, solid peroxygen that
enables green, efficient non-chlorine oxidation and whose
reaction by-products are generally recognized as safe. Owing to
feed material and the chemical nature of the organosulphur
compounds (i.e. aliphatic sulphur is more easily removed than
1
aromatic sulphur). HDS reactivity follows this order: thiophenes
®
>
benzothiophenes
>
dibenzothiophenes
>
its high stability and efficiency, Oxone has found many
2
15
16
17
dimethyldibenzothiophenes. Oxidative desulphurization (ODS) 70 applications
in the oxidation of amines,
alcohols,
1
8
19
20
is an interesting alternative, or possibly complementary, process
which works by means of a wide range of suitable oxidizing
agents, such as peroxy organic acids, hydroperoxides, nitrogen
aldehydes and ketones, the epoxidation reactions of alkenes,
C–H bond oxidation processes
reaction. In particular, Oxone can also be applied to
sulfoxidation reactions in aqueous acetone or methanol, and to
2
1
and the Baeyer-Villiger
2
2
®
2
3
3
oxides, peroxy salts, ozone, etc. ODS is attracting significant
research interest, mainly as a means of treating light oils, because 75 the mechanochemical oxidation of para-substituted anilines to
4
24
®
of its ease of use and high efficiency. When using the ODS
nitrosobenzenes. Yu et al. have reported the use of Oxone in
technique it was found that sulphur compound reactivity was
somehow the opposite to what would have been expected from
the use of HDS. Generally speaking, the process consists of two
steps: 1) oxidation whereby compounds are converted into
sulfoxides and sulfones, and 2) their subsequent removal by
extraction or adsorption. All of these oxidations occur in the
heterogeneous phase as either liquid/solid or liquid/liquid
reactions and therefore the optimization of mass and heat transfer
is a crucial feature.
the selective oxidation of organic sulfides under stirring (12h) at
2
5
6
0°C. The sulfoxide/sulfone ratio was strongly dependent on
the solvent (ethanol vs. water).
8
0
In this communication we report the solventless selective
oxidation of several organosulphur compounds to sulfones, under
®
mechanical milling using Oxone , and an application of this
optimized procedure in the desulphurization of medium to high
sulphur content paraffins.
4
4
0
5
85
2
6
Scheme 1. Chemoselective oxidation of sulphides to sulfones.
a
Dipartimento di Scienza e Tecnologia del Farmaco, University of Turin,
Via P. Giuria 9, I-10125 Turin, Italy.
E-mail: giancarlo.cravotto@unito.it; fax +39 011 6707687
b
Dipartimento di Chimica e Tecnologia del Farmaco. Via del liceo 1, I-
0
6123 Perugia, Italy.
This article is part of the ChemComm 'Mechanochemistry: fundamentals
and applications in synthesis' web themed issue.
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

ChemComm
Page 2 of 3
View Online
A number of exploratory experiments used 3,6-dithiaoctane-1,8- 25 was washed with CHCl to recover the organic compounds and to
3
®
diol (Lindlar catalyst poison) and 4-(methylthio)benzaldehyde as
model compounds as well as a series of S-heterocycles
clean the Oxone . This procedure was repeated over three cycles
highlighting the fact that Oxone can be easily reused when it is
®
(
thiophene, benzothiophene, dibenzothiophene and substituted
in stoichiometric excess (Table 2).
5
0
5
derivatives). All substrates exclusively afforded the sulfone as the
oxidation product and no traces of sulfoxides were detected, a 30 paraffin ODS was conceived as the organosulphur derivatives
With these results at hand, a means to apply this procedure to
fact which effectively highlights the chemoselectivity of
tested in the previous reaction were quite similar to those present
®
29
mechanochemical oxidation with Oxone . All substrates, apart
in petroleum paraffin. We tested the protocol on two types of
from nitrothiophene, gave excellent conversions and yields. All
the reactions were carried out in low oxidant excess (1 : 1.6 molar
paraffin, P1 and P2, that differ in their sulphur content (330 and
3000 mg/kg respectively). P1 is white (m.p. 50-55°C) while P2 is
1
2
7
ratio) and samples were analyzed by GC-MS after 30 and 90 35 yellowish (m.p. 75-80°C).
1
13
minutes (Table 1). FTIR and H- C-NMR spectra of the isolated
®
Table 2. Oxone reuse starting from an 1:2 molar excess.
2
8
products confirmed the sulfone structures. For the sake of
comparison with conventional techniques, all the reaction
mixtures were simply heated at 80°C for 90 min (neat or in
toluene solution under stirring). In all cases only the starting
material was detected.
a
Entry
9
Substrate
Cycles
Yield (%)
1
1
2
3
100
100
<1
a
2
6
Isolated yields (flash chromatography PE\EtOAc, 9:1)
Table 1. Sulphur compound oxidation under mechanical milling.
Sulfone
Conversion Yielda
After oxidative treatment in the ball mill, the paraffins were
directly filtered on a thermostatted silica cartridge to remove the
sulfones which were easily separated because of their higher
polarity. The residual sulphur content after the process was 13
Time
Entry
1
Substrate
(min)
4
0
(
%)
(%)
3
0
mg/kg for P1 and 155 mg/kg for P2.
30
9
8
Differently to what appears at a first glance the method is
potentially scalable and suitable big scale ball mills are already
used for industrial application (i.e. cement works factories). The
9
0
100
99
45
®
possibility to reuse Oxone when in stoichiometric excess is
3
9
0
0
13
11
97
2
3
another important feature for the scaling up of the process.
Moreover the use of thermostatted silica cartridges (over the
paraffin melting point) enable the filtration without the use of
50 solvents. In pilot plants the full recovery of paraffins from
columns or cartridges can be enhanced by means of a stream of
hot steam. Although the regulation threshold value of 20 ppm is
reached only for one type of paraffin (from 330 ppm to 13 ppm),
it is of high significance the cutting down of sulphur content from
55 3000 to 150 ppm, because this product would require a very mild
step of catalytic hydrodesulphurization.
100
b
0
0
-
30
b
9
0
-
4
5
6
30
35
100
34
98
9
0
In summary a new chemoselective protocol for the oxidation of
organosulphur compounds to sulfones has been developed. The
3
9
0
0
31
27
97
®
solventless mechanochemical reaction with Oxone is effective
100
60
on the most common organosulphur compounds that are present
in paraffin as pollutants and are stubborn to HDS treatment. This
makes this ODS procedure an excellent cost-effective
compliment to HDS. It is worth noting that the same reaction
carried out under stirring at 80°C failed. The low residual sulphur
content in the two paraffins tested confirms the potential for
application that oxidative desulphurization by mechanical milling
presents.
30
20
100
19
99
9
0
65
3
9
0
0
27
25
99
7
100
a
Isolated yields (flash chromatography PE\EtOAc, 9:1 as eluent)
Starting material
Financial support from MIUR PRIN 2008 “A Green Approach
70 to Process Intensification in Organic Synthesis” is gratefully
b
acknowledged.
2
0
The oxidant and its reuse were also investigated in successive
reactions with DBT, as it is one of the most common sulphur
compounds in petroleum derivatives (initial molar ratio
Notes and references
1
2
T. C. Ho, Catal. Today, 2004, 98, 3–18.
C. Song, Catal. Today, 2003, 86, 211–263.
®
DBT/Oxone 1:2). At the end of the reaction, the solid mixture
2
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 3
ChemComm
View Online
3
4
J. M. Campos-Martin, M. C. Capel-Sanchez, P. Perez-Presas, J. L. G.
GC conditions were: injection split 1:20, injector temperature 250°C,
detector temperature 280°C. Gas carrier: helium (1.2 mL/min),
temperature program: from 70°C (2 min) to 300°C at 5°C/min.
75 28 See Supplementary material
Fierro, J. Chem. Technol. Biotechnol., 2010, 85, 879–890.
M. C. Capel-Sanchez, P. Perez-Presas, J. M. Campos-Martin, J. L. P
Fierro, Catal. Today, 2010, 157, 390–396.
F. A. Duarte, P. Mello, C. A. Bizzi, M. A. G. Nunes, E. M. Moreira,
M. S. Alencar, H. N. Motta, V. L. Dressler, E. M. M. Flores, Fuel
®
5
0
5
0
5
0
5
0
5
0
5
0
5
0
5
29 The paraffin (0.5-1g) and the Oxone were added to the milling
beaker (Molar ratio S vs oxidant 1 : 25) and milled as described in
note 26 for 40 min. The final temperature of the reaction mixture was
about 74-76°C. The sample was kept hot (80-90°C) and was directly
2
011, 90, 2158-2164.
6
7
8
9
J. Ozonek, Application of Hydrodynamic Cavitation in
Environmental Engineering, CRC Press 2012.
H. Abbas, G. Borsinger, G. Gregory, A. G. Rayford, H. Aziz,
WO2010.093507.
B. Rodríguez, A. Bruckmann, T. Rantanen, C. Bolm, Adv. Synth.
Catal., 2007, 349, 2213-2233.
A. Stolle, T. Szuppa, S. E. S. Leonhardt, B. Ondruschka, Chem. Soc.
Rev., 2011, 40, 2317-2329.
80
filtered using a thermostatted silica cartridge (3 g).
1
1
2
2
3
3
4
4
5
5
6
6
7
30 Total sulphur amount was measurement with elemental analyzer:
®
Multi EA 5000.
1
1
0 K. Tanaka, F. Toda, Chem. Rev., 2000, 100, 1025-1074.
1 K. Tanaka, Solvent-free Organic Synthesis (2nd Ed.), Wiley-VCH,
Weinheim, 2008.
1
2 G. Cravotto, D. Garella, S. Tagliapietra, A. Stolle, S. Schüßler, S.E.S.
Leonhardt, B. Ondruschka, New. J. Chem. 2012, 36, 1304-1307.
3 M. O´Brien, R. Denton, S. V. Ley, Synthesis, 2011, 8, 1157-1192.
4 S. L. James, C. J. Adams, C. Bolm, D. Braga, P. Collier, T. Friščić, F.
Grepioni, K. D. M. Harris, G. Hyett, W. Jones, A. Krebs, J. Mack, L.
Maini, A. G. Orpen, I. P. Parkin, W. C. Shearouse, J. W. Steed, D. C.
Waddell, Chem. Soc. Rev. 2012, 41, 413-447.
1
1
1
5 M. Eissen, M. Strudthoff, S. Backhaus, C. Eismann, G. Oetken,
S. Kaling, D. Lenoir, J. Chem. Educ., 2011, 88, 284-291.
6 (a) J. D. Fields, P. J. Kropp, J. Org. Chem., 2000, 65, 5937-5941;
1
(b) K. S. Webb, V. Seneviratne, Tetrahedron Lett., 1995, 36, 2377–
2378.
17 (a) C. Bolm, A. S. Magnus, J. P. Hildebrand, Org. Lett., 2000, 2,
1
173–1175; (b) M. Hirano, M. Oose, T. Morimoto, Bull. Chem. Soc.
Jpn., 1991, 64, 1046–1047.
B. R. Travis, M. Sivakumar, G. O. Hollist, B. Borhan, Org. Lett.,
2003, 5, 1031–1034.
1
1
2
8
9
M. Uyanik, M. Akakura, K. Ishihara, J. Am. Chem. Soc., 2009, 131,
2
51–262.
0 (a) Z.-X. Wang, Y. Tu, M. Frohn, J.-R. Zhang, Y. Shi, J. Am. Chem.
Soc., 1997, 119, 11224–11235; (b) D. Yang, Acc. Chem. Res., 2004,
37, 497-505; (c) S. E. Denmark, D. C. Forbes, D. S. Hays, J. S.
DePue, R. G. Wilde, J. Org. Chem., 1995, 60, 1391–1407; (d) M.
Frohn, Z.-X. Wang, Y. Shi, J. Org. Chem., 1998, 63, 6425–6426;
(
4
e) N. Hashimoto, A. Kanda, Org. Process Res. Dev., 2002, 6, 405-
06.
21 P. Liu, Y. G. Liu, E. L. M. Wong, S. Xiang, C. M. Che, Chem. Sci.,
011, 2, 2187–2195.
2
22
(a) A. Chrobok, Tetrahedron, 2010, 66, 6212–6216; (b) M. E.
Gonzalez-Nunez, R. Mello, A. Olmos, G. Asensio, J. Org. Chem.,
2
005, 70, 10879–10882; (c) M. Renz, B. Meunier, Eur. J. Org.
Chem., 1999, 4, 737-750.
3 (a) B. M. Trost, D. P. Curran, Tetrahedron Lett., 1981, 22, 1287-
290; (b) K. S. Webb, Tetrahedron Lett., 1994, 35, 3457–3460; (c) F.
A. Davis, S. G. Lal, H. D. Durst, J. Org. Chem., 1988, 53, 5004–
007.
24 I. Huskić, I. Halasz, T. Friščić, H. Vančik, Green Chem., 2012, 14,
597–1600.
B. Yu, A.-H. Liu, L.-N. He, B. Li, Z.-F. Diao Y.-N Li, Green Chem.,
012, 14, 957–962.
2
1
5
1
2
2
5
6
2
®
The organosulphur compound (1 mmol) and the Oxone (1.6 mmol)
were poured into the milling beaker. We used a planetary ball mill
PM100 Retsch GmbH, equipped with a single milling beaker
(
5
stainless steel, 125 mL). The solid reaction mixture was milled at
00 min with 25 milling balls (Ø=10 mm, stainless steel). At the
-
1
half time of reactions, the direction of rotation was inverted. Samples
are extracted three time with CHCl
by GC-MS.
3
and the filtered solution analysed
2
7
Gaschromatography-mass spectrometry (GC-MS) analyses were
performed in gaschromatograph Agilent 6890 (Agilent
a
Technologies - USA) fitted with a mass detector Agilent Network
5973, using a 30 m long capillary column, i.d of 0.25 mm and film
thickness 0.25 μm.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3