A new avenue to the Dakin reaction in H2O2-WERSA

Article abstract of DOI:10.1039/c5ra20133k

We have developed a novel protocol to realize the Dakin reaction in a more greener way. In fact, by the use of H₂O₂-WERSA, we can oxidize aromatic arylaldehydes to phenols at room temperature. It is remarkable that the catalytic system does not require activation or any toxic ligand, additive/promoter, transition metal catalyst, base, organic solvent and so on. A range of substituted hydroxylated benzaldehydes were screened to investigate the scope of this protocol.

Full text of DOI:10.1039/c5ra20133k

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DOI: 10.1039/C5RA20133K
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A new avenue to Dakin reaction in H2O2–WERSA
Bishwajit Saikia*a and Parinita Borahb
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
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We have developed a novel protocol to realize Dakin reaction in a more this key transformation (Figure 1).
greener way. In fact, by the using of H2O2–WERSA, we can oxidize aromatic
arylaldehydes to phenols at room temperature. It is remarkable that the
Cl
N
N
O
O
catalytic system does not require activation or any toxic ligand,
additive/promoter, transition metal catalyst, base, organic solvent and so
on. A range of substituted hydroxylated benzaldehydes were screened to
investigate the scope of this protocol.
Cat.
N
Cl
N
O
O
H2O2
NaHCO3
Ref. 4a
95% MeOH aq
rt, upto 6 h
Conversion of o-and p-hydroxybenzaldehydes to dihydric phenols
using alkaline hydrogen peroxide is generally known as Dakin
oxidation.1 Dihydric phenols and their derivatives are practically
important substrates and are used extensively in various fields
particularly in agrochemicals, antioxidants, pharmaceuticals,
flavoring agents, polymerization inhibitors, photographic processes
etc.2 Dakin’s original procedure utilized excess hydrogen peroxide
and sodium hydroxide at elevated temperatures.1a Till date many
methods have been investigated to perform this transformation.3
The propagation of methods available to undertake this particular
transformation indicates to the synthetic usefulness; and, yet,
major problems remain to anyone wishing to apply these methods
within an effortless synthetic context, mostly arising from the
harshness. Most of these reactions were performed in traditional
organic solvents and resulted in considerable environmental
pollution, often requiring activation by metal catalysts and use of
H2O2 activator. Moreover, health, safety and environmental issues
associated with the use of many conventional organic solvents have
led to their use being strictly curtailed. Due to environmental,
economical, and safety concerns, it is highly desirable to develop
green, cheap and easy procedure with high durability and activity
for Dakin reaction. Similarly, the design of efficient catalysts system
producing high yields under aerobic conditions continues to be an
important challenge. In this report we offered a solution to this
problem in the form a novel and highly mild green alternative for
Cl
N
N
N
O
Cat.
N
Cl
O
O
O
O2
NaHCO3
Ref. 4b
MeCN/H2O
rt, upto 7.5 h
NH2CONH2
HOOH
(Urea-Hydrogen
peroxide adduct)
55-85oC, upto 1.5 h
Ref. 4c
CHO
OH
H2O2/CH3ReO3
[bmim]BF4 or [bmim]PF6
50oC, upto 6 h
Ref. 4d
R
R
2Na2CO3.3H2O2
(Sodium percarbonate)
THF-H2O (10mL + 4 mL)
Sonicated in an
Ultrasound bath
upto 8 h
Ref. 4f
H2O2-H3BO3
H2SO4, THF
rt to 60oC, upto 24 h
Ref. 4h
mCPBA
rt, upto 10 min
Ref. 4i
H2O2
a.Department of Chemistry, Dibrugarh University, Dibrugarh–786004, Assam, India.
E-mail: bishwajitsaikia@gmail.com; Tel: +91 9954314676 (M).
WERSA, rt
Our Method
b.Department of Chemistry, Bahona College, Jorhat–785101, Assam, India.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
Fig. 1 Previous works vs our work
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J. Name., 2013, 00, 1-3 | 1
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Experiments should involve the use of alternative solvents which be successfully achieved when H2O2–WERSA is used as catalyst
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DOI: 10.1039/C5RA20133K
are not only eco-friendly but also be easily available anywhere in system even in the case of species that are deactivated. In
bulk quantities at very cheap price. Rice straw is a highly abundant comparison to existing reagents, this aerobic oxidation of
natural waste material across the world and therefore, its hydroxylated benzaldehydes with this novel H2O2–WERSA system
application in organic synthesis as reaction medium will draw appears to be a superior alternative in terms of shorter reaction
significant awareness from the point of environmental issues. time, cleaner product formation, commercially feasibility as well as
Because green chemistry efficiently utilises (preferably renewable) environmental sustainability.
raw materials, eliminates waste and avoids the use of
toxic/hazardous solvents and reagents in the manufacture and Table 1. Optimization of reaction conditionsa
application of chemical products.4 In our effort toward developing
CHO
OH
green and sustainable catalytic methods, we now wish to report an
extended study of the catalytic behaviour of “Water Extract of Rice
Straw Ash” (WERSA)5 as catalysts as well as reaction medium in the
Dakin oxidation involving hydroxylated benzaldehydes. We are
utilizing WERSA as a cheap, non-toxic, and green catalytic media in
this important synthetic conversion. WERSA has been prepared by
burning rice straw to ashes and that ash was suspended in distilled
water in a glass beaker and mechanically stirred for a few minutes
at room temperature. Finally, the mixture was filtered and the
filtrate was abbreviated as WERSA here (Figure 2). Likewise,
hydrogen peroxide is one of the cheapest environmentally friendly
and easy to handle oxidizing agents widely used for a range of
oxidative transformations over the years.6
OH
OH
30% H2O2
WERSA, rt
Entry H2O2 (equiv.)
Time (h)
Yieldb (%)
1
2
3
1
1.5
2
4
3
2
75
88
98
a
Reaction conditions: salicylaldehyde (1 mmol), H2O2 in WERSA (3
mL) at room temperature.
b Isolated yields.
Dakin oxidation is a variation of the Baeyer–Villiger oxidation (BVO)
that converts benzaldehyde (1) to phenol (4) by BVO (migration of
aryl group) followed by hydrolysis of the aryl formate intermediate
(3), effectively oxidizing both aryl and acyl sp2 carbons. Literature
report reveals that rice straw ash consists of oxides of SiO2
(74.31%), Al2O3 (1.40%), Fe2O3 (0.73%), TiO2 (0.02%), CaO (1.61%),
MgO (1.89%), K2O (11.30%), Na2O (1.85%), P2O5 (2.65%) etc.8 Oxides
of potassium, sodium, magnesium and calcium react with water to
produce hydroxides of these metals and therefore, we strongly
believe that these alkali metal hydroxides (particularly KOH and
NaOH) work as internal bases here to assist the Dakin reactions
smoothly at room temperature in absence of any H2O2 activators or
organic co-solvents. The possible H2O2–WERSA catalysed Dakin
oxidation mechanism is illustrated in Scheme 1.
Fig. 2 Preparation of WERSA
Fig. 2 Preparation of WERSA
The catalytic activity of H2O2–WERSA system in the Dakin oxidation
was tested by using salicylaldehyde in the presence of 1 equiv. of
H2O2 in WERSA at room temperature. The reaction after 4 h gave
the product catechol in 75% yield (Table 1, entry 1). On using 1.5 to
2.0 equiv. of H2O2, the yield of the desired product was increased
(88 and 98% respectively) (Table 1, entries 2 & 3). We have
calculated the conversion of salicylaldehyde to catechol by NMR
spectroscopy, utilizing CDCl3 as an internal standard. Subsequently
the Dakin oxidation of variety of hydroxylated benzaldehydes,
including activated and deactivated ones (Table 2; entries 1–16),
was examined using H2O2–WERSA as the catalyst system and yields
were excellent. Results were very consistent with reactions
achieved with high yields and purities regardless of the
substituent’s such as –OH, –OCH3, –CH3, –C2H5, –NO2, –Br, –Cl etc.
on the aromatic ring and again with all reactions run in air (Table 2;
entries 1–16). Therefore, this is the simplest example for Dakin
oxidation among all other oxidation systems so far reported. The
method in general provides good to excellent yields of oxidized
products. Interestingly, the formation of undesired benzyl alcohols
or benzoic acids was not detected in this reaction condition.7 Our
findings reflect that the goal of carrying out the Dakin reactions can
O
OH
H2O2
H
WERSA, rt
OH
OH
1
4
Mechanism:
Base source is WERSA
Step 1:
HOOH + B
O
HOO
+ BH
Base = B
H
O
OH
O
OOH
H
Step 2:
OH
OH
1
2
H
O
OH
O
O
O
Ar-migration
Step 3:
Step 4:
H
OH
OH
2
3
(aryl formate intermediate)
O
O
OH
Hydrolysis
H
OH
OH
4
3
2 | J. Name., 2012, 00, 1-3
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Scheme 1. Possible H2O2–WERSA catalysed Dakin oxidation
mechanism.
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DOI: 10.1039/C5RA20133K
CHO
OH
OH
OH
OH
13
14
15
16
3
90
Table 2. Conversion of arylaldehydes to phenols in H2O2–WERSA
system at room temperaturea
O2N
O2N
CHO
CHO
OH
OH
OH
30% H2O2 (2 equiv.)
WERSA, rt
3
3
90
88
R
R
OC2H5
OH
OC2H5
CHO
Entry
1
Starting
Material
Product
Time
(h)
Yieldb
(%)
OH
CHO
OH
OH
OH
2
2
2
98
98
96
OH
CHO
OH
OH
3
85
CHO
2
3
MeO
OMe
MeO
OMe
HO
HO
OH
OH
a
Reaction conditions: arylaldehydes (1 mmol), H2O2 (2 equiv
relative to the amount of substrates) in WERSA (3 mL) at room
CHO
OH
OH
OH
temperature.
b Isolated yields.
CHO
OH
OH
OH
OH
OH
Conclusions
4
5
2
95
92
In conclusion, we have described a novel Dakin oxidation
protocol with 30% H2O2 in “Water Extract of Rice Straw Ash”
(WERSA) at room temperature. This system works with a wide
scope of substrates, without using any other ligands, bases,
additives, organic co-solvents and higher yields compared to
those reported earlier with various Dakin oxidation systems.
Since Dakin oxidation is a widely used reaction in industry, this
cheap and simple system definitely will attract attentions and
find potential application in near future. Our strategy would be
a potential tool for the direct utilization of WERSA for attaining
different industrially important catalytic reactions.
CHO
CHO
OH
OH
2.5
OMe
OH
OMe
OH
6
2.5
92
OMe
OH
OMe
CHO
Acknowledgment
7
8
3
2
2
2
2
90
96
94
94
92
P. Borah is highly thankful to UGC, New Delhi for the financial
support of this study.
OMe
OH
OMe
OH
OH
OH
OH
CHO
References
1
(a) H. D. Dakin, Am. Chem. J., 1909, 62, 477–498; (b) H. D.
Dakin, H. T. Clarke and E. R. Taylor, Catechol. Org. Synth.
Br
Br
OH
CHO
CHO
CHO
Coll., 1941,
1, 149–152; (c) H. D. Dakin, Org. Synth., 1933,
OH
Br
OH
149–154; (d) H. C. Hassall, Organic Reactions Wiley, New
9
York 1967, Vol. 9, 73; (e) M. Matsumoto, H. Kobayashi and Y.
Br
Hotta, J. Org. Chem., 1984, 49, 4740–4741.
OH
OH
2
(a) R. Anand, R. Maheswari, K. U. Gore and V. R. Chumbhale,
OH
OH
Chem. Commun., 2002, 3, 321–326; (b) K. Nakajima and A.
10
11
Yamashita, JP Patent 53009734, 1978; (c) H. R. Bjorsvik, L.
Liguori and F. Minisci, Org. Process Res. Dev., 2000, , 534–
4
Cl
Cl
543; (d) G. S. Clark, Perfum. Flav., 1990, 15, 45–54; (e) Y. M.
C. Sunny and W. M. Yu, US Patent 2002192606, 2002; (f) E.
Okutsu and H. Tsuzuki, JP Patent 2002116527, 2002; (g) E.
Klarmann, L. W. Gatyas and V. A. Shternov, J. Am. Chem.
Soc., 1932, 54, 298–305; (h) E. Klarmann, L. W. Gatyas and V.
A. Shternov, J. Am. Chem. Soc., 1931, 53, 3397–3407; (i) E.
Klarmann, L. W. Gatyas and V. A. Shternov, J. Am. Chem.
Soc., 1932, 54, 1204–1211.
OH
Cl
OH
Cl
CHO
OH
OH
Br
OH
Br
12
3
88
Br
Br
This journal is © The Royal Society of Chemistry 20xx
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3
(a) S. Chen, M. S. Hossain and F. W. Foss Jr., Org. Lett., 2012,
14, 2806–2809; (b) S. Chen and F. W. Foss Jr., Org. Lett.,
2012, 14, 5150–5153; (c) R. S. Varma and K. P. Naicker, Org.
1977–1986; (e) K. Bahrami, M. M. Khodaei and F. Naali, J.
View Article Online
Org. Chem., 2008, 73, 6835–6837; (f) K. Bahrami, M. M.
Khodaei and M. Sheikh Arabi, J. Org. CDheOmI: 1.,02.1003190/,C755R,A260210383K–
6213; (g) K. Bahrami, M. M. Khodaei and M. Soheilizad, J.
Org. Chem., 2009, 74, 9287–9291; (h) K. Bahrami, M. M.
Lett., 1999,
1, 189–191; (d) R. Bernini, A. Coratti, G.
Provenzano, G. Fabrizi and D. Tofani, Tetrahedron, 2005, 61
,
1821–1825; (e) T. V. Hansen and L. Skattebøl, Tetrahedron
Lett., 2005, 46, 3357–3358; (f) G. W. Kabalka, N. K. Reddy
and C. Narayana, Tetrahedron Lett., 1992, 33, 865–866; (g) S.
Yamazaki, Chem. Lett., 1995, 127–128; (h) A. Roy, K. R.
Reddy, P. K. Mohanta, H. Ila and H. Junjappa, Synth.
Commun., 1999, 29, 3781–3791; (i) E. T. da Silva, C. A.
Camara, O. A. C. Antunes, E. J. Barreiro and C. A. M. Fraga,
Synth. Commun., 2008, 38, 784–788; (j) J. L. Zambrano and R.
Dorta, Synlett, 2003, 1545–1546; (k) G. J. Brink, ten, I. W. C.
E. Arends and R. A. Sheldon, Chem. Rev., 2004, 104, 4105–
4124.
Khodaei and P. Fattahpour, Catal. Sci. Technol., 2011, 1, 389–
393.
7
8
(a) K. Kaneda, S. Haruna, T. Imanaka, M. Hamamoto, Y.
Nishiyama and Y. Ishii, Tetrahedron Lett., 1992, 33, 6827–
6830; (b) C. Bolm, G. Schlingloff and K. Weickhardt,
Tetrahedron Lett., 1993, 34, 3405–3408; (c) K. Kaneda, S.
Ueno, T. Imanaka, E. Shimotsuma, Y. Nishiyama and Y. Ishii,
J. Org. Chem., 1994, 59, 2915–2917.
B. M. Jenkins, R. R. Bakker and J. B. Wei, Biomass Bioenergy,
1996, 4, 177–200.
4
5
6
R. A. Sheldon, I. W. C. E. Arends and U. Hanefeld, Green
Chemistry and Catalysis, Wiley-VCH, Weinheim, 2007.
P. R. Boruah, A. A. Ali, M. Chetia, B. Saikia and D. Sarma,
Chem. Commun., 2015, 51, 11489–11492.
(a) Catalytic Oxidations with Hydrogen Peroxide as Oxidant;
G. Strukul, Ed.; Kluwer Academic: Dordrecht, 1992; (b) C. W.
Jones, Applications of Hydrogen Peroxide and Derivatives;
Royal Society of Chemistry: Cambridge, 1999; (c) W. R.
Sanderson, Pure Appl. Chem., 2000, 72, 1289–1304; (d) R.
Notori, A. Masao and S. Kazuhiko, Chem. Commun., 2003,
4 | J. Name., 2012, 00, 1-3
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Graphical Abstract:
A new avenue to Dakin reaction in H2O2–WERSA
Bishwajit Saikia*a and Parinita Borahb
a Department of Chemistry, Dibrugarh University, Dibrugarh–786004, Assam, India.
E-mail: bishwajitsaikia@gmail.com; Tel: +91 9954314676 (M).
b Department of Chemistry, Bahona College, Jorhat–785101, Assam, India..
We have developed a novel protocol to realize the Dakin reaction in H2O2–WERSA at
room temperature. It is highly remarkable that the catalytic system does not require activation
or any toxic ligand, additive/promoter, transition metal catalyst, base, organic solvent and so
on.
CHO
R
H2O2, WERSA, rt
OH
R