Synthesis of 4-aryl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-selones via a three-component condensation of 6-methoxybenzothiazol-2-ylamine, potassium selenocyanate and an acyl chloride

Article abstract of DOI:10.1080/10426507.2020.1715405

A simple, one-pot synthesis of six 4-aryl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-selones has been achieved in moderate to good yields via a three-component condensation of 6-methoxybenzothiazol-2-ylamine, potassium selenocyanate and variously substitut

Full text of DOI:10.1080/10426507.2020.1715405

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: https://www.tandfonline.com/loi/gpss20
Synthesis of 4-aryl-7-methoxy-9-thia-
[1,3,4a]triazafluorene-2-selones via a
three-component condensation of 6-
methoxybenzothiazol-2-ylamine, potassium
selenocyanate and an acyl chloride
Majid Ehsanfar, Mohammad H. Mosslemin & Alireza Hassanabadi
To cite this article: Majid Ehsanfar, Mohammad H. Mosslemin & Alireza Hassanabadi (2020):
Synthesis of 4-aryl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-selones via a three-component
condensation of 6-methoxybenzothiazol-2-ylamine, potassium selenocyanate and an acyl chloride,
Phosphorus, Sulfur, and Silicon and the Related Elements, DOI: 10.1080/10426507.2020.1715405
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PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
https://doi.org/10.1080/10426507.2020.1715405
Synthesis of 4-aryl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-selones via a three-
component condensation of 6-methoxybenzothiazol-2-ylamine, potassium
selenocyanate and an acyl chloride
a
a
b
Majid Ehsanfar , Mohammad H. Mosslemin , and Alireza Hassanabadi
a
b
Department of Chemistry, Yazd Branch, Islamic Azad University, Yazd, Iran; Department of Chemistry, Zahedan Branch, Islamic Azad
University, Zahedan, Iran
ABSTRACT
ARTICLE HISTORY
A simple, one-pot synthesis of six 4-aryl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-selones has been
achieved in moderate to good yields via a three-component condensation of 6-methoxybenzothia-
zol-2-ylamine, potassium selenocyanate and variously substituted benzoyl chlorides in acetone at
room temperature.
Received 3 November 2019
Accepted 9 January 2020
KEYWORDS
4
-Aryl-7-methoxy-9-thia-
[
134a]triazafluorene-2-
GRAPHICAL ABSTRACT
selones; benzoyl chlorides;
potassium selenocyanate; 6-
methoxybenzothiazol-
2
-ylamine
Introduction
Selenobenzophenone reversibly dimerizes. It is known to
undergo cycloaddition with 1,3-dienes in a reaction similar to
the Diels-Alder reaction.
Bridgehead nitrogen heterocycles are of interest because they
constitute an important class of natural and synthetic prod-
ucts, many of which exhibit useful biological activity.
16
The current interest in selenium-containing organic com-
pounds stems from their remarkable synthetic and biological
1
,2
Many triaza analogs of polycyclic aromatic compounds that
feature a bridgehead nitrogen have a long history of wide-
spread use as precursors to construct functional materials
such as antibacterial agents, pesticides, active dyes, encapsu-
lation resins of integrated circuits, and structural adhesives
for advanced carbon-fiber composites in the aerospace
17–21
functions.
The first synthesis of acyl isoselenocyanates,
which were generated by the reaction of acyl chlorides and
2
2
potassium selenocyanate, has been described by Douglas.
Recently, a few synthesis of heterocycles from acyl isoseleno-
23–25
cyanates were reported.
Herein, we describe a synthesis
3–7
of a new series of 4-aryl-7-methoxy-9-thia-[1,3,4a]triaza-
industry. As a result, a number of reports of their synthe-
23
8–12
fluorene-2-selones using a reported method.
sis have appeared in the literature,
but most of them
require forcing conditions, long reaction times and complex
synthetic pathways.
In chemistry, a selenone is the structural analog of a
ketone where selenium replaces oxygen. Selenium-77, is one
of the isotopes of selenium that is stable and naturally occur-
ring, so selone-containing chemicals can be analyzed by
Results and discussion
23
A recent report described the synthesis of a series of aryl
triazanaphthalene-selones by the reaction at room tempera-
ture in solvent acetone between 2-aminopyridine, an acyl
nuclear magnetic resonance spectroscopy (NMR). They can chloride and potassium selenocyanate (KSeCN). We thought
77
13
be used as chiral derivatizing agents for Se-NMR. Chiral that a synthesis of some benzo analogs of the aryl triaza-
oxazolidineselones can be used for stereoselective control of naphthalene-selones, 4-aryl-7-methoxy-9-thia-[1,3,4a]triaza-
aldol reactions, analogous to the Evans aldol reaction that fluorene-2-selones (4) might be simply achieved by a similar
77
uses oxazolidinones, which allows Se-NMR to be used to reaction in which 2-aminopyridine was replaced by 6-
14
determine the diastereomeric ratio of the aldol product.
In contrast to analogous structures with lighter chalcogens,
selones exhibit greater steric and electronic stabilization.
methoxybenzothiazol-2-ylamine (1) (Scheme 1).
So it proved, and a series of six such compounds were
prepared in good yields by using a variety of substituted
15
CONTACT Mohammad H. Mosslemin
ß 2020 Taylor & Francis Group, LLC
mhmosslemin@gmail.com
Department of Chemistry, Yazd Branch, Islamic Azad University, Yazd, Iran

2
M. EHSANFAR ET AL.
benzoyl chlorides (2; Ar ¼ various) in reaction with 6-
methoxybenzothiazol-2-ylamine (1) and KSeCN (3) acyl isoselenocyanate 5 followed by addition of 6-methoxy-
Table 1).
benzothiazol-2-ylamine 1 to generate 6. The cyclization of
It is conceivable that the reaction starts with formation of
(
The structures of compounds 4a-g were deduced from intermediate 6 affords 7, which is converted into 4 by elim-
1
their elemental analysis and their IR, H NMR, 13C NMR
ination of water (Scheme 2).
1
and mass spectra. The H NMR spectrum of compound 4a
was simple and exhibited a single sharp line readily recog-
nized as arising from a methoxy (d ¼ 3.84 ppm). Aromatic Experimental
protons resonate as multiples at d ¼ 7.05–7.26 ppm. The
Melting points were determined with an Electrothermal
mass spectra of compounds 4a–f are fairly similar and dis-
play molecular ion peaks. For example, the mass spectrum
of compound (4a) showed a molecular ion peak at 372 con-
firming that it is a (1:1:1) adduct of, 6-methoxybenzothiazol-
9
100 apparatus and are uncorrected. Elemental analysis for
C and H were performed using a Heraeus CHN-O-Rapid
analyzer. Mass spectra were recorded on a FINNIGAN-
MAT 8430 mass spectrometer operating at an ionization
potential of 70 eV. IR spectra were recorded on a Shimadzu
IR-470 spectrometer. NMR spectra were obtained on a
2
-ylamine, benzoyl chloride and potassium selenocyanate.
The IR spectrum of compound 4a also supported the sug-
gested structure exhibiting strong absorption bands at
1
ꢀ
1
ꢀ1
Brucker DRX 500 Avance spectrometer ( H NMR at 500 Hz,
1
595 cm
groups. The 13C NMR spectrum of compound 4a showed
4 distinct resonances in agreement with the proposed standard. Chemical shifts (d) are given in ppm. All of the
structure. The selone 13C resonances of compounds 4 were chemicals used in this study were purchased from Merck
for the C ¼ N and 1290 cm
for the C ¼ Se
1
3C NMR at 125 Hz) in d -DMSO using TMS as an internal
6
1
26
observed at 165.3–169.6 ppm.
The mechanism of the reaction is probably similar to that ther purification. The Supplemental Materials con-
published by Yavari et al.
and Fluka (Buchs, Switzerland) and were used without fur-
23
tains sample
Caution! All of the reactions involving selenium-containing
compounds should be carried out in a well-ventilated hood.
Table 1. Yields of a series of 4-aryl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-
selones (4) prepared from 6-methoxybenzothiazol-2-ylamine (1), an acyl chlor-
ide (2) and KSeCN (3) (Scheme 1).
General procedure
To a solution of potassium selenocyanate (1 mmol) in dry
acetone (3 mL) was added acyl chloride (1 mmol) in dry
acetone (3 mL). The reaction mixture was stirred at r.t. for
b
ꢁ
4
Ar
%Yield
m.p. ( C)
a
b
c
4
d
e
C
6
H
5
78
83
81
%Yield
92
90
75
118–120
189–191
4-C1C
4-BrC
Ar
3-O
4-O
4-CH
6
H
4
6
H
4
196–198 10 min. 6-methoxybenzothiazol-2-ylamine (1 mmol) in dry
b
ꢁ
m.p. ( C)
acetone (4 mL) was added to the mixture. The progress of
2
NC
NC
6
H
H
4
181–183
225–227 the reaction was monitored by TLC. After completion of the
2
6
4
f
3
6
C H
4
128–130
reaction, the resulting precipitate was collected by filtration
on a Buchner funnel and washed with cold water (20 mL)
ꢂ
Yields refer to the pure isolated products
O
Ar
N
Ar
Cl
N
2
+
acetone, r. t.
6 h
N
N
O
S
1
NH2
O
S
Se
KSeCN
4
3
Scheme 1. Three-component condensation of 6-methoxybenzothiazol-2-ylamine, variously substituted benzoyl chlorides and potassium selenocyanate.
Se
H
H
O
N
N
1
S
2
+ 3
Ar
N
C
Se
O
O
5
N
Ar
6
Se
N
N
H
-H O
N
S
2
4
Ar
OH
O
7
Scheme 2. Proposed mechanism for 4.

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
3
and recrystallized from EtOH to afford the pure aromatic); 13C NMR(ppm): d 55.29 (OCH ), 104.5, 114.9,
3
title compounds.
120.4, 123.2, 127.4, 128.5, 129.5, 132.2, 137.6, 149.3, 155.7,
56.1, and 165.3; Anal. Calcd. for C H N O SSe: C, 46.05;
1
16
10 4 3
H, 2.42; N, 13.43. Found: C, 46.15; H, 2.55; N, 13.53%; MS
m/z, %): 417 (9).
4
-Phenyl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-
(
selone (4a)
ꢁ
ꢀ1
Yellow powder; m.p. 118–120 C; IR (KBr) (ꢀ
1
cm ):
max
4
-p-Tolyl-7-methoxy-9-thia-[1,3,4a]triazafluorene-2-
1
664, 1595, 1556, 1462, 1290, 1117; H NMR(ppm): d 3.84
3H, s, OCH ), 7.05–8.26 (8H, m, 8CH aromatic); 13C
NMR(ppm): d 55.45 (OCH ), 104.5, 114.8, 120.8, 128.1, Yellow powder; m.p. 128-130 C; IR (KBr) (ꢀmax cm ):
28.3, 128.4, 128.6, 129.1, 132.5, 132.6, 155.2, 156.1 and
67.1; Anal. Calcd. for C H N OSSe: C, 51.62; H, 2.98; N,
selone (4f)
(
3
ꢁ
ꢀ1
3
1
1
666, 1604, 1550, 1468, 1273, 1116; H NMR(ppm): d 2.40
1
1
1
3
(3H, s, CH ), 3.82 (3H, s, OCH ), 7.04–8.15 (7H, m, 7CH
3
3
16
11 3
aromatic); 13C NMR(ppm): d 20.7 (CH ), 55.29 (OCH ),
1.29. Found: C, 51.75; H, 3.09; N, 11.40%; MS (m/z, %):
72 (6).
3
3
1
1
04.3, 114.6, 120.6, 127.9, 128.8, 129.0, 129.8, 139.4, 142.3,
42.7, 143.5, 155.9 and 169.6; Anal. Calcd. for
C H N OSSe: C, 52.85; H, 3.39; N, 10.88. Found: C, 52.94;
H, 3.60; N, 11.01%; MS (m/z, %): 386 (5).
17
13 3
4
-(4-Chlorophenyl)-7-methoxy-9-thia-[1,3,4a]
triazafluorene-2-selone (4b)
ꢁ
ꢀ1
Yellow powder; m.p. 189–191 C; IR (KBr) (ꢀ
1
cm ):
max
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658, 1596, 1563, 1471, 1311, 1148; H NMR(ppm): d 3.81
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[
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1
3
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3
659, 1596, 1552, 1424, 1338, 1266, 1125; H NMR(ppm): d
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4
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