Table salt as a catalyst for the oxidation of aromatic alcohols and amines to acids and imines in aqueous medium: Effectively carrying out oxidation reactions in sea water

Article abstract of DOI:10.1039/c9gc00497a

A simple, efficient, sustainable and economical method for the oxidation of alcohols and amines has been developed based on chloride, a sea abundant anionic catalyst for the practical synthesis of a wide range of carboxylic acids, ketones and imines. Oxidation of aromatic alcohols was carried out using NaCl (20 mol%) as the catalyst, NaOH (50 mol%) and aq. TBHP (4 equiv.) as the oxidant in 55-92% isolated yields. Oxidation of aromatic amines to imines was achieved by using only 20 mol% of NaCl and aq. TBHP (4 equiv.) in 32-93% isolated yields. The chlorine species formed during the reaction as the active oxidation catalyst has been identified as ClO₂^- for alcohols and ClO^-/ClO₂^- for amines by control experiments. This method is mostly free from chromatographic purification, which makes it suitable for large-scale synthesis. We have scaled up to 30 gram scale the synthesis of carboxylic acids and imines in good yields and have also carried out efficiently this new method using filtered sea water as the solvent and catalyst.

Full text of DOI:10.1039/c9gc00497a

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Hazra, A. K.
Kushawaha, D. Yadav, P. Dolui, M. Deb and A. J. Elias, Green Chem., 2019, DOI: 10.1039/C9GC00497A.
This is an Accepted Manuscript, which has been through the
Volume 18 Number
7 7 April 2016 Pages 1821–2242
Royal Society of Chemistry peer review process and has been
accepted for publication.
Green
Chemistry
Accepted Manuscripts are published online shortly after
Cutting-edge research for a greener sustainable future
www.rsc.org/greenchem
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1463-9262
CRITICAL REVIEW
G. Chatel et al.
Heterogeneous catalytic oxidation for lignin valorization into valuable
chemicals: what results? What limitations? What trends?
rsc.li/green-chem

Please do not adjust margins
Page 1 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C9GC00497A
Journal Name
COMMUNICATION
Table salt as catalyst for oxidation of aromatic alcohols and
amines to acids and imines in aqueous medium: Effectively
carrying out oxidation reactions in sea water
Received 00th January 20xx,
Accepted 00th January 20xx
Susanta Hazra, Ajay Kishor Kushawaha$, Deepak Yadav$, Pritam Dolui, Mayukh Deb and Anil J.
Elias*
DOI: 10.1039/x0xx00000x
www.rsc.org/greenchem
A simple, efficient, sustainable and economical method for oxidation of
alcohols and amines has been developed based on chloride, a sea
abundant anionic catalyst for the practical synthesis of a wide range of
carboxylic acids, ketones and imines. Oxidation of aromatic alcohols was
carried out using NaCl (20 mol%) as catalyst, NaOH (50 mol%) and aq.
TBHP (4 equiv.) as oxidant in 55-92% isolated yields. Oxidation of aromatic
amines to imines was achieved by using only 20 mol% of NaCl and aq.
TBHP (4 equiv.) in 32-93 % isolated yields. The chlorine species formed
during the reaction as the active oxidation catalyst has been identified as
Previous Reports
O
R'
O
Cl2/Me2S
(COCl)2/DMSO
R
R'
R
R'
R
-78 o
Et3N
C
OH
-25 oC to 0 o
Et3N, CCl4
C
By D. Swern in 1978
(Swern Oxidation)
By E. J Corey in 1972
Where R' =H, aryl
O
O
TEMPO/Cl2
Cat. TEMPO/KBr
R
OH
O
R
H
R
H
DCM
DCM, Na2CO3
By Anelli-Montonari
in 1987
NaHCO3, NaOCl
By H. R. Bjørsvik
in 2002
X= O
Cat. NaCl/NaOH
Present Work
–
ClO2for alcohols and ClO–/ClO2 for amines by control experiments. This
Where R' = OH, Me, Ph, n-Bu
R'
R'
R
aq. TBHP, 70 o
C
method is mostly free from chromatographic purification, which makes it
suitable for large-scale synthesis. We have scaled up to 30 gram scale the
synthesis of carboxylic acids and imines in good yields and have also
carried out efficiently this new method using filtered sea water as solvent
and catalyst.
R
XH
X= NH
Cat. NaCl
R'
R'
R= Aryl,
Hetero aryl
N
R
R
aq. TBHP, 70 o
C
R'= H
Scheme 1:Existing methods for the oxidation of alcohols to carbonyl
compounds using Cl2 or chlorine based reagents.
A recent trend in catalysis has been directed towards finding
alternatives to traditional catalysts based on precious metals such
as Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, or Au and toxic elements such as Hg
and Pb by utilizing the more earth abundant catalysts based on
cations from the s and p blocks and first row transition metals.[1] As
the potential benefits to society and to chemists are many, a new
area of catalysis using such metal and metalloid cations, termed
‘earth abundant catalysis’ has come into prominence.[2] Equally
significant among recent developments in catalysis are metal free
catalysts, mostly based on I2 and low-valent main group
oceans has a salinity of approximately 3.5% which means that for
every liter (1000 mL) of sea water there are ~35 grams of salts
(mostly, but not entirely sodium chloride) present in it.[6] Earth’s
oceans together contain about 2.6x1016 metric tons of chlorine as
chloride which makes it the most abundant ion present in sea
water.[5,6] Although homogeneous catalysis based on the
iodine/hypervalent iodine platforms have matured into viable
synthetic methods[3] and bromine has also recently entered
homogeneous catalysis,[7] catalysis based on chlorine has virtually
remained in its infancy mostly due to risks involved in operation
due to its gaseous and toxic state. Previous reports on the use of
chlorine (Cl2) or chlorine based oxidants such as NaOCl for oxidation
of alcohols are presented in scheme 1.[8] However, all the existing
methods involving Cl2 or hypervalent chlorine compounds make use
of organic solvents, highly reactive and volatile reagents and often
involve tedious work up procedures which generate harmful by-
products. Importantly, most of these oxidation reactions of alcohols
using Cl2 stop at the aldehyde stage. Therefore, additional
oxidation steps are required to obtain the desired carboxylic
acids. One of the most noticeable examples of this reactivity is
the “Pinnick oxidation” which requires excess amount of
NaClO2 and a sacrificial alkene to scavenge the hypochlorite
by-product of the reaction.[8i] On the other hand, the direct
compounds.[3,4] Despite, the diversity shown by I2 in catalysis
3b, 3i]
ranging from oxidation,[3a,
C-O, C-N, C-S and C-C bond
formation via cross dehydrogenative coupling (CDC) reactions[3c-f]
and even olefin metathesis,[3j] it fails to be classified as ‘abundant’
due to its inherently poor natural abundance.[5] In contrast,
catalysis using the sea abundant anion, chloride and the direct use
of its source namely sea water in homogeneous catalysis has largely
remained unexplored. On an average, sea water in the world's
a. Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New
Delhi-110016, India, Email: eliasanil@gmail.com,Fax: +91-11-26581102; Tel: +91-
11-26591504. $ These co-authors have contributed equally.
† ElectronicSupplementary Information (ESI) available: DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 2 of 7
COMMUNICATION
Journal Name
oxidation of alcohols and amines to acids, ketones and imines with the desired imine product. Therefore, several rVeiaewctAiortnicsle Ownelirnee
DOI: 10.1039/C9GC00497A
has been a long standing challenge for synthetic chemists, carried out to optimize the reaction conditions for oxidation of
particularly for designing new water soluble catalysts.[9] A few amines to imines. After significant exploration (see Supporting
recent efforts have been focused to realize direct Information, tables S8-S12), we observed that these reactions do
transformation of alcohols and amines to corresponding acids, not require the base NaOH and 20 mol % NaCl with 4 equiv. of aq.
ketones and imines using transition metal based catalysts and TBHP is best suited for the reaction with high (98%) selectivity for
water as the solvent.[10] Catalytic methods which are transition imines (Scheme 3). Although relatively more expensive, NaBr is
metal/nanoparticle based and stoichiometric methods equally good as catalyst for these transformations under identical
involving high boiling ethers using air as the oxidant have also reaction conditions (see Supporting Information, tables S1, S8).
been reported recently for oxidation of alcohols.[11] However,
NaCl (20 mol%)
NH2
N
these methodologies still have drawbacks with reference to
work up procedures and cost effectiveness for large scale
production in industries. Hence, new methods using abundant
and inexpensive catalysts and water as solvent for direct
oxidation of alcohols to carboxylic acids or amines to imines
are highly desirable. Sodium chloride has been reported as a
useful additive for direct and fast palladium catalyzed cross-
coupling reactions involving organolithium reagents.[12] Herein
we report the first use of NaCl as catalyst for the oxidation of
alcohols to carboxylic acids or ketones and amines to imines in
purely aqueous medium. Moreover, we demonstrate that sea
water itself can act as catalyst and solvent for these oxidation
reaction.
aq. TBHP (4 equiv.)
OMe
MeO
MeO
H2O, 70 o
20 h
C
2b
2
93 %
Scheme 3: Optimized reaction conditions for oxidation of primary amines
to imines. Reaction conditions: 4-methoxy benzyl amine 2 (0.5 gm, 3.64
mmol), NaCl (0.72 mmol, 42 mg), TBHP (70% in water, 14.56 mmol, 1.32
gm) and 1 mL H2O.
After optimizing the reaction conditions, we explored the
substrate scope for the reaction (Figures 1 and 2). The reaction
was extended to compounds having electron donating as well
as electron withdrawing substituents on the aryl ring of
alcohols and amines. Both gave >80% yields of desired oxidized
products. Under identical conditions, an aliphatic alcohol was
converted to its ester derivative (Figure 1, 1p). We have also
carried out the reaction with two different amines to obtain
In our previous study on the oxidation of alcohols to acids using
–
I2/TBHP, we observed that in-situ generated iodite (IO2 ) is the
active species for the oxidation in aqueous medium.[3i] Molecular
iodine first reacted with NaOH to generate hypoiodite (IO–) which
–
was readily oxidized to iodite (IO2 ) in the presence of aq. TBHP.
NaCl (20 mol%)
NaOH (50 mol%)
O
R
OH
However, potassium iodide (KI) was also able to catalyze the
reaction in the presence of TBHP albeit in low yields (48%). This
result indicated that TBHP has the potential also to oxidize iodide
(I) to molecular iodine (I2) which further reacted with NaOH to
form hypoiodite (IO–). While our attempts to replace I2 by Cl2 in
oxidation reactions using TBHP as co-oxidant was not successful, we
were able to use the ubiquitous and easily handled NaCl instead of
Cl2 for the generation of hypervalent chlorine species using TBHP as
the oxidant. We started our investigation using benzyl alcohol as
the model substrate and NaCl as the catalyst. Initially, we obtained
only 43 % yield of benzoic acid using 10 mol% NaCl, 20 mol% NaOH
and 4 equiv. of aq. TBHP. This finding promoted us to explore the
scope of the reaction by varying the reaction parameters. After
detailed studies (see Supporting Information, tables S1-S7), we
were able to maximize the yield of benzoic acid up to 92% using 20
mol% NaCl, 50 mol% NaOH and 4 equiv. of aq. TBHP (Scheme 2).
OH
R
aq. TBHP (4 equiv.)
70 oC, 10-12h
1
1a-z
O
O
O
O
OH
OH
OH
OH
H3
C
O2N
MeO
1d, 86%
1b, 90%
1c, 92%
Cl
1a, 92%
O
O
O
O
OH
OH
OH
OH
Br
F3C
CH3
Cl
1g, 85%
1h, 90%
1f, 85%
1e, 87%
O
O
O
O
OH
O
OH
OH
OH
N
CH3
OMe
1k, 78
1l, 89%
1j, 86%
1i, 88%
O
O
O
O
O
OH
O
()4
()4
OH
HO
OH
S
1o, 85%a
1n, 70%a
1p, 67%
1m, 72%
O
O
O
O
O
CH3
CH3
CH3
CH3
NaCl (20 mol%)
Cl
NaOH (50 mol%)
Me
MeO
OH
1t, 85%
OH
1s, 90%
1r, 92%
1q, 91%
aq. TBHP (4 equiv.)
O
O
H2O, 70 o
10-12 h
C
O
1a
O
1
92 %
MeO
MeO
1x, 92
1u, 90%
1w, 91%
1v, 88%
Scheme 2: Optimized reaction conditions for oxidation of benzyl
alcohol. Reaction conditions: Benzyl alcohol 1 (0.5 gm, 4.6 mmol), NaCl
(0.92 mmol, 53 mg), NaOH (2.3 mmol, 92 mg), TBHP (70% in water,
18.4 mmol, 1.65 gm) and water (0.2 ml, 3equiv.), 70 oC for 12h.
O
1y, 55%
However, under identical reaction conditions, primary amines gave
a mixture of products. 1H and 13C NMR studies of the reaction
mixture indicated the presence of aldehyde, acid and amide along
Figure 1: Yields of acids and ketones obtained by oxidation of alcohols
using Cl as catalyst. Reaction conditions: Alcohols (5 mmol), NaCl (1
mmol), NaOH (2.5 mmol), TBHP (70% in water; 20 mmol), 70 °C, 10–
16 h. aFor compounds 1n and 1o, NaCl (40 mol%), NaOH (1 equiv.),
TBHP (70% in water; 8 equiv.) were used. Isolated yields are given for
all substrates.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 7
Green Chemistry
Please do not adjust margins
Journal Name
COMMUNICATION
unsymmetrical imines (Figure 2, 5a-5e). However, the yields of chloride/bromide (see Supporting Information, page S16). The
View Article Online
DOI: 10.1039/C9GC00497A
unsymmetrical imines were relatively low (25-43%) and were salinity of most seawater, free from land influences, varies
obtained along with the symmetrical imines. The better between 31 and 38 gm/L, with average seawater salinity
selectivity for symmetrical imines may be due to the higher around 35 gm/L.[6] The major constituents of sea water
nucleophilicity of benzyl amines with respect to aniline and the calculated by recent measurements (% of mass fraction of
2–
poor water solubility of octylamine.
total ions) are Cl–(55.03%), Na+ (30.66%), SO4 (7.71%), Mg2+
(3.65%), Ca2+ (1.17%), K+ (1.13%), Br– (0.19%).[6] As shown in
scheme 4 oxidation of alcohols and amines have been
effectively carried out using sea water. A higher amount of
NaOH is required when sea water is used instead of pure NaCl
(80 mol% instead of 50 mol%).
For symmetrical imines
NaCl (20mol%)
Aq. TBHP (4 equiv.)
H2O, 65-70oC
20-24h
R1
N
R1
R1
NH2
(2a-j)
2
N
N
2c
90%
N
To illustrate the practical utility of our methodology using NaCl, we
have carried out a large scale oxidation (30 gm) of benzyl alcohol as
well as benzyl amine and we were able to isolate the desired
carboxylic acid and imine in 92% and 89% yields respectively (see
Supporting Information, page S13). As the products are mostly
solids (acids) or semi-solids (imines) and the by-product is mainly t-
BuOH, which is a low boiling liquid (b.p 82.2 oC) the two can be
easily separated from the reaction mixture. Most importantly, aq.
TBHP is industrially synthesized from t-BuOH by reaction with H2SO4
and H2O2.[13] Therefore, one can easily reuse the by-product (t-
BuOH) for making TBHP or as solvent by a simple reaction setup
which makes this method economical from an industrial point of
view (see Supporting Information, page S13).
MeO
OMe
F
F
2b
93%
2a
92%
Cl
Cl
OMe
N
F3C
CF3
MeO
N
N
2f
87%
2d
2e
85%
89%
N
N
N
Cl
S
Cl
2g
88%
S
i
2
2h
70%
91%
N
2j
76%
For unsymmetrical imines
NH2
NaCl (20mol%)
aq. TBHP (4 equiv.)
65-70oC
R1
N
R
R1
NH2 +
NH2
(5a-e)b
()6
or
O
R= aniline,
octylamine
NaCl (20 mol%)
NaOH (50 mol%)
2
3
4
20-24h
OH
OH
1.
Cl
aq. TBHP (4 equiv.)
70 oC, 12h
N
N
Normal: 92%
N
5c
32%
5b
5a
MeO
With TEMPO: 90%
With BHT: 5%
43%
37%
With ascorbic acid: 0%
O
O
N
5e
32%
O
N
MeO
MeO
5d
6
25%
Isolated as major
product in case of BHT
Figure 2: Yields of imines obtained from amines using Cl as catalyst.
Reaction conditions: Primary amines 2(5 mmol), NaCl (1 mmol), TBHP
(70% in water; 20 mmol), water 1 mL, 65-70 °C, 20–24 h. bFor compounds
5a-5e3 equiv. aniline or octylamine was used. NMR yields are given and
reactions were carried out with out external water.
O
O
NaCl (20 mol%)
NaOH (50 mol%)
OH
H
2.
MeO
MeO
aq. TBHP (4 equiv.)
70 oC, 12h
Normal : 90%
With TEMPO: 90%
With BHT: 88%
O
X (2 equiv.)
OH
OH
3.
We explored the possibility of carrying out the reaction in sea
water (Scheme 4). Sea water was collected from Kanyakumari
(The southern-most tip of India). Analysis of this sea water
using standard AgNO3 solution (Mohr’s Method) indicated that
the sample of sea water contains 39.73 gm/L of
H2O, RT-70 o
12h
C
X= NaOCl, yield: 0%
X= NaClO3, yield: 0%
O
NaClO2 (X equiv.)
OH
OH
4.c
OH
H2O, RT-70 o
12h
C
X= 0.1, yield: 5%
X= 1, yield: 48%
X= 2, yield: 62%
Sea Water (1.5 mL)a
NaOH (80 mol%)
O
O
NaCl (20 mol%)
NaOH (50 mol%)
OH
OH
OH
5.
X
aq. TBHP (4 equiv.)
70 oC, 12 h
X
X= H, 1a 81 %
X= Me, 1b 67%
X= OMe, 1c 67%
X= Br, 1e 65%
6M TBHP in decane
(4 equiv.)
1
90%
70 oC, 12h
Sea Water (2 mL)a
N
NH2
Y
Y
Y
aq. TBHP (4 equiv.)
70 oC, 20 h
Y= H,
92 %
Y= OMe, 2b 93%
Y = F, 2c 90%
2a
Scheme 5: Control experiments carried out for mechanistic studies for oxidation
of alcohols. c Remaining part was unreacted alcohol.
2
Scheme 4: Optimized reaction conditions for oxidation of alcohols and
a
amines using sea water as catalyst and reaction medium. Reactions
To understand the reaction mechanism and to identify the active
chlorine species for oxidation of alcohols to acids, several control
were carried out in 1gm scale.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 4 of 7
COMMUNICATION
Journal Name
experiments were carried out (Scheme 5). Although, BHT (butylated
hydroxytoluene) and ascorbic acid both inhibited the reaction,
there was no significant decrease in yield in case of intermediate
aldehyde under the standard reaction conditions (Scheme 5, entry
1, 2). On carrying out the oxidation of benzyl alcohol in presence of
BHT, we were able to isolate the peroxide 6 instead of the desired
benzoic acid which suggested that a free radical pathway is involved
in the first step of the oxidation reaction.[7e] However, there was no
change in the yield when TEMPO (2, 2, 6, 6-tetramethylpiperidine-
N-oxyl) was used as radical inhibitor in both the cases (Scheme 5,
entry 1, 2). This may be due to the catalytic activity of TEMPO in
View Article Online
.

tBuO-OH + Cl
+ tBuO + OH
(1)
Cl2
ClO
DOI: 10.1039/C9GC00497A
H2O
OH
(2)
Cl2
TBHP
tBuO
+
TBHP


ClO
tBuO-OH
(3)
(4)
ClO3
ClO2
.
.
+ tBuOH
t-BuO-O
.
or TBHP
t-BuOH
t-BuO
or
.
.
OH
R
t-BuO-O
OH
R
t-BuOH
IM1

[CIO2
]
8f]
presence of the in-situ generated NaOCl.[8c, Neither equal nor
A
P
active catalyst
H
B
T
excess amounts of NaCl could catalyze this oxidation reaction in the
absence of base and oxidant. In addition, stoichiometric amount of
NaOCl was unable to oxidize alcohol to the corresponding
carboxylic acid (Scheme 5, entry 3). This result indicates that
hypochlorite (ClO¯) is not the active catalyst for this transformation.
Since, chlorate (ClO3¯) can also be formed in the reaction medium
(eqn (3) Scheme 7), we carried out separate reactions of alcohol by
using excess (2 equiv.) of NaClO3 (Scheme 5, entry 3). Excess
amount of NaClO3 was also unable to oxidize the alcohols to
carboxylic acids. This result ruled out the possibility of chlorate
(ClO3¯) as the possible active catalyst for this transformation. Our
controlled experiments clearly suggest that in-situ formed chlorite
(ClO2¯) is possibly the active catalyst for this oxidation reaction
(Scheme 5, entry 4). In our previous work using I2/TBHP, the
reactions were found to stop at the aldehyde stage under
anhydrous reaction conditions which suggested that the aldehyde
water shift (AWS) reaction was involved for aldehyde to acid
O
ClO
H2O
ClO
O
R
H
O
R

ClO2
O
H
R
O
Cl
IM2
O
B
t-BuOH
NH2
R

[ClO/CIO2
]
active catalyst
P
H
B
T
CI
–
[3i]
H2O/CIO
conversion in the presence of iodite (IO2 ).
However, in the
Cl
N
R
present study direct oxidation of alcohol to acid is also possible
under anhydrous reaction conditions with 90% yield of the desired
carboxylic acid (Scheme 5, entry 5). Moreover, yields of carboxylic
acids were found to decrease in the presence of excess amount of
water which indicated that AWS reaction is less favoured under
these catalytic conditions.
We have also carried out control experiments to find out the
possible reaction mechanism and active species for oxidation of
amines to imines (Scheme 6). In our previous work on primary
amine oxidation using water soluble Co(bpb) complex and
ferrocenium as catalysts, we observed that both the reactions
follow the radical pathway.[10l-m] However, in the present study
there was no significant change in the yields in presence of radical
inhibitors (Scheme 6).
H
IM3
R
NH2
-NH3
O
H2N
HN
R
H
R
2O
R
NH
IM4
GC, m/z 135.0
H
R
NH2
-H2O
R
R
N
R
Scheme 7: Possible catalytic cycles and generation of active catalyst for the
oxidation of alcohols to carboxylic acids (A) and amines to imines (B) in
water.
(Scheme 7). The first step involves the formation of molecular
chlorine (Cl2) and t-BuO• radical from NaCl in presence of TBHP
(eqn (1), Scheme 7), which immediately reacts with base or
water to form hypochlorite. Next, TBHP oxidizes hypochlorite
(ClO¯) to the active catalyst chlorite (ClO2¯) (eqn. (3), Scheme
NaCl (20 mol%)
N
NH2
1.
OMe
MeO
aq. TBHP (4 equiv.)
70 oC, 20h
MeO
Normal :92%
With TEMPO: 80%
With BHT : 75%
–
7). The ClO2 species oxidizes the alcohol to aldehyde or
N
NH2
ketone and itself gets reduced to ClO– in the presence of t-
X (1 equiv.)
2.
MeO
H2O, RT-70 o
20h
C
–
OMe
MeO
BuO• or t-BuO-O• radical. Next, ClO2 attacks the carbonyl
X = NaOCl , yield: 50%
X= NaClO2, yield: 25%c
centre under these reaction conditions and results in the
formation of a tetrahedral intermediate IM2 (Scheme 7A).
Following this, ClO2 oxidizes aldehyde to the carboxylate salt
Scheme 6: Control experiments carried out for mechanistic studies for
–
c
oxidation of primary amine. NaClO2 reacts with amine vigorously even at
RT.
and regenerates ClO–. Similarly, primary amine reacts with
ClO– or ClO2– to form N-chloroamine IM3 (Scheme 7B) which is
readily converted to imine IM4 which was confirmed by gas
chromatography (GC, m/z 135.0). [10m] Hydrolysis of this imine
intermediate IM4 induced by H2O with the elimination of a
molecule of NH3 results in the formation of benzaldehyde,
which reacts with another benzylamine molecule to generate
Based on our observations and related studies from the
literature,[3,7] possible catalytic cycles have been proposed
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 7
Green Chemistry
Please do not adjust margins
Journal Name
COMMUNICATION
Liu, K. N. Betz, A. Fedorov, B. M. Stoltz, R. H. GrVuiebwbAsr,tiNcleaOtunlrinee,
2015, 518, 80-84; (e) R. M. Bullock, Chem, 2017, 2, 443-447;
(f) P. Du and Richard Eisenberg, EnergDyOEIn: 1v0ir.1o0n3.9S/Cci9.G, 2C0010429,75A,
6012–6021; (g) D. Wang and D. Astruc, Chem. Soc. Rev.,
2017, 46, 816-854; (h) M. R. Friedfeld, H. Zhong, R. T. Ruck,
M. Shevlin and P. J. Chirik, Science, 2018, 360, 888–893.
(a) M. S. Yusubov and V. V. Zhdankin, Resource-Efficient
Technologies, 2015, 1, 49-67; (b) A. Yoshimura, V. V.
Zhdankin, Chem. Rev., 2016, 116, 3328-3435; (c) Y. –M. Ren,
C. Cai and R. –C. Yanga, RSC Adv., 2013,3, 7182-7204; (d) D.
Liu and A. Lei, Chem. Asian J., 2015, 10, 806-823; (e) X. –F.
Wu, J. –L. Gonga and X. Qia,Org. Biomol. Chem.,2014,12,
5807-5817; (f) P. T. Pravatkar, R. Manetsch andB. K.
Banik,Chem. Asian J., 2019, 14, 6-30; (g) Y. Zi, Z. –J. Cai, S. –Y.
Wang and S. –J. Ji, Org. Lett., 2014, 16, 3094-3097; (h) P. S.
Volvoikar and S. G. Tilve, Org. Lett., 2016, 18, 892-895; (i) S.
Hazra, M. Deb and A. J. Elias, Green Chem., 2017, 19, 5548-
5552; (j) U. P. N. Tran, G. Oss, M. Breugst, E. Detmar, D. P.
Pace, K. Liyanto and T. V. Nguyen, ACS Catal., 2019, 9, 912-
919.
(a) S. K. Mondal and H. W. Roesky, Acc. Chem.
Res., 2012, 45, 2, 298-307; (b) T. J. Hadlington, M. Driess and
C. Jones, Chem. Soc. Rev., 2018, 47, 4176-4197; (c) S. Yadav,
S. Saha and S. S. Sen, ChemCatChem., 2016, 8, 486-501; (d)
M. K. Sharma, M. Ansari, P. Mahawar, G. Rajaraman and S.
Nagendran, Dalton Trans., 2019, 48, 664–672; (e) M. K.
Sharma, S. Sinhababu, G. Mukherjee, G. Rajaraman and S.
Nagendran, Dalton Trans., 2017, 46, 7672-7676; (f) S. V. S.
N. Swamy, M. K. Bisai, T. Das and S. S. Sen, Chem.Commun.,
2017, 53, 6910-6913; (g) M. K. Bisai, S. Pahar, T. Das, K.
Vanka and S. S. Sen, Dalton Trans., 2017, 46, 2420-2424.
J. W. Morgan and W. Anders, Proc. Natl. Acad. Sci., 1980,
77, 6973-6977.
(a) S. F. E. Boerlage, Desalination and Water Treatment,
2012, 42, 222-230; (b) F. J. Millero R. Feistel, D. G. Wright
and T. J. McDougal, Deep-Sea Research I, 2008, 55, 50-72.
(a) P. Becker, T. Duhamel, C. Martinez, K. Muñiz, Angew.
Chem. Int. Ed.,2018, 57,5166-5170; (b) P. Chavez, J. Kirsch, C.
H. Hçvelmann, J. Streuff, M. Martínez-Belmonte, E. C.
Escudero-Adμn, E. Martin, K. Muñiz, Chem. Sci.,2012, 3,
2375-2378; (c) M. Ochiai, K. Miyamoto, T. Kaneaki, S. Hayashi
and W. Nakanishi, Science, 2011, 332, 448-451; (d) R. Liu, X.
Liang, C. Dong and X. Hu, J. Am. Chem. Soc., 2004, 126, 4112-
4133; e) Y. Yao, Z. Wang, B.Wang, Org. Chem. Front., 2018, 5,
2501-2504.
(a) C. U. Kim, E. J. Corey, J. Am. Chem. Soc., 1972, 94, 7586–
7587; (b) C. U. Kim and E. J. Corey, Tetrahedron Lett., 1973,
12, 919-922; (c) P. L. Anelli, C. Biffi, S. Quici and F. Montanari,
J. Org. Chem., 1987, 52, 12, 2559-2562; (d) M. Kirihara, T.
Okada, Y. Sugiyama, M. Akiyoshi, T. Matsunaga and Y.
Kimura, Org. Process Res. Dev., 2017, 21, 1925-1937; (e) K.
Omura, D. Swern, Tetrahedron, 1978, 34, 1651-1660; (f) M.
H. A. Janssen, J. F. C. Castellana, H. Jackman, P. J. Dunnb and
R. A. Sheldon, Green Chem., 2011, 13, 905-912 (g) P. T. Lang,
A. M. Harned and J. E. Wissinger, J. Chem. Educ., 2011, 88,
652–656; (h) F. Minisci, F. Constantino, L. Liguori, H. R.
Bjorsvik, Org. Proc. Res. Dev., 2002, 6, 2, 197-200; (i) B. S.
Bal, W. E, Childers, H. W. Pinnick, Tetrahedron, 1981, 37,
2091-2096.
the desired imine product with the release of one molecule of
[10l-m]
H2O.
Kinetic studies indicate that the reaction is first
order with respect to both alcohols and amines which support
the formation of intermediate aldehyde and IM4 (see
Supporting Information, page S14-15).
3
Conclusion
In conclusion, using the sea abundant anion, Cl– as catalyst we
have for the first time developed a simple, sustainable and
efficient catalytic method for the oxidation of aromatic
alcohols to carboxylic acids or ketones and aromatic amines to
imines in water. The catalytic system involves NaCl (20 mol%),
NaOH (50 mol%) and aq. TBHP (4 equiv.) for alcohol oxidation.
Although, base is required for the oxidation of alcohols to
acids, oxidation of amines is possible even in the absence of a
base. A combination of radical and ionic mechanism is
responsible for alcohol oxidation. However, only ionic
mechanism seems to be operative in the case of amine
oxidation. Operational simplicity (as it is mostly
chromatography free), broad substrate scope, reusability of
side product (t-BuOH) and ease of scaling up are additional
features of this metal free and economical oxidation method.
Further applications of this catalytic system for oxidative
transformations are currently in progress in our laboratory and
we expect that our findings will inspire others to develop
sustainable sea-abundant anionic catalysts for organic
transformations.
4
5
6
Conflicts of interest
7
There are no conflicts of interest to declare.
Acknowledgements
The authors thank DST, India for financial assistance in the
form of research grant to A. J. E [DST EMR/2015/000285]. S.
H., M. D thank UGC, India, for research fellowship. We thank
DST-FIST and IIT D for funding the single crystal X-ray
diffraction and HRMS facilities at IIT Delhi.We thank Professor
A. R. Ramanan and Mrs Sujatha Ramanan for collecting sea
water used in this study from Kanyakumari, South India.
Thanks to CSMCRI, Bhavnagar, Gujarat, India for analysis of sea
water.
8
Notes and references
1
2
(a) J. V. Obligacion and P. J. Chirik, Nat. Rev. Chem., 2018, 2,
15–34; (b) P. J. Chirik and R. Morris, Acc. Chem. Res., 2015,
48, 2495−2495; (c) L. L. Schafer, P. Mountford and W. E.
Piers, Dalton Trans., 2015, 44, 12027–12028; (d) V. R. Ruiz, R.
Carlino, S. B. Lafollée, R. Gil, D. Prim, E. Schulzaand J.
Hannedouche, Dalton Trans., 2015, 44, 12029-12059.
(a) P. Gandeepan, T. Muller, D. Zell, G. Cera, S. Warratz and
L. Ackermann, DOI: 10.1021/acs.chemrev.8b00507; (b) B. Su,
Z. C. Cao and Z. J. Shi, Acc. Chem. Res., 2015, 48, 886-896; (c)
J. H. Docherty, J. Peng, A. P. Dominey and S. P. Thomas,
Nature Chemistry, 2017, 9, 595–600; (d) A. A. Toutov, W. -B.
9
(a) I. W. C. E. Arends, R. A. Sheldon, Modern Oxidation of
AlcoholsUsing Environmentally Benign Oxidants.In Modern
Oxidation Methods,2nd Ed.; J. –E. Bäckvall, Ed.; Wiley-VCH:
Weinheim, Germany, 2010, 147-185; (b) P. Hu, D. Milstein,
Conversion of Alcohols to Carboxylates Using Water and
Base with H2Liberation. In: .Topics in Organometallic
Chemistry. Springer, Berlin, Heidelberg, 2018; (c) M. –O.
Simon and C. –J. Li, Chem. Soc. Rev., 2012, 41, 1415-1427; (d)
T. Kitanosono, K. Masuda, P. Xu and S. Kobayashi, Chem. Rev.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 6 of 7
COMMUNICATION
Journal Name
2018, 118, 679−746; (e) C. J. Clarke, W. –C. Tu, O. Levers, A.
Bröhl and J. P. Hallett, Chem. Rev., 2018, 118, 747-800; (f) R.
A. Sheldon, Green Chem., 2017, 19, 18-43; (g) C. J. Li, Chem.
Rev., 1993, 93, 2023-2035; (h) R. N. Butler and A. G. Coyne,
Chem. Rev., 2010, 110, 10, 6302-6337; (i) B. H. Lipshutz,
Chem, 2018, 4, 2004-2007; (j) D. K. Romney, F. H. Arnold, B.
H. Lipshutz and C. –J. Li, J. Org. Chem., 2018, 83, 7319-7322.
10 (a) T. Zweifel, J. V. Naubron and H. Grützmacher, Angew.
Chem. Int. Ed., 2009, 48, 559-563; (b) E. Balaraman, E.
Khaskin, G. Leitus and D. Milstein, Nat. Chem., 2013, 5, 122-
125; (c) P. Hu, Y. Ben-David and D. Milstein, J. Am. Chem.
Soc., 2016, 138, 6143-6146; (d) A. Sarbajna, I. Dutta, P. Daw,
S. Dinda, S. M. W. Rahaman, A. Sarkar and J. K. Bera, ACS
Catal., 2017, 7, 2786-2790; (e) K. –I. Fujita, R. Tamura, Y.
Tanaka, M. Yoshida, M. Onoda, R. Yamaguchi, ACS Catal.,
2017, 7, 7226-7230; (f) R. Kawahara, K. –I. Fujita and R.
Yamaguchi, J. Am. Chem. Soc., 2012, 134, 3643-3646; (g) O.
Verho, M. D. V. Dilenstam, M. D. Kärkäs, E. V. Johnston, T.
Åkermark, J. –E. Bäckvall and B. Åkermark, Chem. Eur. J.,
2012, 18, 16947-16954; (h) M. Largeron, Org. Biomol.
Chem.,2017, 15, 4722-4730; (i) D. V. Jwale, E. Gravel, E.
Villemin, N. Shah, V. Geertsen, I. N. N. Namboothiri and E.
Doris, Chem.Commun., 2014, 50, 15251-15254; (j) H.
Yuan, W. J. Yoo, H. Miyamura and S. Kobayashi, J. Am. Chem.
Soc., 2012, 134, 13970-13973; (k) Z, Hu, F. M. Kerton, Org.
Biomol. Chem., 2012, 10, 1618-1624; (l) S. Hazra, P. Pilania,
M. Deb, A. K. Kushawaha and A. J. Elias, Chem. Eur. J., 2018,
24, 15766-15771; (m) M. Deb, S. Hazra, P. Dolui and A. J.
Elias, ACS Sustainable Chem. Eng., 2019, 7, 479−486. (n) S.
Hazra, M. Deb, J. Singh and A. J. Elias, Organometallics, 2017,
36, 1784-1794.
View Article Online
DOI: 10.1039/C9GC00497A
11 (a) X. Jiang, J. Zhang and S. Ma, J. Am. Chem. Soc., 2016, 138,
8344-8347; (b) P. D. Giorgi, N. Elizarov and S. Antoniotii,
ChemCatChem., 2017, 9, 1830-1836; (c) B. N. Zope, D. D.
Hibbitts, M. Neurock and R. J. Davis, Science, 2010, 330, 74-
77; (d) M. S. Ahmed, D. S. Mannel, T. W. Root and S. S. Stahl,
Org. Process Res. Dev., 2017, 21, 1388-1393; (e) Z. Naderi, M.
Khorasani, H. M. Mirzaei, H. Vali and B. Karimi,
ChemCatChem, 2016, 8, 906-910; (f) K. –J. Liu, S. Jiang, L. –H.
Lu, L. –L. Tang, S. –S. Tang, H. –S. Tang, Z. Tang, X. Xu and W.
–M. He, Green Chem., 2018, 20, 3038-3043; (g) J. Liu, S. Li, B,
Chen, J. Cheng, J. Kuang, Y. Liu, B. Wan, Y. Wang, J. Ye, Q. Yu,
W. Yuan, S. Yu and S. Ma, Adv. Synth. Catal., 2011, 353,
1005-1017.
12 G. Dilauro, F. A. Quivelli, P. Vitale, F. M. Perna and V.
Capriati, Angew. Chem. Int. Ed., 2019, 58, 1799-1802.
13 (a) J. Sanchez and T. N. Myers, Peroxides and Peroxide
Compounds, Organic Peroxides, Kirk-Othmer Encyclopedia of
Chemical Technology, Wiley-VCH Verlag GmbH & Co, 2000;
(b) https://en.wikipedia.org/wiki/Tert-Butyl_hydroperoxide.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C9GC00497A
192x111mm (96 x 96 DPI)