Isoquinolinium-N-sulfonic acid thiocyanate/H2O2 as efficient reagent for thiocyanation of N-bearing (hetero)aromatic compounds

Article abstract of DOI:10.1080/17415993.2021.1929230

In the present study, isoquinoline sulfonic acid thiocyanate (isoquinoline-SO₃H)SCN and isoquinoline sulfonic acid chloride (isoquinoline-SO₃H)Cl as a novel and heterogeneous catalyst were designed and synthesized by a simple and ine

Full text of DOI:10.1080/17415993.2021.1929230

Journal of Sulfur Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gsrp20
Isoquinolinium-N-sulfonic acid thiocyanate/H2O2
as efficient reagent for thiocyanation of N-bearing
(hetero)aromatic compounds
Sobhan Rezayati, Fatemeh Kalantari, Ali Ramazani & Elham Ezzatzadeh
To cite this article: Sobhan Rezayati, Fatemeh Kalantari, Ali Ramazani & Elham Ezzatzadeh
(2021) Isoquinolinium-N-sulfonic acid thiocyanate/H2O2 as efficient reagent for thiocyanation
of N-bearing (hetero)aromatic compounds, Journal of Sulfur Chemistry, 42:5, 575-590, DOI:
10.1080/17415993.2021.1929230
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JOURNAL OF SULFUR CHEMISTRY
2021, VOL. 42, NO. 5, 575–590
https://doi.org/10.1080/17415993.2021.1929230
Isoquinolinium-N-sulfonic acid thiocyanate/H2O2 as efficient
reagent for thiocyanation of N-bearing (hetero)aromatic
compounds
c
Sobhan Rezayati a, Fatemeh Kalantaria, Ali Ramazani a,b and Elham Ezzatzadeh
aDepartment of Chemistry, Faculty of Science, University of Zanjan, Zanjan 45371-38791, Iran; bDepartment
of Biotechnology, Research Institute of Modern Biological Techniques (RIMBT), University of Zanjan, Zanjan,
Iran; cDepartment of Chemistry, Ardabil Branch, Islamic Azad University, Ardabil, Iran
ABSTRACT
ARTICLE HISTORY
Received 20 March 2021
Accepted 7 May 2021
In the present study, isoquinoline sulfonic acid thiocyanate (isoqui
noline-SO3H)SCN and isoquinoline sulfonic acid chloride (isoquino
line-SO3H)Cl as a novel and heterogeneous catalyst were designed
and synthesized by a simple and inexpensive procedure. The
prepared heterogeneous catalyst was characterized by FT-IR, 1H
NMR, and 13C NMR techniques. Then, the catalytic activity of
(isoquinoline-SO3H)SCN and (isoquinoline-SO3H)Cl were success-
fully investigated for the synthesis of aryl and heteroaryl thio-
cyanates derivatives through a one-pot reaction. Moreover, the
use of (isoquinoline-SO3H)SCN provides a quite simple and more
convenient procedure, due to it has both acidic group and thio-
cyanation agent in reaction. The present procedure offers advan-
tages such as the usage of a commercially available materials,
cheap and chemically stabile reagents, short reaction time, excel-
lent yield, ease of separation by simple filtration, and simple reaction
work-up.
KEYWORDS
(isoquinoline-SO3H)SCN;
(isoquinoline-SO3H)Cl; solid
acid; H2O2; heterogeneous
catalyst
CONTACT Ali Ramazani
aliramazani@znu.ac.ir; aliramazani@gmail.com
Department of Chemistry, Faculty of
Science, University of Zanjan, Zanjan 45371-38791, Iran; Department of Biotechnology, Research Institute of Modern
Biological Techniques (RIMBT), University of Zanjan, Zanjan 45371-38791, Iran
Supplemental data for this article can be accessed here. https://doi.org/10.1080/17415993.2021.1929230
© 2021 Informa UK Limited, trading as Taylor & Francis Group

576
S. REZAYATI ET AL.
1. Introduction
The development of the catalysts especially heterogeneous catalyst has found a significant
place in modern organic synthesis. It is also a new way to meet the challenges of energy
and sustainability. The application of solid acids in the realm of organic synthesis is vital
because they offer many advantages including simplified recovery, ease of handling, incor-
poration in continuous reactors and microreactors, enhanced selectivity and reactivity, and
easy product isolation. Also, solid acids have no corrosion or disposal of effluent problems,
so they can lead to environmentally benign chemical method for industry and academia
[1–3]. Recently, 103 solid acids catalysts are used in more than 100 industrial processes [4].
Nowadays, the electrophilic thiocyanation of N-bearing (hetero)aromatic compounds is
one of the most important research activities for chemists and pharmacists both in the lab-
oratory and industry. Thiocyanates are significant because of their applications in various
areas of pharmaceutical importance [5]. For example, Pezzalla and their colleague synthe-
sized some of 3-indolylthiols derivatives. The reaction was carried out via condensation of
3-thiocyanatoin-doles using SmI2 reduction and subsequently acetylation (Scheme 1) [6].
3-indolylthiols were used as anti-angina, HIV-treating [7], and anti-allergy agents [8].
Moreover, this method is included in a direct method for the formation of C–S bonds,
which is a very useful reaction in organic synthesis [9]. Thiocyanate compounds have
an essential role in various areas of organosulfur chemistry which can be readily trans-
formed into other functional groups such as thionitrile [10], aryl nitrile [11], thiocarbamate
[12], sulfide [13], thiophenols [14], allyl sulfides [15], 5-sulfenyl tetrazoles [16], alkyl
trifluoromethyl thioethers [17], disulfides [18], nitriles [19] and S-argio carbamothioate
[20] (Scheme 2). Additionally, the products of thiocyanates and thiocyanation have been

JOURNAL OF SULFUR CHEMISTRY
577
Scheme 1. Synthesis of 3-indolylthiols.
Scheme 2. Synthetic utilities of aryl thiocyanates.
widely used as drugs, dyes and precursors for agrochemicals, as well as proved useful as
intermediates in the synthesis of sulfur-containing heterocycles [21].
The benefits and high importance of nitrogen atom in nature and living organisms such
as amino acids, nucleic acids (DNA and RNA), and proteins have been widely stated in the
literature [22]. Among various methods for the preparation of aryl and heteroaryl thio-
cyanates, the condensation between various N-bearing (hetero)aromatic compounds has
been studied using amount of catalyst and NH4SCN or KSCN in the presence of oxi-
dant. Recently, more-efficient various heterogeneous or homogeneous catalysts such as
Zeolite H-SDUSY Powder (CBV720) [23], SelectfluorTM [24], I2O5 [25], diethyl azodicar-
boxylate [26], CAN [27], Mn(OAc)3.2H2O [28], Thiourea [29], N-thiocyanatosuccinimide
[30], IL-OPPh2 [31], potassium peroxydisulfate/copper (II) sulfate [32], I2/methanol [33],
SBSA [34], Polymer-supported thiocyanate ion [35], SSA and 1-(1- (PSMIM)SCN) [36],
1-Methyl-3-(2-(sulfooxy)ethyl)-1H-imidazol-3-ium thiocyanato [37], FeCl3 [38], Oxone
[39], p-Toluenesulfonic acid [40], HIO3 [41], Visible-Light [42], 2,2ꢀ-Azobenzothiazole
[43], and K2S2O8/DCM [44] have been employed for the synthesis of preparation of aryl
and heteroaryl thiocyanates. Despite their significance, the above-mentioned methods
have their own merits and drawbacks including high cost, long reaction times, low product
yields, generating large amounts of heavy metal wastes, strong acidic or oxidation condi-
tions, difficult removal and recovery and high toxicity. Hence, the introduction of novel
efficient heterogeneous catalyst seems to be a high priority.
In the present study, we described the preparation of a novel isoquinoline sulfonic
acid thiocyanate (isoquinoline-SO3H)SCN via the simple and rapid reaction between iso-
quinoline with chlorosulfonic acid and subsequently the reaction with solution of KSCN
and afforded the corresponding (isoquinoline-SO3H)SCN. Also, isoquinoline sulfonic acid
chloride (isoquinoline-SO3H) Cl as a heterogeneous catalyst was synthesized simply via the

578
S. REZAYATI ET AL.
Scheme 3. Synthetic strategies for thiocyanation of N-bearing (hetero)aromatic compounds using (a)
(isoquinoline-SO3H)SCN and (b) (isoquinoline-SO3H)Cl.
simple and rapid reaction between isoquinoline with chlorosulfonic. The prepared cata-
lysts were characterized using IR, 1H NMR and 13C NMR techniques. Its catalytic activity
was successfully examined for the synthesis of aryl and heteroaryl thiocyanates in high
yields via one-pot reaction of N-bearing (hetero)aromatic compounds in two methods
(Scheme 3).
2. Results and discussion
2.1. Catalyst preparation
The details of the applied strategy for the preparation of the (isoquinoline-SO3H)SCN
iii is illustrated in Scheme 4. As can be seen in Scheme 4, the (isoquinoline-SO3H)SCN
(iii) was simply synthesized in two steps. The (isoquinoline-SO3H)SCN iii was synthe-
sized by the reaction of a solution of isoquinoline i (10 mmol) and sulfonated through
chlorosulfonic acid (10 mmol) in dry CH2Cl2 (10 mL) over a period of 45 min at ice
bath at room temperature. The dry CH2Cl2 was removed under vacuum to give the cor-
responding (isoquinoline-SO3H)Cl ii as a white solid. Then, (isoquinoline-SO3H)Cl ii
was triturated with dry CHCl3 (3 ×10 mL) and dried under vacuum. Finally, in order to
Scheme 4. The synthesis of (isoquinoline-SO3H)SCN.

JOURNAL OF SULFUR CHEMISTRY
579
prepare the isoquinoline sulfonic acid thiocyanate (isoquinoline-SO3H)SCN iii, the solu-
tion of KSCN (10 mmol) in methanol anhydrous was added slowly to the synthesized
(isoquinoline -SO3H)Cl ii over a period of 1 h at room temperature to give the corre-
sponding (isoquinoline-SO3H)SCN iii as a pale orange solid. Eventually, after the synthesis
of (isoquinoline-SO3H)SCN iii, KCl (s) was filtered and methanol was evaporated under
vacuum.
2.2. Catalyst characterizations
The prepared (isoquinoline-SO3H)SCN catalyst was characterized by FT-IR, 1H and 13
C
NMR techniques (see Supplementary). FT-IR spectra of (a) isoquinoline, (b) isoquinoline
sulfonic acid chloride (isoquinoline-SO3H)Cl and (c) isoquinoline sulfonic acid thio-
cyanate (isoquinoline-SO3H)SCN were compared with one another. The FT-IR spectrum
of isoquinoline showed the weak peaks in 3055 cm−1 that was related to the C–H stretching
absorption. One strong band at 1627 cm−1 was related to C = N absorption. In addition,
we assigned the absorption bands at 1457 cm−1 to C = C stretching vibrations. The FT-IR
spectrum of isoquinoline sulfonic acid chloride (isoquinoline-SO3H)Cl showed that the
strong and broad bands were at 2200-3300 cm−1 that was related to O-H of SO3H group,
proving the successful synthesis of (isoquinoline-SO3H)Cl. Also, O-H stretching vibration
overlapped with C–H stretching absorption. On the other hand, the strong band at 1027-
1165 cm−1 was related to O = S=O asymmetric and symmetric stretching modes of the
-SO3H groups. The strong bands at 2057cm−1 were observed clarifying the fact that they
were related to the SCN stretching absorption of (isoquinoline-SO3H(SCN, suggesting the
successful synthesis.
1H and 13C NMR spectra of isoquinoline sulfonic acid thiocyanate (isoquinoline-
SO3H)SCN were indicated. The 1H NMR spectrum of (isoquinoline-SO3H)SCN indicated
8 types of protons. One broad singlet signal was recognized arising from OH groups of -
SO3H at δ = 9.19 ppm. One sharp singlet signal was recognized arising from H of C-1 of
isoquinoline at δ = 9.89 ppm. Two doublets at 8.27 (3J = 8.2 Hz) and 8.64 (3J = 6.2 Hz)
were related to H-4 and H-3 of isoquinoline, respectively. Another doublet at 8.501
(3J = 7.2 Hz) is attributed to aromatic moiety H5 and H8. Also, two triplets at δ = 7.96
and δ = 8.15 are attributed to aromatic moiety protons for C6-H and C7-H. The 13C
NMR spectrum of (isoquinoline-SO3H)SCN indicated 10 distinct signals, which were in
agreement with the proposed structure.
2.3. Catalytic studies
As a part of the present research, we decided to consider the catalytic activity of
(isoquinoline-SO3H)SCN in the thiocyanation of N-bearing (hetero)aromatic compounds
in the presence of H2O2 as a green oxidant in CH3OH (Scheme 3a). In order to optimize
the reaction conditions, the reaction of aniline with H2O2 under solvent-free conditions
was chosen as the model reactions based on various experimental parameters such as cat-
alyst loading, effect temperature, and effect solvent. The results are summarized in Table
1. Initially, the effect of the amount of catalyst was investigated in the presence of H2O2
under solvent-free conditions. In the absence of catalyst, the reaction failure occurred after
200 min (Table 1, entry 1). 0.3 mmol was the most effective condition for this reaction and

580
S. REZAYATI ET AL.
4-thiocyanatoaniline was obtained in 83% yield after 60 min (Table 1, entry 4). The increas-
ing temperature from the room temperature to 100 °C led to a decrease in the time reaction
and product yield (Table 1, entries 8-10).
Then, in another study to have a comparison between effect of various solvents and
solvent-free conditions, the preparation of 4-thiocyanatoaniline was carried out using
diverse solvents including CH3OH, EtOH, H2O/EtOH, DMF, CHCl3, CH2Cl2 and n-
Hexane in the presence of (isoquinoline-SO3H)SCN (0.3 mmol) as heterogeneous catalyst
in various amount of H2O2. Considering the yields of products and reaction time, CH3OH
(3 mL) and H2O2 (0.4 mL) at room temperature proved to be the best choices for the sol-
vent and oxidant, respectively. After an extensive screening of the experimental parameters
Table 1. Optimization of the reaction conditions for the synthesis of 4-thiocyanatoanilinea.
Entry
Catalyst (mmol)
Conditions
H2O2 (mL)
Time (min)
Yield (%)b
1
2
3
4
5
6
7
8
9
-
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
60
80
100
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
200
90
90
60
60
60
60
180
180
160
NR
42
69
83
73
68
71
77
80
57
0.1
0.2
0.3
0.5
0.7
1
0.3
0.3
0.3
10
aReaction conditions: aniline (1 mmol), H2O2 (0.2 mL) in the presence of (isoquinoline-SO3H)SCN under solvent-free condi-
tions.
bYields of isolated products.
Table 2. Optimization of various solvents for the model reactions by using 0.3 mmol of (isoquinoline-
SO3H)SCN as catalyst.
Entry
Catalyst (mmol)
Solvent (3 mL)
H2O2 (mL)
Time (min)
Yield (%)a
1
2
3
4
5
6
7
8
9
10
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
CH3OH
CH3OH
CH3OH
CH3OH
CH3OH
CHCl3
0.2
0.3
0.4
0.5
0.6
0.4
0.4
0.4
0.4
0.4
20
20
10
10
10
1 day
360
180
180
180
85
89
98
91
91
NR
66
NR
37
51
DMF
n-Hexane
CH2Cl2
EtOH
aYields of isolated products

JOURNAL OF SULFUR CHEMISTRY
581
Table 3. Synthesis of aryl and heteroaryl thiocyanates derivatives in the presence of (isoquinoline-
SO3H)SCNa.
Entry
1
Substrate
Product
Time (min)
15
Yield (%)b
92
2
45
89
3
4
45
10
90
98
5
6
20
20
86
87
7
10
90
(continued).
such as catalyst loading, effect temperature, and effect solvent and oxidant, as can be seen in
Tables 1 and 2, the best conditions (time and yield) of thiocyanation of aniline reaction was
obtained when the reaction was performed using 0.3 mmol of (isoquinoline-SO3H)SCN
in the presence of H2O2 (0.4 mL) in CH3OH at room temperature.
To generalize this methodology, we used a various of N-bearing (hetero)aromatic
compounds such as aniline, indole, pyrroles, and their derivatives in the presence of

582
S. REZAYATI ET AL.
Table 3. Continued.
Entry
Substrate
Product
Time (min)
45
Yield (%)b
87
8
9
30
89
10
11
30
-
88
-
aReaction conditions: aniline (1 mmol), H2O2 (0.4 mL) in the presence of (isoquinoline-SO3H)SCN in CH3OH (3 mL) at r.t.
bYields of isolated products
(isoquinoline-SO3H)SCN as a heterogeneous catalyst at room temperature in CH3OH
(Table 3). Many types of N-bearing (hetero)aromatic compounds, electron-withdrawing
and electron-donating were used to obtain the corresponding aryl and heteroaryl thio-
cyanates with a good yield and short reaction time (Table 3).
A plausible mechanism for the one-pot reaction between the aniline and H2O2 in
the presence of (isoquinoline-SO3H)SCN for the synthesis of the corresponding 4-
thiocyanatoaniline is shown in Scheme 5. The initial step involved the generation of SCN−
and H+ ion (isoquinoline-SO3H)SCN in solvent. The next step involved the generation of
peroxonium ion (H3O2+) ion by reaction between H2O2 and (isoquinoline-SO3H)SCN.
+
Subsequently, the condensation of H3O2 ion with SCN was to produce HOSCN, which
in the presence of H+ was able to corresponding thiocyanium ion +SCN and H2O. Finally,
the electrophilic thiocyanation by thiocyanium ion +SCN occurred with aniline to give the
corresponding 4-thiocyanatoaniline.
After the success of (isoquinoline-SO3H)SCN as a reagent in the thiocyanation
of N-bearing (hetero)aromatic compounds, we decided to explore the catalytic of
(isoquinoline-SO3H)Cl as a novel and heterogeneous catalyst for the thiocyanation of
N-bearing (hetero)aromatic compounds (Scheme 3b). Subsequently, to select the best con-
ditions of the reaction, the reaction of aniline with H2O2 under solvent-free conditions was
chosen as the model reactions based on various experimental parameters such as catalyst
loading, effect temperature, effect solvent and oxidant. Based on the optimization of reac-
tion, it can be concluded that 0.4 mmol of (isoquinoline-SO3H)Cl, NH4SCN (1.5 mmol)
with H2O2 (0.4 mL) in CH3OH is the required quantity of catalyst which gave 96% yield in
20 min. In this study, based on the optimal reaction conditions, many types of N-bearing
(hetero)aromatic compounds, electron-withdrawing and electron-donating, were used to

JOURNAL OF SULFUR CHEMISTRY
583
Scheme 5. The plausible mechanism for the preparation of 4-thiocyanatoaniline by (isoquinoline-
SO3H)SCN.
obtain the corresponding aryl and heteroaryl thiocyanates with a good yield and short
reaction time (Table 4).
To illustrate the practicability of current method, the synthesis of 4-thiocyanatoaniline
was scaled up (Scheme 6). A gram-scale reaction using of aniline (15 mmol, 1.39 g),
6 mL of H2O2, and 0.3 mmol of (isoquinoline-SO3H)SCN was performed to isolate 4-
thiocyanatoaniline in 60%.
The reusability of the catalyst is an important issue to the heterogeneous catalysts and
commercial applications. The reusability of the (isoquinoline-SO3H)Cl heterogeneous cat-
alyst was studied in the optimized reaction conditions for the reaction of aniline and
NH4SCN in the presence of H2O2 in methanol (Figure 1). As observed in Figure 1, the
catalyst was separated and then washed with CHCl3 several times to remove the residual
product. Next, the reused catalyst was dried at room temperature for further uses. As
observed in Figure 1, the yields and reaction times were reported for each step of recovery,
and the catalyst was used for more than 7 times.
To show the catalytic properties of our novel (isoquinoline-SO3H)SCN, its catalytic
activity was compared (yield, short reaction time and solvent) with that of several other
potential catalysts, such as SelectfluorTM [24], I2O5 [25], DEAD [26], CAN [27], potassium
peroxydisulfate/copper (II) sulfate (K2S2O8-Cu(II)) [32], Iodine [33], FeCl3 [38], Aerobic
metal-free [42], SBSA and SSA [45], H3PO4@nano SiO2 and Nano SiO2 [46], Graphite
electrode [47], SiO2@[Pyridine-SO3H]SCN and [PSA]Cl [48] (Table 5). As it is evident

584
S. REZAYATI ET AL.
from Table 5, our results indicated that the novel catalyst is superior to many of the others
in terms of yield and shorter reaction times.
3. Conclusion
Briefly, we described an efficient and simple strategy to the synthesize isoquinoline sul-
fonic acid thiocyanate (isoquinoline-SO3H)SCN and isoquinoline sulfonic acid chloride
(isoquinoline-SO3H)Cl as a novel and heterogeneous catalyst. The structure of the pre-
1
pared (isoquinoline-SO3H)SCN was characterized by IR, H NMR and 13C NMR tech-
niques. The catalytic activity of (isoquinoline-SO3H)SCN (0.3 mmol) and (isoquinoline-
SO3H)Cl (0.4 mmol) was investigated in the thiocyanation of N-bearing (hetero)aromatic
compounds under mild conditions in methanol at room temperature. Excellent yields and
short reaction time of the corresponding aryl and heteroaryl thiocyanates derivatives were
Table 4. Synthesis of aryl and heteroaryl thiocyanates derivatives in the presence of (isoquinoline-
SO3H)Cla.
Entry
1
Substrate
Product
Time (min)
20
Yield (%)b
91
2
3
60
60
88
90
96
4
5
20
25
90
(continued).

JOURNAL OF SULFUR CHEMISTRY
585
Table 4. Continued.
6
30
15
90
92
7
8
45
35
20
85
90
91
9
10
11
–
–
aReaction conditions: aniline (1 mmol), H2O2 (0.4 mL) in the presence of (isoquinoline-SO3H)Cl in CH3OH (3 mL) at r.t.
bYields of isolated products
Scheme 6. Gram scale synthesis of 4-thiocyanatoaniline.
obtained. Operational simplicity, simple filtration, cheap and chemically stabile reagents,
eco-friendly procedure, and use of a commercially available materials make our catalyst a
promising candidate for potential applications in some organic reactions.
4. Experimental
4.1. General
All chemicals were purchased from Merck or Fluka Chemical Companies. Products were
separated and purified by different chromatographic techniques and were identified by

586
S. REZAYATI ET AL.
Figure 1. Recyclability of catalyst.
Table 5. Comparing catalytic activity of (isoquinoline-SO3H)SCN and (isoquinoline-SO3H)Cl with previ-
ously reported methods in the synthesis of aryl and heteroaryl thiocyanate derivatives.
Entry
Catalyst
SelectfluorTM
I2O5
DEAD
CAN
K2S2O8-Cu(II)
Iodine
FeCl3
Aerobic metal-free
SBSA
Conditions
CH3CN, r.t.
Time (min)
Yield (%)a
Ref.
1
2
3
4
5
6
7
8
9–20
0.6-480
6–150
15
60–300
20–50
180–300
18–48 h
10–270
7–75
0.25-8 h
0.25-8 h
25–90
20–70
10–120
10–45
15–60
78–98
59–96
75–91
32–99
57–86
82–96
81–92
73–98
71–92
71–95
38–90
32–90
10–96
82–93
85–95
86–98
85–96
[24]
[25]
[26]
[27]
[28]
[33]
[38]
[42]
[45]
[45]
[46]
[46]
[47]
[48]
[48]
–
CH3OH, r.t.
CH3CN, NH4SCN, r.t.
CH3OH, NH4SCN, r.t.
NH4SCN, CH3CN, r.t.
NH4SCN, CH3OH, r.t.
NH4SCN, CH2Cl2, r.t.
visible light, NH4SCN, air
KSCN, H2O, r.t.
KSCN, UHP, H2O, r.t.
solvent-free, NH4SCN, 70 °C
solvent-free, NH4SCN, 70 °C
CH3OH, NH4SCN,
9
10
11
12
13
14
15
16
17
SSA
H3PO4@nano SiO2
Nano SiO2
Graphite electrode
SiO2@[Pyridine-SO3H]SCN
[PSA]Cl
(isoquinoline-SO3H)SCN
(isoquinoline-SO3H)Cl
EtOH:H2O, H2O2, r.t.
EtOH:H2O, H2O2, NH4SCN,
CH3OH, H2O2, r.t.
CH3OH, NH4SCN, H2O2, r.t
–
aYields of isolated products
1
comparing their IR, H and 13C NMR, with those reported for the authentic samples.
The progress of the reactions and the purity check of the final products were carried
out by thin layer chromatography (TLC) using silica gel precoated aluminium sheets (60-
120 mesh; Merck) and the visualization was conducted with ultraviolet light at 365 and
254 nm.1H NMR (250.13 MHz) and 13C NMR (62.9 MHz) spectra were recorded on a
Bruker Avance spectrometer using DMSO-d6 as the solvent and TMS as an internal stan-
dard. IR spectra were recorded on a Frontier Fourier transform infrared (FT-IR) (Perkin
Elmer) spectrometer using a KBr disk.

JOURNAL OF SULFUR CHEMISTRY
587
4.1.1. General procedure for the preparation of the isoquinoline sulfonic acid
thiocyanate (isoquinoline-SO3H)SCN
In the first step, a solution of chlorosulfonic acid (5 mmol) in dry CH2Cl2 (10 mL) was
added dropwise to a solution of isoquinoline (5 mmol) in dry CH2Cl2 (10 mL) under stir-
ring for 45 min at room temperature. The resulting white solid was obtained by filtration,
washed with 10 mL of CHCl3 and dried in vacuum to obtain the isoquinoline sulfonic acid
chloride (isoquinoline-SO3H)Cl (Scheme 4). In the final step, the obtained isoquinoline
sulfonic acid chloride (isoquinoline-SO3H)Cl was dissolved in 10 mL of methanol anhy-
drous under stirring, then, a solution of KSCN (5 mmol) in methanol anhydrous was added
slowly for 1 h to the reaction mixture which was stirred at room temperature. The resulting
pale orange solid was obtained by filtration of KCl (s) and methanol was evaporated under
vacuum. Then, the final isoquinoline sulfonic acid thiocyanate (isoquinoline-SO3H)SCN
was washed with 10 mL of petroleum ether and dried in vacuum.
Pale orange solid; yield: 95%; mp: 138–140 °C. FT-IR (KBr) νmax/cm−1: 2200–3300
1
(OH), 2057 (SCN), 1627 (C = N), 1457 (C = C), 1027–1167 cm−1 (O = S=O). H
NMR (250.13 MHz, DMSO-d6): δ = 7.96 (t, 1H, Ar-H), 8.15 (t, 1H, Ar-H), 8.27 (d, 1H,
H
3J = 8.2 Hz, Ar-H isoquinoline), 8.51 (d, 2H, 3J = 7.2 Hz, Ar-H), 8.64 (d, 1H, 3J = 6.2 Hz,
Ar-H isoquinoline), 9.19 (brs, 1H, OH), 9.89 (s, 1H, Ar-H isoquinoline). 13C NMR
(62.9 MHz, DMSO-d6): δ = 108.5 (SCN), 125.6 (CH-4), 127.3 (CH-5), 127.7 (CH-7),
C
130.9 (CH-8), 131.1 (C-9), 132.2 (CH-6), 136.9 (C-10), 138.5 (CH-3), 147.9 (CH-1) ppm.
4.1.2. General procedure for the thiocyanation of N-bearing (hetero)aromatic
compounds using (isoquinoline-SO3H)SCN
N-bearing (hetero)aromatic compounds (1 mmol) and (isoquinoline-SO3H)SCN (0.3
mmol, 0.080 g) in methanol (3 mL) were stirred at room temperature for 5 min. Then,
H2O2 30% (0.4 mL) was added. The progress of the reaction was monitored by TLC, using
eluent: n-Hexane/EtOAc, 9:1. After completion of the reaction, the reaction mixture was
quenched and extracted with CHCl3 (2×10 mL). Anhydrous Na2SO4 (2 g) was added to
the organic layer and filtered off after 20 min, and the chloroform was removed under
vacuum. The pure products were obtained in 82–93% yield.
4-thiocyanatoaniline: Solid blue; yield: 92%; FT-IR (KBr) νmax/cm−1: 3349–3420 (-
1
NH2), 2146 (SCN), 1496 (C = C). H NMR (250.13 MHz, DMSO-d6): δ = 5.75 (s,
H
2H, NH2), 6.53 (d, J = 8.2 Hz, 2H, Ar-H), 7.29 (d, J = 8.0 Hz, 2H, Ar-H). 13C NMR
3
3
(62.9 MHz, DMSO-d6): δ = 105.2 (SCN), 114.8 (C), 115.5 (2 CH), 135.2 (2 CH), 151.8
C
(C) ppm.
4.1.3. General procedure for the thiocyanation of N-bearing (hetero)aromatic
compounds using (isoquinoline-SO3H)Cl
N-bearing (hetero)aromatic compounds (1 mmol), NH4SCN (1.5 mmol) and (isoquino
line-SO3H)Cl (0.4 mmol, 0.097 g) in methanol (3 mL) were stirred at room temperature
for 5 min. Then, H2O2 30% (0.4 mL) was added. The progress of the reaction was mon-
itored by TLC, using eluent: n-Hexane/EtOAc, 9:1. After completion of the reaction, the
reaction mixture was quenched and extracted with CHCl3 (2×10 mL). Anhydrous Na2SO4
(2 g) was added to the organic layer and filtered off after 20 min, and the chloroform was
removed under vacuum. The pure products were obtained in 85–96% yield.

588
S. REZAYATI ET AL.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
This work was supported by the ‘Iran National Science Foundation INSF’ and the University of
Zanjan. The present work was from PhD thesis by Sobhan Rezayati.
ORCID
Sobhan Rezayati http://orcid.org/0000-0001-8940-2927
Ali Ramazani http://orcid.org/0000-0003-3072-7924
Elham Ezzatzadeh http://orcid.org/0000-0002-6271-7694
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