A convenient room temperature ipso-nitration of arylboronic acid catalysed by molecular iodine using zirconium oxynitrate as nitrating species: An experimental and theoretical investigation

Article abstract of DOI:10.1002/aoc.4951

A simple and convenient protocol has been developed for ipso-nitration of arylboronic acid catalysed by molecular iodine at room temperature, using zirconium oxynitrate as the nitrating species. The protocol is applicable to electronically diverse aryl- and heteroarylboronic acid moieties under mild reaction conditions with good to excellent isolated yields. Furthermore, a theoretical investigation has been performed for the same reaction, and reaction profiles are modelled using modern density functional theory (DFT). DFT-based results support the experimentally observed results.

Full text of DOI:10.1002/aoc.4951

Received: 6 October 2018
DOI: 10.1002/aoc.4951
Revised: 21 March 2019
Accepted: 22 March 2019
F U L L P A P E R
A convenient room temperature ipso‐nitration of
arylboronic acid catalysed by molecular iodine using
zirconium oxynitrate as nitrating species: An experimental
and theoretical investigation
Abhijit Mahanta1 | Nanda Kishor Gour1 | Plaban Jyoti Sarma1 | Raju Kumar Borah1 |
Prasanta Kumar Raul2 | Ramesh Chandra Deka1 | Ashim Jyoti Thakur1
| Utpal Bora1
1 Tezpur Central University, Tezpur
A simple and convenient protocol has been developed for ipso‐nitration of
arylboronic acid catalysed by molecular iodine at room temperature, using
zirconium oxynitrate as the nitrating species. The protocol is applicable to
electronically diverse aryl‐ and heteroarylboronic acid moieties under mild
reaction conditions with good to excellent isolated yields. Furthermore, a the-
oretical investigation has been performed for the same reaction, and reaction
profiles are modelled using modern density functional theory (DFT). DFT‐
based results support the experimentally observed results.
(Napaam), Assam 784028, India
2 Defence Research Laboratory, Tezpur,
Assam 784001, India
Correspondence
Ashim Jyoti Thakur and Utpal Bora,
Tezpur Central University, Tezpur
(Napaam), Assam, 784028, India.
Email: ashim@tezu.ernet.in;
utbora@yahoo.co.in
Funding information
Tezpur University; DST‐SERB, Grant/
Award Number: EMR/2016/005944
KEYWORDS
iodine, ipso‐nitration, zirconium oxynitrate
1 | INTRODUCTION
strong acid and secondly to the requirement of high tem-
perature. Another common reagent for nitration of
In the challenging domain of synthetic organic chemistry,
nitration of arenes has emerged as one of the most funda-
mental and important organic transformation reactions,
both for academic interest and industrial applications.
In real terms, over the decades, nitroarenes have shown
their potentialities by contributing to varieties of impor-
tant areas like pharmaceuticals, dyes and plastics.[1–4]
They have also been used as explosives and precursors
for azo dyes.[5] This indispensable significance in organic
synthesis may be attributed to their easy availability, ease
of transformation to other functional groups and the abil-
ity of nitroaryl moieties to impart tunable physical and
chemical properties to many structurally targeted organic
molecules. In general, the traditional method for synthe-
sis of nitroarenes involves electrophilic nitration of arenes
in the presence of excess amount of conc. sulfuric acid
and nitric acid under harsh reaction conditions which
are problematic, primarily due to the involvement of
arenes is dinitrogen pentoxide, which is a hazardous oxi-
dizer and an important reservoir[6,7] for NOx that are
responsible for ozone layer depletion and acid rain. Addi-
tionally, regioselectivity is a major issue in traditional
methods as the reaction is often associated with other oxi-
dation products and mixtures of isomers.[8] Therefore,
looking for some efficient alternative strategies eliminat-
ing the drawbacks of existing methodologies has signifi-
cance which has attracted considerable attention among
researchers and has become a long‐standing challenge
for synthetic organic chemists. In contemporary organic
synthesis, as far as nitration of arenes is concerned,
ipso‐nitration occupies a much superior position. In
2009, Fors and Buchwald reported[9] the nitration of aryl
chlorides, triflates and nonaflates to nitroaromatics
catalysed by Pd. It is a fascinating protocol, but use of
expensive ligand‐based Pd catalyst limits its practical
application. An efficient Cu‐catalysed protocol for the
Appl Organometal Chem. 2019;e4951.
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https://doi.org/10.1002/aoc.4951

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MAHANTA ET AL.
conversion of aryl iodides to nitrobenzene was reported
by Saito and co‐workers.[10] There are other reported
methodologies that include nickel nitrate‐catalysed nitra-
tion of phenolic compounds,[11] microwave‐assisted for-
mation of nitrorenens from phenolic compounds,[12] etc.
Aryl halides and phenolic compounds are known envi-
ronmental pollutants.[13] Additionally, by‐products of aryl
halides invite problems during isolation and purification
of desired products. In this context, nowadays, arylboronic
acids have emerged as interesting and versatile alternative
organic synthons for this type of transformation as they
offer some significant and preferable properties such as
non‐toxicity, heat and moisture resistance and easy
availability with varying substitutions.[14] Some
reagents/catalysts have been reported for the transforma-
with regard to green chemistry. Also, easily available
ZrO(NO3)2⋅XH2O is a safe and easy‐to‐handle nitrating
source.[24] In order to provide strong support to the exper-
imental work for the reaction under investigation, theo-
retical calculations were performed using density
functional theory (DFT). Here, based on these findings,
we present feasibility of the reaction and exploration of
the reaction pathway on potential energy surface (PES)
along with transition state (TS). Intrinsic reaction coordi-
nate (IRC) calculation was also performed to confirm the
smooth transition from reactant to product through the
respective TS.
To optimize our ipso‐nitration protocol, we planned to
investigate the reaction with different nitrate sources
such as cupric nitrate, ammonium nitrate, cobalt nitrate,
silver nitrate, zirconium oxynitrate, etc. To begin with, a
round‐bottomed flask was charged with 1 mmol of
phenylboronic acid as the model substrate and cupric
nitrate (2 mmol) as the nitrating agent under stirring
followed by heating to 80°C. Initially, we decided to per-
form the reaction with 15 mg of montmorillonite (K10)
clay as an acidic additive and it showed very little conver-
sion to nitroarenes along with formation of phenol as the
side product (Table 1, entry 1). Interestingly, the reaction
without K10 showed no conversion to nitroarene at all.
This particular result signified the importance of acidic
additive for targeted nitrobenzene product.
For the next assessment, we carried out the reaction
with diverse nitrate salts. When we replaced the cupric
nitrate salt by ammonium nitrate, cobalt nitrate, silver
nitrate and sodium nitrate, formation of phenol
discontinued but the yield of the nitroarene was found
to be moderate (Table 1, entries 2–5). However, we
observed slightly better results with zirconium oxynitrate
salt as nitrating source (Table 1, entry 6). Further, fixing
ZrO(NO3)2⋅XH2O (2 mmol), oxidants were altered with
the aim of achieving better conversion. Progress of
the reaction was checked with solid acids such as
p‐toluenesulfonic acid (p‐TSA), silica, alumina, etc. How-
ever, no noticeable improvement in result was observed
(Table 1, entries 7–9). Interestingly, use of o‐phosphoric
acid as an oxidant gave better conversion with
ZrO(NO3)2⋅XH2O as the nitrate source (Table 1, entry
10). However, acetic acid as an acid failed to afford a good
conversion of the desired product nitrobenzene. Interest-
ingly, the reaction catalysed by molecular iodine showed
the best conversion with trace amount of nitrosobenzene
(Table 1, entry 12) in 12 h at 80°C. Moreover, when using
other additives such as silica or K10 along with molecular
iodine, the reaction completed quickly although forma-
tion of nitrosobenzene was also observed. Then, we
proceeded to investigate the reaction with iodine
(20 mol%) as oxidant and tried with other nitrate sources
tion of arylboronic acids to nitroarenes, e.g. Bi(NO3)3/
K2S2O8,[15] TMS‐Cl/MNO3
(M = Ag, NH4), Cu2O/
[16]
NaNO2,[17] etc. Catalyst‐free conversion of arylboronic
acids to nitrobenzenes has also been carried out with bis-
muth nitrate[18] and iron nitrate[19] as nitrate sources.
Additionally, ipso‐nitration has been carried out with
tert‐butyl nitrite[20] as the nitrate source under catalyst‐
free conditions (Scheme 1).
Although some reports claim successful ipso‐nitration
of arylboronic acids, yet, in most cases, use of strong
acids,[21] prolonged reaction time (30–72 h), high temper-
ature,[22] etc., were necessary to maximize catalytic per-
formances. Moreover, many of them suffer limitations
regarding poor substrate scope and intolerance to hetero-
cyclic moieties. Therefore, a highly active catalytic system
is still desired for the said reaction protocol, which avoids
the drawbacks like using high temperature, strong acid,
etc., because these drawbacks go against the ‘green sus-
tainable chemistry’ principles.
Taking into consideration the points mentioned above,
herein, we report a facile and practical method for ipso‐
nitration of arylboronic acids in the presence of molecu-
lar iodine (I2) as catalyst, zirconium nitrate as nitrating
source and toluene as solvent. In recent times, there has
been an increasing interest in molecular iodine‐catalysed
organic transformations owing to its numerous advan-
tages such as it being a powerful, inexpensive, non‐toxic
and readily available catalyst.[23] This has also relevance
SCHEME 1 Previous works on ipso‐nitration reaction

MAHANTA ET AL.
3 of 10
TABLE 1 Optimization of reaction conditionsa for different additives, nitrate salt, amount of catalyst and temperature
Time
(h)
Entry
Nitrate salt
Additive
Yield (%)b
1
Cupric nitrate
K10 (15 mg)
K10 (15 mg)
K10 (15 mg)
K10 (15 mg)
K10 (15 mg)
K10 (15 mg)
p‐TSA (15 mg)
Silica (15 mg)
Alumina (15 mg)
H3PO4 (2 ml)
CH3COOH (2 ml)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (15 mol%)
I2 (10 mol%)
I2 (5 mol%)
24
24
24
24
24
24
24
24
24
24
24
12
12
12
12
12
12
12
12
24
18
18
18
12
20
25
40
8
2
Ammonium nitrate
Cobalt nitrate
3
4
Silver nitrate
5
Sodium nitrate
13
6
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Cupric nitrate
55 + 5% nitroso
7
42
8
34 + 15% nitroso
9
45
10
11
12
13
14
15
16
17
18
19
20
21c
22c,d
23c,e
24c,d,f
84
23
89 + 5% nitroso
45
25
20
28
30
89
89
67
89
89
65
92
Cobalt nitrate
Ammonium nitrate
Silver nitrate
Sodium nitrite
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
Zirconium oxynitrate
I2 (10 mol%)
I2 (10 mol%)
I2 (10 mol%)
I2 (10 mol%)
aReaction conditions: phenylboronic acid (1 mmol), nitrate salt (2 mmol), toluene (3 ml).
bIsolated yield.
cRoom temperature ca 34°C in air, unless otherwise noted.
d1.5 mmol of the nitrate salt was used.
e1 mmol of the nitrate salt was used.
fUnder nitrogen atmosphere.
(Table 1, entries 13–17). Again, we found zirconium
nitrate as the most suitable nitrating agent for the ipso‐
nitration protocol.
the catalyst in 12 h. However, the reaction with 5 mol%
of the catalyst did not show completion even after 24 h.
Interestingly, when the reaction was carried out at room
temperature using 10 mol% of the catalyst, to our delight,
the reaction completed with the same yield of conversion
in 18 h (Table 1, entry 21). Later, by varying the amount
of the nitrate salt, we found the best result with 1.5 mmol
of the nitrate salt (Table 1, entry 22), and further reducing
the amount nitrate salt to 1 mmol afforded lower yield of
the product (Table 1, entry 23). To investigate the effect of
air in the reaction, we performed a reaction under
Several test reactions were carried out using different
amounts of I2 to optimize the amount of catalyst for max-
imum yield of product. It has been observed that with
20 mol% of the catalyst (molecular iodine), the reaction
completed in 12 h (Table 1, entry 12). Then, the reaction
was carried out with 15, 10 and 5 mol% (Table 1, entries
18–20) of catalyst under the same reaction conditions.
Comparable yield was obtained with 15 and 10 mol% of

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MAHANTA ET AL.
TABLE 2 Molecular iodine‐catalysed synthesis of nitrobenzene
donating groups were also found to give corresponding
nitrobenzene in excellent yields. Heteroarylboronic acids
provided moderate results (Table 2, entries 12 and 13).
Interestingly, no significant effects were observed for
sterically demanding arylboronic acid moieties (Table 2,
entries 5, 10, 12, 13, 15 and 16) as well as electron‐
donating and electron‐withdrawing substrates.
from arylboronic acidsa
Entry
R
Time (h)
Yield (%)b,c
1
H
12
18
12
20
18
18
16
12
12
20
16
8
89
84
85
79
85
87
85
89
86
78
81
83
80
86
86
84
88
It has been reported that the ipso‐nitration of
arylboronic acids usually progresses through a free radical
pathway.[19] So, to investigate the reaction mechanism, at
first we performed a radical trapping experiment by using
stoichiometric amount of radical scavenger 2,2,6,6‐
tetramethylpiperidine‐N‐oxide (TEMPO). We added
TEMPO to the reaction mixture under the same conditions
but the reaction was found to progress even after addition
of the same; this result ruled out the possibility of a radical
mechanism for the current reaction protocol.
Therefore, we have suggested a plausible mechanistic
pathway based on the reported non‐radical pathway,[16]
as shown in Figure 1. It is believed that, initially, iodine
(I2) molecule reacts with nitrate salt [ZrO(NO3)2H2O] to
form IONO2 and ZrO(NO3)(H2O)I species. Subsequently
the oxygen atom of IONO2 species reacts at electron‐
deficient boron atom of arylboronic acid via the lone pair
of electrons and forms an intermediate (A) which
rearranges to form the desired nitrobenzene product and
IOB(OH)2 species. It is also important to note that the by‐
2
4‐Bromo
3
4‐Formyl
3‐Formyl
2,4‐Dichloro
3‐Chloro
4
5
6
7
4‐Hydroxy
4‐Amino
8
9
4‐Methoxy
2‐Methyl
10
11
12
13
14
15
16
17
4‐Methyl
2‐Thiophenyl
2‐Methoxy‐6‐pyridyl
4‐Fluoro
11
14
17
16
14
2,4‐Difluoro
2‐Chloro
4‐Chloro
products of step 1 [ZrO(NO3)(H2O)I] and step
2
aReaction conditions: phenylboronic acid (1 mmol), nitrate salt (1.5 mmol),
toluene (3 ml).
bIsolated yield,
[IOB(OH)2] combine with each other to form ZrO(NO3)
(OH) complex and H3BO3 molecule and regeneration of
I2 as shown in step 3.
cUnder nitrogen atmosphere.
To visualize the reaction mechanism and thermo-
chemistry of the main step (step 2) along with the other
two steps as given in Figure 1, a theoretical investigation
was performed using the DFT approach. Optimized struc-
tures of all species (including intermediates and TSs)
involved in the title reaction (steps 1, 2 and 3) were
obtained with B3LYP functional along with 6‐311G+(d)/
LanL2DZ basis sets as shown in Figure 2. In the first step,
when I2 reacts with [ZrO(NO3)2(H2O)], a reaction com-
plex (RC1) and TS (TS1) are formed before the formation
of products. In RC1, we observed that the bond distances
between Zr atom and two O atoms of [ZrO(NO3)2(H2O)]
are found to be 2.397 Å and 2.284 Å. These observed bond
distances are longer than the Zr–O bond lengths (2.299 Å
and 2.305 Å) in the parent [ZrO(NO3)2(H2O)] complex. In
addition, the distances of two I atoms of I2 with Zr and O
atoms of the complex are found to be 3.406 Å and
2.715 Å, while distance between I2 is 3.397 Å. In TS1,
Zr–O distances further increase from RC1 and became
2.414 Å and 2.379 Å, respectively. It is also found that
bond distance of newly formed Zr–I and O–I bonds
increased in TS1, which indicates the breaking of Zr–O
nitrogen atmosphere keeping all other reaction parame-
ters the same as in entry 24 of Table 1. Interestingly, we
observed a better result with exclusive formation of nitro-
benzene. Formation of by‐product nitrosobenzene was
completely eliminated under nitrogen atmosphere. Addi-
tionally, the reaction completed within a short time inter-
val in comparison to air atmosphere. To study the effect
of solvents in our system, the reaction was investigated
with various polar, non‐polar, protic and aprotic solvents.
Among the aprotic solvents such as toluene, xylene,
dichloromethane (DCM) and chloroform, except toluene
and xylene, the others failed to show efficiency as good
solvents. The reaction did not proceed smoothly in
dimethylsulfoxide, isopropanol, methanol and water and
showed poor conversion. Between toluene and xylene,
we consider toluene as the best solvent.
With the optimized reaction conditions (Table 1, entry
24), further study of the generality of the ipso‐nitration
protocol was extended to a variety of substituted
arylboronic acids (Table 2, entries 1–17). Phenylboronic
acids having electron‐withdrawing as well as electron‐

MAHANTA ET AL.
5 of 10
FIGURE 1 Reaction steps for the
formation of nitrobenzene and I2
regeneration
and I2 bonds and formation of IONO2and [ZrO(NO3)
(H2O)I] species via product complex (PC1). In the next
steps, IONO2 reacts with arylboronic acid leading to the
formation of RC2, then proceeding via TS2 to give the
final product via PC2. In RC2, N and O atoms of IONO2
are making bonds with the C and B atoms of arylboronic
acid at distances of 2.978 Å and 2.267 Å, respectively. In
TS2, the respective bond distances are decreased to
2.247 Å and 1.614 Å and reveal the formation of C–N
and O–B bonds. Moreover, it was observed that the N–
O distance in IONO2 increases from 1.552 Å to 1.963 Å
with respect to RC2. During the formation of products
[nitrobenzene + IOB(OH)2], C–B and N–O bonds break
completely and C–N and O–B bonds are formed. In the
last step, the by‐products of previous steps react together
to give RC3 which further regenerates I2 via TS3 along
with [ZrO(NO3)(OH)] and H3BO3. In RC3, O–H and Zr–
I distances are increased to 1.069 and 3.296 Å with
respect to initial bond parameters of [ZrO(NO3)(H2O)I]
and also O–I distance is increased to 2.216 Å from the ini-
tial IOB(OH)2 species. In TS3, the bond distances of O–H
and Zr–I increase to 1.350 Å and 3.351 Å compared to the
distances in RC3. The O–I distance increases to 2.299 Å in
TS3, while distance between I2 decreased to 3.035 Å com-
pared to that in RC3. Finally, O–H and Zr–I bonds break
in [ZrO(NO3)(H2O)I] and O–I bond breaks in IOB(OH)2
and forms O–H bond in IOB(OH)2 and I2 is completely
regenerated.
Vibrational frequency calculations were further per-
formed for all of the optimized structures involved in
the various steps at same level of theory to understand
the various modes of vibrations (real or imaginary) and
thermochemistry. We observed from this calculation that
all species are found to have real positive vibrational fre-
quencies (corresponding to stable minima) except TSs
which have negative frequencies at 77i cm−1 (TS1),
256i cm−1 (TS2) and 71i cm−1 (TS3). Visualization of
the imaginary frequencies revealed a qualitative confir-
mation of the existence of TSs connecting reactant‐ and
product‐like structures. IRC calculations were also per-
formed for TS1, TS2 and TS3 at the same level of theory
to investigate the connectivity of each TS with reactant‐
and product‐like structures. IRC results show that each
TS smoothly connects the reactant‐ and product‐like
structures. An IRC plot of TS2 for the main reaction is
shown in Figure 3.
To understand the feasibility of the reaction path, stan-
dard reaction enthalpy (ΔrH0) and Gibbs free energy
(ΔrG0) for the title reaction along with two other reac-
tions were calculated (using the data provided in the
supporting information, Table S18). The values of ΔrH0
and ΔrG0 for step 1 are found to be 26.77 and
35.75 kcal mol−1, respectively, indicating that this step
is endothermic at 298 K. For step 2, these values are
obtained as −67.86 and −67.84 kcal mol−1, respectively,
which indicate the feasibility of the reaction. These values

6 of 10
MAHANTA ET AL.
FIGURE 2 Optimized structures of species including intermediates and transition states in all steps
are found to be −25.10 and −36.64 kcal mol−1 for step 3
in which I2 is regenerated. This indicates that the reaction
is exothermic and feasible at room temperature and thus
I2 is easily regenerated.
to carry out the next catalytic cycle. The involvement of
each species in the mechanism is shown in Figure 5.
In conclusion, we have developed a mild, facile and
efficient methodology for ipso‐nitration of arylboronic
acids catalysed by molecular iodine (10 mol%) at
room temperature with moderate to excellent yields.
The methodology is applicable to both aryl‐ and
heteroarylboronic acids within a short reaction time.
The new protocol is superior to the existing methodolo-
gies as it uses mild and safe nitrating source avoiding
stronger acids. The most important factor is that the
reaction occurs at room temperature and so is an
energy‐saving process. The reaction has added advan-
tages such as it does not require any base or ligand. We
have also analysed the reaction mechanism theoretically
using modern DFT. Our theoretical results show that the
Relative energies (including ZPE) for each of the spe-
cies were determined (Table S18, supporting information)
with respect to the reactants, setting it arbitrarily at zero,
and the results are recorded in Table 3. Potential energy
diagrams (Figure 4) of all steps were constructed with
the results obtained at the DFT (B3LYP) level. The results
show that the barrier height of step 1 is 3.57 kcal mol−1
and in step 2 the barrier height is 16.99 kcal mol−1
.
Although the barrier height of TS2 is slightly higher,
which is main reaction, the reaction is highly exothermic.
In step 3, the barrier height is very small and equal to
1.41 kcal mol−1 which indicates that I2 regenerates easily

MAHANTA ET AL.
7 of 10
and Zr atoms, we employed Los Alamos National Labora-
tory 2 double zeta (LanL2DZ) basis set with effective core
potential[28] for both heavy atoms present. In order to
determine the nature of stationary points on the PES,
vibrational frequency calculation was made using the
same level of theory at which the optimization was made.
All the electronic calculations were performed using the
Gaussian 09 program package.[29] The stationary points
were identified to correspond to stable minima on the
respective PES by ascertaining that all the harmonic
vibrational frequencies were real and positive. The TSs
in the reaction were obtained using synchronous
transition‐guided quasi‐Newton method[30,31] and the
first‐order saddle point was characterized by the presence
of only one imaginary frequency (NIMAG = 1). IRC cal-
culations were also performed in order to ascertain that
the transition of reactant to product via corresponding
TS was smooth. The minimum energy path was obtained
by IRC calculation.[32]
FIGURE 3 IRC plot for TS2 at B3LYP/6‐311G+(d)/LanL2DZ
level of theory
3 | EXPERIMENTAL
3.1 | General information
reaction is thermodynamically favourable which is
reflected in the PES diagram (Figure 4).
1H NMR and 13C NMR spectra of the products were
recorded with a JNM ECS 400 MHz NMR spectrophotom-
eter (JEOL) using tetramethylsilane as the internal
standard. Chemical shift values are expressed in ppm.
Coupling constants are expressed in hertz. Reactions
were monitored by TLC using aluminium sheets with sil-
ica gel 60F254 (Merck). UV light and iodine vapours were
used as visualizer. Chemicals were obtained from com-
mercial sources.
2 | COMPUTATIONAL DETAILS
The geometries of all the species involved in steps 1, 2
and 3 along with intermediates (RCs and PCs) and TSs
were optimized with the B3LYP functional[25,26] of DFT.
During geometry optimization, the 6‐311G+(d) basis
set[27] was used for all elements except heavy atoms
(I and Zr). Considering the strong relativistic effect of I
3.2 | General experimental procedure for
ipso‐nitration of arylboronic acid
TABLE 3 Relative energies (kcal mol−1) of species involved in
the reaction calculated with DFT (B3LYP) and levels of theory
A 50 ml two‐necked round‐bottomed flask was charged
with arylboronic acid (1 mmol), ZrO(NO3)2⋅xH2O
(1.5 mmol) and iodine (10 mol%) and the reaction mix-
ture was stirred at room temperature in toluene (4 ml)
under nitrogen atmosphere. After completion of the reac-
tion (TLC), the reaction mixture was filtered with
Whatman filter paper and the residue was washed with
ethyl acetate followed by DCM (3 × 15 ml) and diluted
with water (10 ml). The DCM extract was washed with
sodium thiosulfate solution (10 ml). The separated
organic layer was dried over anhydrous sodium sulfate,
filtered and concentrated under reduced pressure. The
crude material so obtained was purified by column chro-
matography on silica gel (ethyl acetate–hexane eluent).
Reaction step Species
Relative energy
Step 1
Step 2
Step 3
Zr(O)(H2O)(NO3)2 + I2
RC1
TS1
PC1
0.00
28.80
32.37
26.33
29.75
Zr(O)(NO3)(H2O)I + IONO2
C6H5B(OH)2 + IONO2
RC2
TS2
PC2
0.00
73.17
90.16
41.16
−67.79
C6H5NO2 + IOB(OH)2
ZrO(NO3)(H2O)I + IOB(OH)2
0.00
−21.92
−20.50
RC3
TS3
ZrO(NO3)OH + H3BO3 + I2 −25.62
1
All the compounds were characterized using H NMR

8 of 10
MAHANTA ET AL.
FIGURE 4 Potential energy diagrams of (a) step 1 (black), (b) step 2 (blue) and (c) step 3 (pink) at B3LYP//6‐311G+(d)/LanL2DZ level of
theory
and 13C NMR spectroscopy and the data finally compared
with those of authentic compounds.
8.10 (d, J = 8.4 Hz, 2H); 13C NMR (100 MHz, CDCl3, δ,
ppm): 190.5, 151.1, 140.1, 130.6, 124.3.
3‐Formylbiphenyl (entry 4, Table 2): Brown solid
(119 mg, 79%); m.p. 55–60°C; 1H NMR (400 MHz, CDCl3,
δ, ppm): 10.14 (s, 1H), 8.73–8.72 (m, 1H), 8.53–8.50 (m,
1H), 8.25 (d, J = 8 Hz, 1H), 7.81–7.77 (m, 1H); 13C
NMR (100 MHz, CDCl3, δ, ppm): 189.9, 148.8, 137.4,
134.8, 130.5, 128.7, 124.5.
2,4‐Dichloronitrobenzene (entry 5, Table 2): Yellow
liquid (163 mg, 85%); 1H NMR (400 MHz, CDCl3, δ,
ppm): 7.83 (s, 1H), 7.48–7.47 (m, 2H); 13C NMR
(100 MHz, CDCl3, δ, ppm): 156.6, 138.7, 131.1, 130.9,
129.7, 128.8, 128.2, 127.5, 126.9, 121.0, 111.4, 55.7.
3‐Chloronitrobenzene (entry 6, Table 2): White solid
(135 mg, 87%); m.p. 43–50°C; 1H NMR (400 MHz,
CDCl3, δ, ppm): 8.22–8.21 (m, 1H), 8.15–8.10 (m, 1H),
6.663–6.661 (m, 1H), 7.51–7.47 (m, 1H); 13C NMR
(100 MHz, CDCl3, δ, ppm): 148.8, 135.5, 134.8, 128.3,
130.4, 123.9, 121.7.
3.3 | Characterization data of compounds
Nitrobenzene (entry 1, Table 2): Yellow liquid (109 mg,
89%); 1H NMR (400 MHz, CDCl3, δ, ppm): 8.21 (d,
J = 8.4 Hz, 2H), 7.70–7.68 (m, 1H), 7.54 (d, J = 8 Hz,
2H); 13C NMR (100 MHz, CDCl3, δ, ppm): 148.2, 134.7,
129.4, 123.3.
4‐Bromonitrobenzene (entry 2, Table 2): White solid
(168 mg, 84%); m.p. 120–126°C; 1H NMR (400 MHz,
CDCl3, δ, ppm): 8.08 (d, J = 7.6 Hz, 2H), 7.67 (d,
J = 7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3, δ, ppm):
147.0, 132.7, 132.5, 130.0, 125.0.
4‐Formylnitrobenzene (entry 3, Table 2): White solid
(128 mg, 85%); m.p. 102–106°C; 1H NMR (400 MHz,
CDCl3, δ, ppm): 10.18 (s, 1H), 8.40 (d, J = 6.8 Hz, 2H),

MAHANTA ET AL.
9 of 10
FIGURE 5 Schematic diagram of the
reaction mechanism
4‐Hydroxynitrobenzene (entry 7, Table 2): White solid
(119 mg, 85%); m.p. 270–275°C; 1H NMR (400 MHz,
CDCl3, δ, ppm): 8.18 (d, J = 9.2 Hz, 2H), 6.94 (d,
J = 8 Hz, 2H), 6.66 (1H, br s); 13C NMR (100 MHz,
CDCl3, δ, ppm): 161.7, 141.5, 126.4, 115.8.
4‐Aminonitrobenzene (entry 8, Table 2): Yellow solid
(237 mg, 89%); m.p. 330–335 C; 1H NMR (400 MHz,
acetone‐d6, δ, ppm): 7.95 (d, J = 6.8 Hz, 2H), 6.70 (d,
J = 7.2 Hz, 2H), 6.03 (br s, 1H); 13C NMR (100 MHz,
CDCl3, δ, ppm): 155.2, 137.3, 126.1, 112.7.
4‐Methoxynitrobenzene (entry 9, Table 2): White solid
(242 mg, 86%); m.p. 50–53°C; 1H NMR (400 MHz, CDCl3,
δ, ppm): 8.22–8.19 (d, J = 9.2 Hz, 2H), 6.96 (d, J = 7.2 Hz,
2H), 3.91 (s, 3H); 13C NMR (100 MHz, CDCl3, δ, ppm):
164.6, 141.5, 126.0, 114.0, 56.0.
2‐Methylnitrobenzene (entry 10, Table 2): Yellow
liquid (107 mg, 78%); 1H NMR (400 MHz, CDCl3, δ,
ppm): 7.13–7.09 (m, 1H), 6.75–6.73 (m, 1H), 6.65–6.62
(m, 2H), 2.29 (s, 3H); 13C NMR (100 MHz, CDCl3, δ,
ppm): 155.5, 139.9, 129.5, 121.6, 116.1, 112.3, 21.4.
4‐Methylnitrobenzene (entry 11, Table 2): White solid
(110 mg, 81%); m.p. 50–55°C; 1H NMR (400 MHz, CDCl3,
δ, ppm): 8.11 (d, J = 8.8 Hz, 2H), 7.33–7.27 (m, 2H), 2.46
(s, 3H); 13C NMR (100 MHz, CDCl3, δ, ppm): 146.1, 129.9,
123.5, 21.7.
CDCl3, δ, ppm): 7.93–7.92 (m, 1H), 7.56–7.55 (m, 1H),
7.40–7.39 (m, 1H); 13C NMR (100 MHz, CDCl3, δ, ppm):
132.6, 128.6, 127.5, 127.0, 126.9.
3‐Methoxy‐2‐nitropyridine (entry 13, Table 2): White
solid (123 mg, 80%); m.p. 75–80°C; 1H NMR
(400 MHz, CDCl3, δ, ppm): 8.41–8.40 (m, 1H), 8.29–
8.28 (m, 1H), 7.07–7.04 (m, 1H), 4.12 (s, 3H); 13C
NMR (100 MHz, CDCl3, δ, ppm): 156.6, 151.8, 135.1,
134.0, 116.5, 54.8.
4‐Fluoronitrobenzene (entry 14, Table 2): Yellow liq-
1
uid (121 mg, 86%); H NMR (400 MHz, CDCl3, δ, ppm):
8.28 (d, J = 8 Hz, 2H), 7.24 (d, J = 8 Hz, 2H), 7.39–7.36
(m, 2H); 13C NMR (100 MHz, CDCl3, δ, ppm): 167.6,
165.0, 144.4, 126.4, 126.3, 116.5, 116.3.
2,4‐Diflouronitrobenzene (entry 15, Table 2): Yellow
solid (136.74 mg, 86%); m.p. 12–15°C; 1H NMR
(400 MHz, CDCl3, δ, ppm): 8.19–8.17 (m, 1H), 7.09–7.05
(m, 2H); 13C NMR (100 MHz, CDCl3, δ, ppm): 167.1,
164.4, 134.1, 128.3, 128.27, 112.2, 106.6.
2‐Chloronitrobenzene (entry 16, Table 2): Yellow solid
(131.88 mg, 84%); m.p. 30–33°C; 1H NMR (400 MHz,
CDCl3, δ, ppm): 7.87–7.85 (m, 1H), 7.56–7.53 (m, 2H),
7.45–7.40 (m, 2H); 13C NMR (100 MHz, CDCl3, δ, ppm):
148.1, 133.2, 131.9, 127.4, 125.6.
4‐Chloronitrobenzene (entry 17, Table 2): Yellow solid
(138 mg, 88%); m.p. 80–85°C; 1H NMR (400 MHz, CDCl3,
δ, ppm): 8.79 (d, J = 8.4 Hz, 2H), 7.52 (d, J = 9.2 Hz, 2H);
2‐Thiophenylnitrobenzene (entry 12, Table 2): White
1
solid (107 mg, 83%); m.p. 40–45°C; H NMR (400 MHz,

10 of 10
MAHANTA ET AL.
13C NMR (100 MHz, CDCl3, δ, ppm): 146.5, 141.4, 129.6,
[13] J. F. Rustling, Acc. Chem. Res. 1991, 24, 75.
[14] M. Mandal, U. Bora, Green Chem. 2012, 14, 1873.
125.0.
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NOTES
[16] G. K. S. Prakash, C. Panja, T. Mathew, V. Surampudi, N. A.
The authors declare no competing financial interest.
Petasis, G. A. Olah, Org. Lett. 2004, 6, 2205.
[17] H. Yang, Y. Li, M. Jiang, J. Wang, H. Fu, Chem. Eur. J. 2011, 17,
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ACKNOWLEDGMENTS
[18] R. R. Yadav, R. A. Vishwakarma, S. B. Bharate, Tetrahedron
Lett. 2012, 53, 5958.
The authors acknowledge the DST‐SERB, New Delhi for
financial support for this work (SERB/DST no.
EMR/2016/005944). The authors are grateful to Tezpur
University for the infrastructural facilities and institu-
tional fellowship to A.M. One of the authors (N.K.G.) is
grateful to UGC for DS‐Kothari postdoctoral fellowship.
[19] M. Jiang, H. Yang, Y. Li, Z. Jia, H. Fu, RSC Adv. 2013, 3, 25602.
[20] X. F. Wu, J. Schranck, H. Newmann, M. Beller, Chem.
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[22] Y. K. Liu, S. J. Lou, D. Q. Xu, Z. Y. Xu, Chem. Eur. J. 2012, 16,
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ORCID
Ashim Jyoti Thakur
6725
Utpal Bora https://orcid.org/0000-0002-7403-0152
https://orcid.org/0000-0003-0923-
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