Nonanebis(peroxoic acid): A stable peracid for oxidative bromination of aminoanthracene-9,10-dione

Article abstract of DOI:10.3762/bjoc.10.90

A new protocol for the oxidative bromination of aminoanthracene-9,10-dione, which is highly deactivated towards the electrophilic substitution is investigated. The peracid, nonanebis(peroxoic acid), possesses advantages such as better stability at room temperature, it is easy to prepare and non-shock sensitiv as compared to the conventional peracids. The present protocol has a broad scope for the bromination of various substituted and unsubstituted aminoanthracene-9,10-diones.

Full text of DOI:10.3762/bjoc.10.90

Nonanebis(peroxoic acid): a stable peracid for
oxidative bromination of aminoanthracene-9,10-dione
Vilas Venunath Patil and Ganapati Subray Shankarling*
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2014, 10, 921–928.
Department of Dyestuff Technology, Institute of Chemical
Technology, N. P. Marg, Matunga, Mumbai - 400019, India.
Tel.: 91-22-33612708, Fax: 91-22-33611020
doi:10.3762/bjoc.10.90
Received: 27 November 2013
Accepted: 01 April 2014
Published: 24 April 2014
Email:
Ganapati Subray Shankarling* - gsshankarling@gmail.com
Associate Editor: B. Stoltz
* Corresponding author
© 2014 Patil and Shankarling; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
aminoanthracene-9,10-dione; benzanthrone; KBr; nonanebis(peroxoic
acid); oxidative bromination
Abstract
A new protocol for the oxidative bromination of aminoanthracene-9,10-dione, which is highly deactivated towards the electrophilic
substitution is investigated. The peracid, nonanebis(peroxoic acid), possesses advantages such as better stability at room tempera-
ture, it is easy to prepare and non-shock sensitiv as compared to the conventional peracids. The present protocol has a broad scope
for the bromination of various substituted and unsubstituted aminoanthracene-9,10-diones.
Introduction
The brominated aminoanthracene-9,10-dione derivatives and with chlorobenzene, glacial acetic acid, methanol and also with
benzanthrone are widely used as intermediates for pharmaceut- molecular iodine as a catalyst. These reactions have various
icals [1-3], for medicinal applications [4], as dyes [5-9] and in disadvantages such as long reaction time (up to 24 h), high
Hg2+ ion sensors [10]. Although these bromo derivatives have a temperature (60 to 100 °C) and are accompanied by a mixture
wide range of applications, it is difficult to carry out their bro- of mono- and dibromo products. The reaction performed in
mination as the two carbonyl groups of aminoanthracene-9,10- glacial acetic acid at 100 °C resulted in 76% of the desired
dione deactivate the ring towards electrophilic substitution [11]. dibromo product in 6 h, along with the starting amine and some
Generally, the bromination of aminoanthracene-9,10-dione is byproducts. The long reaction time, drastic reaction conditions,
carried out in sulfuric acid [12-15] (20 to 98%) and nitroben- isomer formation and their separation (which is a very tedious
zene [16,17] at a high temperature (80 to 120 °C) with or and difficult task), and reduced bromine atom economy make
without a catalyst (like Cu or CuSO4) [18-21]. In all processes, these approaches economically unattractive. Again, in all the
hazardous molecular bromine is used as a bromine source [11- above processes, molecular bromine is used as the bromine
21]. Ghaieni et. al. [22,23] have reported bromination of source which reduces the bromine atom economy by 50% [24],
aminoanthracene-9,10-dione in a mixture of conc sulfuric acid as the HBr generated in the reaction is not used for further bro-
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Beilstein J. Org. Chem. 2014, 10, 921–928.
mination and also causes pollution of the environment. This metric titration after every 15 days (Table 1). It was found that
problem can be resolved by employing an oxidant in the reac- it retains its active oxygen content over a period of 45 days.
tion, which re-oxidizes the HBr and utilizes up to 90–95% There was no change observed in the physical appearance, too.
[25,26] of bromine. Various oxidants are used for this purpose This confirms the stability of nonanebis(peroxoic acid) at room
[27-30]. Compared to these commonly used oxidants the use of temperature.
peracids is likely to be limited due to their instability and the
resulting storage issues. These peracids are either have to be
Table 1: Stability study of nonanebis(peroxoic acid).
prepared in situ or they require cold storage conditions [31].
Entry
Days
% AOC
Finding that there is a need to develop a stable peracid, we
synthesized a stable, solid, aliphatic long chain peracid,
nonanebis(peroxoic acid). This peracid is easy to synthesize and
possesses very good properties [32] such as a high active
oxygen content (14.4%) and insusceptibility to shock. The
Differential Scanning Calorimeter (DSC) analysis data confirm
the non-shock-sensitive nature of nonanebis(peroxoic acid).
1
2
3
4
First day
14.2
14.0
14.2
14.3
After 15 days
After 30 days
After 45 days
Details are given in Supporting Information File 2, pages A further study was initiated with 1-aminoanthracene-9,10-
S35–S36. The most important advantage is that it is stable at dione (1a) as a substrate and KBr as a source of bromine.
room temperature. Thus it can be a good alternative for the Various solvents were screened (Table 2 entry 1–10) among
conventional peracids.
which, acetic acid was found to be more effective than other
solvents. It neutralizes the KOH formed during the reaction. To
In our previous work [11] (Scheme 1), we reported the use of validate the usability of other aliphatic acids, we carried out the
biodegradable deep eutectic mixtures as an alternative solvent reaction in formic, propionic and butyric acid. In the case of
to conventional solvents. The reaction selectively gives formic acid (Table 2, entry 8), during the addition of the peroxy
dibrominated product along with good recyclability of the acid, a strong exotherm reaction (temperature rose up to
solvent. The present work is an extension of our previous work 78–80 °C) was observed. To avoid the high temperature, it is
(Scheme 1). Here, we report the use of nonanebis(peroxoic necessary to add the peracid very slowly and cautiously with
acid) as an oxidant for bromination of aminoanthracene-9,10- external cooling. When propionic and butyric acids were used
dione. To the best of our knowledge, use of this stable, solid in the reaction, formation of other impurities was observed
peroxy acid and oxidative bromination of amino-anthracene- along with the product 2a. Considering all these factors, acetic
9,10-dione have not been reported in literature. This oxidation acid was selected as the best solvent for this transformation.
strategy allowed us to brominate various amino anthraquinone The study on peracid molar ratios showed that extra addition of
derivatives in good yield and at ambient temperature.
peracid does not influence the yield and reaction time (Table 2,
entry 13). When we carried out the reaction at a low tempera-
ture (15–18 °C), the rate of reaction remarkably slowed down.
Result and Discussion
The oxidant, nonanebis(peroxoic acid) was synthesized as per HPLC analysis shows 54% conversion after 12 h (Table 2, entry
the procedure reported in the literature [31]. To confirm the 14). Whereas, at 55 °C, the reaction shows 92% conversion at
stability of nonanebis(peroxoic acid), one sample was kept in a the expense of 1.25 equivalents of peroxide in 2 h (Table 2,
self-sealing bag at room temperature (30–35 °C). The active entry 15). No product formation was observed in the absence of
oxygen content (% AOC) of the sample was checked by iodo- peracid (Table 2, entry 16).
Scheme 1: Aliphatic peracid mediated bromination of aminoanthracene-9,10-dinone.
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Beilstein J. Org. Chem. 2014, 10, 921–928.
Table 2: Optimization of reaction conditions.a
Entry
Solvent
Oxidant (equiv)
Time (h)
Temp (°C)
Conversion (%)b Yield (%)c
1
ACN
1
12/5
12/5
12/5
12/5
12/5
12/5
2.30
2.00
2.30
2.30
12
rt/50-55
rt/50-55
rt/40-43
rt/50-55
rt/50-55
rt/50-55
rt
traces
traces
traces
traces
nr/traces
nr
0
2
DMF
1
0
3
DCM
1
0
4
ethanol
1
0
5
glycerol
1
0
6
water
1
0
7
acetic acid
formic acid
propionic acid
butyric acid
acetic acid
acetic acid
acetic acid
acetic acid
acetic acid
acetic acid
1
97
96
90
85
87
45
68
98
63
94
–
8
1
rt
85
9
1
rt
83
10
11
12
13
14
15
16d
1
rt
86
0.5
0.75
1.25
1
rt
25
12
rt
60
2.30
12
rt
95
15–18
50–55
rt/50–55
54
1.25
–
2
92
12/5
nr
aReaction conditions: 1-Aminoanthracene-9,10-dione (2.24 mmol, 1 equiv), KBr (4.48 mmol, 2 equiv), solvent 5 mL; rt: room temperature (30–32 °C);
nr: no reaction. bHPLC conversion; cisolated yield. dReaction carried out in the absence of oxidant. ACN: acetonitrile; DCM: dichloromethane.
To confirm the efficiency of nonanebis(peroxoic acid), bro- derivatives of anthracene-9,10-dione. In most cases, under stan-
mination was carried out using commercially available dard conditions, the reaction proceeded smoothly at room
oxidants. The results obtained are summarized in Table 3. It temperature in few hours. The unsubstituted amine derivatives
was found that one equivalent of nonanebis(peroxoic acid) 1a–1f (Table 4, entries 1–6) and amine with an electron
(contains two active oxygen atoms) (Table 3, entry 1) was suffi- donating substituent at the para-position (1g, Table 4, entry 7)
cient to promote the dibromination of 1-aminoanthracene-9,10- were brominated at room temperature and gave an excellent
dinone (1a) smoothly at room temperature and in less time. yield of the desired product. Whereas, the amine with an elec-
Amongst the other oxidants, Oxone (Table 3, entry 2) shows tron withdrawing substituent at para-position (1h, Table 4,
94% conversion of 1a in 2 h. In case of 50% Hydrogen entry 8) or N-alkylated amines 1i and 1j (Table 4, entries 9 and
peroxide (Table 3, entry 3), more than 7 equivalents of oxidant 10) showed very low conversion at room temperature even after
were required with successive addition. The urea hydrogen carrying out the reaction for 12 h. The rate of bromination of
peroxide shows moderate conversion in 20 h (Table 3, entry 6). these derivatives (1h–1j) can be increased by carrying out bro-
The other diperoxy acids like hexanebis(peroxoic acid) mination at 50–55 °C. The electron deficient arene 1k (Table 4,
(Table 3, entry 7) and dodecanebis(peroxoic acid) (Table 3, entry 11) also undergoes bromination at 50–55 °C. In case of
entry 8) have shown poor conversion under present reaction substrates like 1,4-diaminoanthracene-9,10-dione and 1-amino-
conditions. The bromination of 1a using performic acid showed 4-hydroxyanthracene-9,10-dione, the protocol was found to be
traces of conversion while 18% conversion was observed in unsuccessful. It was surmised that in the presence of oxidant
peracetic acid after 20 h (Table 3, entries 9 and 10). The other these substrates form a diimine type product (similar to oxida-
oxidants (Table 3, entries 4, 5, 11, 12) showed moderate to poor tive hair dye mechanism) [33], which makes the ring unreac-
conversion.
tive towards electrophilic substitution.
The optimized conditions have a broad substrate scope which Since Oxone and 50% hydrogen peroxide showed good results
was investigated by examining various amino substituted with substrate 1a, we have checked the applicability of these
923

Beilstein J. Org. Chem. 2014, 10, 921–928.
Table 3: Comparison with commercially available oxidants.a
Entry
Oxidant
Oxidant (equiv)
Time (h)
Conversion (%)b
1
nonanebis peroxoic acid
Oxone
1
2
>7
2
2
2
1
1
2
2
2
2
2.3
2
97
94
86
20
3
2
3
50% H2O2
20
20
20
20
20
20
20
20
20
20
4
sodium perborate
ammonium persulfate
urea hydrogen peroxide
hexanebis(peroxoic acid)
dodecanebis(peroxoic acid)
performic acid
5
6
85
20
58
traces
18
43
15
7
8
9
10
11
12
peracetic acid
m-CPBA
70% TBHP
aReaction conditions: 1-Aminoanthracene-9,10-dinone (0.5 g, 2.24 mmol), KBr (0.53 g, 4.48 mmol), oxidant (1 to 7 equiv), acetic acid 5 mL; tempera-
ture: room temperature (30–32 °C); reaction monitored on TLC. bHPLC conversion.
two oxidants for the bromination of some substrates listed in higher temperature when 50% hydrogen peroxide was used as
Table 4. The bromination of substrate 1b using Oxone as an an oxidant. This study demonstrates the superiority of
oxidant required 14 h for complete conversion at room tempera- nonanebis(peroxoic acid) under the present protocol.
ture. Whereas, the substrate 1g did not show complete conver-
sion in 24 h at room temperature as well as at 50–55 °C. The It was surmised that, the oxidant nonanebis(peroxoic acid)
N-alkylated substrates such as 1i, 1j and the substrate 1k oxidizes the KBr to Br+ (Scheme 2). During this process, KOH
showed poor conversion (product formed in tracess) even at a is formed, which is neutralized by the acetic acid. The bromo-
Table 4: Bromination of various aminoanthracene-9,10-dione derivatives and benzanthrone.a
mp (°C)
Time/Temp
(h/°C)
Yield
(%)b
HPLC
(%)
Entry
Reactant
Product
Obs.
(°C)
Rep.
(°C)
1
2.30/rt
2.00/rt
92
97
97
99
223–224 224–226 [11]
1a
1b
2a
2b
2
235–237
238 [17]
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Beilstein J. Org. Chem. 2014, 10, 921–928.
Table 4: Bromination of various aminoanthracene-9,10-dione derivatives and benzanthrone.a (continued)
3
4
3.00/rt
2.00/rt
93
96
98
99
246–248 249–250 [11]
1c
1d
2c
2d
250
250 [34]
5
2.00/rt
87
98
209–210
–
1e
2e
Decomp.
>250 [11]
6
7
3.00/rt
3.00/rt
80
86
99
99
263–265
1f
2f
177–178 174–176 [11]
1g
2g
8
3.00/50–55
83
99
246–248
247 [11]
1h
2h
9
2.30/50–55
86
93
98
99
153–154 154–158 [11]
1i
2i
10
2.30/50–55 °C
136–137
–
1j
2j
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Beilstein J. Org. Chem. 2014, 10, 921–928.
Table 4: Bromination of various aminoanthracene-9,10-dione derivatives and benzanthrone.a (continued)
11
3.00/50–55 °C
86
99
177
177 [35]
1k
2k
aReaction conditions: Aminoanthracene-9,10-dione (0.5 g, 1 equiv); acetic acid (5 mL); KBr [1 equiv (for entries 2, 7, 8, 11); 2 equiv (for entries 1, 3, 4,
5, 9, 10); 4 equiv (for entry 6)]; nonanebis(peroxoic acid) [0.5 equiv (for entries 2, 7); 0.8 equiv (for entries 8, 11); 1 equiv (for entries 1, 3, 4, 5); 1.2
equiv (for entries 9,10); 2 equiv (for entry 6)]; rt: room temperature (30–32 °C); bisolated yield.
Scheme 2: Plausible mechanism for the bromination of aminoanthracene-9,10-dione [36,37].
nium ion thus formed reacts with the amine to give the bromi- Conclusion
nated product. In case of unsubstituted amines, ortho-bro- Thus, we can summarize that we have developed a simple, effi-
mination occurs first, while in case of N-substituted amines cient and convenient process for the bromination of aminoan-
para-bromination takes place first [22].
thracene-9,10-dione using nonanebis(peroxoic acid) as an
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Beilstein J. Org. Chem. 2014, 10, 921–928.
oxidant. The bromination reaction proceeds under mild condi- 10% sodium bicarbonate solution to neutralize the acids. The
tions with high yield and purity. The peracid used here is stable, solid obtained was filtered and washed with water till neutral
safe and easy to handle and thus can be a good attractive pH was obtained. The crude product was purified by column
alternative to the conventional peracids. Further study on chromatography on a silica gel with hexane/ethyl acetate (95:5)
nonanebis(peroxoic acid) is under progress.
as an eluent to give purified product 2.
Experimental
Scale-up study
General information
The reaction of 1-aminoanthracene-9,10-dione with KBr in
All products were confirmed by melting point, FTIR spec- acetic acid and nonanebis(peroxoic acid) as an oxidant was
troscopy, 1H NMR spectroscopy and mass spectrometry. Purity scaled-up to 10 g to understand the functioning of the method
was checked by HPLC using acetonitrile/methanol (90:10) on a larger scale. The reaction yields 96% desired dibromo
mobile phase and silica column C18. All melting points are product without formation of any isomer in 2.30 h at room
uncorrected and are presented in degree Celsius. 1H NMR temperature. From this it was clear that the present protocol
(400 MHz) spectrum were recorded using Varian spectraprobe shows good applicability on larger scale also.
and Bruker 400 ultrashield (Advance 400 NMR spectrometer)
and chemical shifts are expressed in δ ppm using TMS as an
Supporting Information
internal standard. Mass spectral data were obtained with a
Micromass Q-TOF spectrometer. The DSC analysis was done
Supporting Information File 1
using a DSC Q100 V9.9 Build 303 (Universal V4.5A TA
Instrument), ramp 10.00 °C/min to 300.00 °C, flow rate:
50.0 mL/min.
Characterization details for all the products in Table 4.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-10-90-S1.pdf]
Supporting Information File 2
Procedure for the preparation of nonanebis(peroxoic acid):
In 250 mL round bottomed flask equipped with a mercury
sealed stirrer, 10 g of nonanedioic acid (0.0531 mol) was
dissolved in 95% sulfuric acid (25 g, 0.255 mol) with good stir-
ring. The reaction mass was cooled to 15 °C using an ice-water
bath. To this 65% hydrogen peroxide (11 g, 0.323 mol) was
added drop-wise while maintaining the internal temperature at
15 to 20 °C. After the addition, the reaction mass was further
stirred for 5 h at 15 to 20 °C. Then, 50 mL half saturated
aqueous ammonium sulfate solution (35 g/100 g water) was
FTIR, mass and 1H NMR spectra of all products in Table 4,
Differential Scanning Colorimetric (DSC) analysis and
calculations for shock sensitivity of nonanebis(peroxoic
acid), HPLC analysis details, procedure for the detection of
% active oxygen content (%AOC).
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-10-90-S2.pdf]
added to the reaction mass at 0 °C. The white solid was filtered Acknowledgements
and washed with cold half saturated ammonium sulfate solu- Authors are thankful to the Institute of Chemical Technology
tion (4 × 10 mL). The crude product obtained was dried under and UGC-CAS for providing financial assistance and SAIF IIT
vacuum at room temperature to give the final product (9.2 g, Bombay for recording Mass.
78% yield).
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