NCS/TBHP promoted C2 arylation of benzothiazoles with aldehydes in DMSO

Article abstract of DOI:10.1016/j.tetlet.2020.151807

A N-chlorosuccinimide catalyzed oxidative synthesis of 2-aryl benzothiazole from benzothiazoles and aryl aldehydes using tert-butyl peroxybenzoate as an oxidant in dimethyl sulfoxide (DMSO) has been developed in moderate to good yields. Solvent DMSO as a strong Lewis base plays an efficient role in the reaction. Various substrates were tolerated under optimized conditions affording the arylated products in 12–94% yields for 28 examples. Additionally, acylated benzothiazoles were produced with 4 examples.

Full text of DOI:10.1016/j.tetlet.2020.151807

Journal Pre-proofs
NCS/TBHP promoted C2 Arylation of Benzothiazoles with Aldehydes in
DMSO
Wen-Xiu Xu, Fei-Xia Ye, Xing-Hai Liu, Jian-Quan Weng
PII:
S0040-4039(20)30242-2
DOI:
Reference:
https://doi.org/10.1016/j.tetlet.2020.151807
TETL 151807
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Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
23 January 2020
2 March 2020
6 March 2020
Please cite this article as: Xu, W-X., Ye, F-X., Liu, X-H., Weng, J-Q., NCS/TBHP promoted C2 Arylation of
Benzothiazoles with Aldehydes in DMSO, Tetrahedron Letters (2020), doi: https://doi.org/10.1016/j.tetlet.
2020.151807
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Tetrahedron Letters
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NCS/TBHP promoted C2 Arylation of Benzothiazoles with Aldehydes in DMSO
Wen-Xiu Xu, Fei-Xia Ye, Xing-Hai Liu, Jian-Quan Weng*
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, P. R. China
ARTICLE INFO
ABSTRACT
A N-chlorosuccinimide catalyzed oxidative synthesis of 2-aryl benzothiazole from benzothiazoles and
aryl aldehydes using tert-butyl peroxybenzoate as an oxidant in dimethyl sulfoxide (DMSO) has been
developed in moderate to good yields. Solvent DMSO as a strong Lewis base plays an efficient role in
the reaction. Various substrates were tolerated under optimized conditions affording the arylated
products in 12–94% yields for 28 examples. Additionally, acylated benzothiazoles were produced with
4 examples.
Article history:
Received
Received in revised form
Accepted
Available online
Keywords:
Benzothiazoles
Aldehydes
Arylation
2018 Elsevier Ltd. All rights reserved.
NCS/TBHP
Introduction
2-Aryl benzothiazoles have been well known with various
pharmaceutical applications, such as benzothiazole amphiphile
(BAM)1 and benzazole scaffold (ThT, [3H]PIB, BFC)2 related to
the Alzheimer’s disease, chloronitrobenzamide (CNB) for
Human African Trypanosomiasis (HAT) antiparasitics,3 2-(3,4-
Dimethoxyphenyl)-5-fluorobenzothiazole (GW 610) possessing
antitumor activity4 (Fig. 1)
thiobenzanilides,10 which are used as precursors to synthesize 2-
substituted benzothiazoles. Besides, transition-metal catalyzed
arylation of benzothiazole with aryl halides,11 aryl boronic
acids,12 organosilanes,13 sodium sulfinats,14 aldehydes,15 benzylic
alcohols,15d phenylacetic acids16 are also effective routes for their
construction. However, these methods need prefunctionalized
reactants which are costly and not easily available,17 and
complete removal of trace amounts of the residual heavy metals
from the desired products remains costly and challenging.18
Alternatively, 2-aryl benzothiazoles can also be developed
through multi-component oxidative annulation including various
sulfur source, such as elemental sulfur19 and NH4SCN.20
Therefore, it is of great importance to develop efficient methods
to construct 2-aryl benzothiazoles from simple starting materials
under transition-metal free condition. In 2012, Tan and co-
workers reported a K2S2O8-catalyzed arylation of benzothiazoles
with aryl aldehydes or glyoxylic acids, which are known to form
aldehydes at a relative elevated temperature (Scheme 1A).21 It
has been reported that the peroxydisulfate ion (S2O82-) is the most
powerful oxidant among other peroxygen families of
compounds.22 Thus, the strong oxidant K2S2O8 seriously limit the
utility of such method in organic synthesis requiring selectivity.
Two year later, Cui and co-workers published a KI-catalyzed
arylation of benzothiazoles with aldehydes in H2O (Scheme
1B).17 Interestingly, H2O is essential in both works mentioned
above and the yields decreased dramatically while H2O was
removed (Tan’s work) or the organic solvent such as acetonitrile
(MeCN) or dimethyl sulfoxide (DMSO) was added (Cui’s work).
As Cui reported, the homogeneous solution was not suitable for
this method.17 However, a lot of works have been reported that
DMSO was an optimized solvent for synthesis of 2-aryl
benzothiazoles initiated not only by organic catalyst9 but also by
inorganic catalyst,13 even mediated by a very similar catalyst
S
S
N
N
N
O
N
OH
H
5
ThT
BAM
NH
3H
H2C
HO
S
N
Cl
N
NH
O
N
NO2
S
NH
[3H]PIB
N
CNB
N
N
O
F
N
S
S
N
O
O
O
GW 610
BFC
Fig. 1. Pharmaceutical applications of 2-aryl benzothiazole
derivatives.
Therefore, development of efficient synthetic strategies for
2-aryl benzothiazoles has received much attention. Traditional
methods for their syntheses mostly depend on condensation of 2-
aminothiophenols,5-6
thiophenols,9
and
2-haloanilides,7
intramolecular
2-halonitroarene,8
cyclization of

2
Tetrahedron Letter
(A) Yang and co-workers' work
O
Table 1. Optimization of reaction conditions.
O
oxidant
N
S
radical initiated reagent
N
S
H
H
R2
N
S
N
K2S2O8
H O
solvent
R1
R1
R2
3aa
1a
2a
O
S
DMSO :
= 2 : 1
2
31 examples
up to 74% yield
100 °C
HOOC
Oxidant
(eq.)
Additive (mol
%)
Solvent
Yield
R2
Entry
(mL)
DMSO
MeCN
H2O
(%)b
33
(B) Gao and co-workers' work
1
2
TBHP (2)
TBHP (2)
TBHP (2)
TBHP (2)
DTBP (2)
aq H2O2 (2)
TBHP (2)
TBHP (1)
TBHP (3)
TBHP (2)
TBHP (2)
TBHP (2)
TBHP (2)
TBHP (2)
TBHP (2)
none
NCS (30)
NCS (30)
NCS (30)
NCS (30)
NCS (30)
NCS (30)
NBS (30)
NCS (30)
NCS (30)
NCS (20)
NCS (40)
NCS (30)
NCS (30)
NCS (30)
NCS (30)
NCS (30)
NCS (30)
N
O
14
N
R1
TBHP, KI
R1
H
S
R2
S
R2
H2O
3
N.D.
28 examples
up to 79% yield
N2, 100 °C
4
DCE
19
N.D.
(C) Siddaraju and co-workers' work
O
5
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
R1
NCS, TBHP in decane
N
6
N.D.
N.D.
12
R1
H
R2
N
DCE
7
R2
O
100 °C
35 examples
up to 90% yield
8
This work
9
27
O
N
R1
10
11
12
13
14
15
16
17
15
R2
H
S
R2
N
S
R1
NCS, 70% TBHP
23
7c
29d
42e
53e,f
N.D.e,f
51e,f,g
28 examples
up to 94% yield
DMSO
O
N2, 120 °C
O
N
S
H
R3
R3
4 examples
up to 78% yield
Scheme 1. Reactions between heteroarenes and aldehydes.
system.19a Accordingly, we envisioned that MeCN or DMSO as
aprotic solvents might play significant roles in the reaction. In
addition, N-chlorosuccinimide (NCS) was a useful radical
initiator that has been used in several organic synthetic pre-
activation processes.23 Among these methods, Siddaraju and
Prabhu described that NCS could promote tert-butyl
peroxybenzoate (TBHP) to form a hydroxyl radical and a tert-
butoxyl radical, which abstracts the hydrogen from the
benzaldehyde to form an acyl radical followed by synthesis of
acylated heteroarenes (Scheme 2C).23 Inspired by this work, we
envisioned that NCS may also promote the oxidative coupling of
benzothiazoles with benzaldehydes in the presence of TBHP to
produce 2-aryl benzothiazoles via a similar initial radical step.
Herein, we wish to report our study in detail.
TBHP (2)
aReaction conditions: 1a (1.5 eq., 0.56 mmol), 2a (0.37 mmol), oxidant (0.74
mmol), additive (0.11 mmol) in solvent (0.5 mL) at 120 °C for 6.5 h. bisolated
c
d
e
yield. reaction conducted at 110 ℃. reaction conducted at 140 ℃. for 12 h.
funder N2 atmosphere. gram-scale reaction. N.D. = not detected, DCE = 1,2-
g
dichloroethane, DTBP
=
di-tert-butyl peroxide, TBHP
=
tert-butyl
hydroperoxide, NBS = N-bromosuccinimide, NCS = N-chlorosuccinimide,
TBAB = tetra-n-butylammonium bromide, TBAI = tetra-n-butylammonium
iodide.
1, entries 5 and 6), and the case with NBS did not afford any
target product (Table 1, entry 7). Also, we changed the amount
of oxidant and additive, but poorer yields were obtained in all
these cases (Table 1, entries 9–11). Furthermore, the yield
declined with different degree when the reaction temperature was
decreased to 110 °C or increased to 140 °C (Table 1, entries 12–
13). And a reasonable increase in the yield of the product 3a was
observed when the reaction time was increased from 6.5 h to 12 h
(Table 1, entry 14). Further investigation suggested that the
atmosphere was very important for this reaction. Performing the
reaction under N2 atmosphere resulted in 11% further
enhancement in the yield (Table 1, entry 15). And no product
was observed in the absence of TBHP (Table 1, entry 16). Thus,
the reaction was generally completed within 12 h at 120 °C under
N2 atmosphere using 5.5 M TBHP solution in decane (2 eq.) and
NCS (30 mol %) (Table 1, entry 15). Besides, to demonstrate the
scalability of the method, we performed a gram-scale reaction of
1a (15 mmol) with 2a (10 mmol) (Table 1, entry 17).
Gratifyingly, the efficiency of this method was not obviously
affected, and the target product 3aa was obtained in 51% yield.
With these optimized conditions in hand, we examined the
scope of substrates. As shown in Table 2, the reactions with
benzaldehydes bearing a -Me or -OMe at their ortho-, meta- and
para- positions gave the corresponding arylated products in 53-
Results and discussion
We commenced our investigation by choosing
benzothiazole (1a) with 4-methylbenzaldehyde (2a) as model
substrates mediated by 5.5 M TBHP solution in decane and NCS
in DMSO at 120 °C for 6.5 h (Table 1). To our delight, the
arylated benzothiazoles 3aa was obtained in 33% yield. Next, we
screened various solvents. When another polar aprotic solvent
MeCN was tested as the solvent, the desired product was
observed in 14% yield (Table 1, entry 2). However, the target
product was not obtained when polar protic solvent H2O as the
solvent (Table 1, entry 3). Besides, the reaction using non-polar
aprotic solvent N,N-dimethylformamide (DCE) also provided
product in 19% yield simultaneously (Table 1, Entry 4). These
results show that protic solvent inhibited the reaction, on the
contrary, aprotic solvents could promote the reaction. Among
them, DMSO as one of the aprotic solvents was superior as we
expected (Table 1, entry 1). Thus, we speculated that DMSO as a
strong Lewis base plays an efficient role in the reaction,24 for
example, there might be hydrogen bonds between substrates and
DMSO and that could be beneficial to the H-atom-transfer (HAT)
in the reaction. In addition, other oxidants, such as DTBP and
H2O2 aqueous solution, were useless under the condition (Table
72
%
yield (Table 2, 3aa-3af). Besides, 3,4-
dimethoxybenzaldehyde and 3,4,5-trimethoxybenzaldehyde also
afforded the target products in 44% and 71% yield, respectively
(Table 2, 3ag-3ah), but no desired product was observed with
2,5-dimethoxybenzaldehyde (Table 2, 3ai). The halogenated

Table 2. Scope of substituted benzaldehydes.
Table 3. Scope of substituted benzothiazoles and substituted
O
benzaldehydes.
N
N
S
NCS, TBHP
H
O
R
N
S
DMSO, 120 °C, N2
N
R
R1
NCS, TBHP
H
R1
R2
3
1a
2
S
R2
DMSO, 120 °C, N2
S
3
1
2
MeO
N
N
N
N
S
O
S
S
O
S
N
N
S
Cl
N
3aa
, 53 %
3ab
3ac
, 64 %
, 72 %
3ad
, 66 %
S
, 37 %
N
OMe
OMe
OMe
O2N
OMe
OMe
S
N
S
N
S
N
N
S
3bc
, 94 %
3ba
3bb
, 80 %
OMe
S
N
S
N
OMe
Cl
3af
3ag
, 64 %
F
, 44 %
Cl
3ae
, 54 %
MeO
3ah
, 71 %
S
NC
S
MeO
O2N
3bd
, 12 %
3be, 90 %
OMe
3bf
, N.D.
N
N
S
N
N
OH
HO
S
N
S
N
N
S
3ak
S
3aj
OMe
OH
, 88 %
Br
, 74 %
3al
, 70 %
3ai
, N.D.
S
S
O2N
O2N
O2N
Br
3bg
3bh, N.D.
3bi
, N.D.
, N.D.
N
S
N
N
S
N
S
Br
Cl
Br
S
3an
N
S
N
N
S
, 80 %
HO
3ao
, 34 %
3am
3ap
, 36 %
, 68 %
Br
Cl
S
O2N
O2N
N
S
N
S
N
S
N
S
3bl
, 19 %
3bj
, 23 %
3bk
, N.D.
Cl
CF3
tBu
Br
N
S
N
S
3aq
, N.D.
3ar
, 71 %
3at
3as
, 75 %
, 84 %
O2N
NO2
O
N
S
MeO
MeO
N
S
N
S
3bm
, 40 %
3bn
, 36 %
N
S
3au
3aw
, 78 %
, 75 %
3av
, N.D.
N
S
N
aReactions: 1a (1.5 eq., 0.56 mmol), 2 (0.37 mmol), 5.5 M TBHP solution in
decane (2.0 equiv, 0.74 mmol, 134 μL), NCS (30 mol%, 0.11 mmol), DMSO
(0.5 mL), 120 ℃, N2, 12 h.
5aa
, 22 %
4aa
4ab
, N.D.
, N.D.
aReactions: 1 (1.5 eq., 0.56 mmol), 2 (0.37 mmol), 5.5 M TBHP
solution in decane (2.0 equiv, 0.74 mmol,134 μL), NCS (30
mol%, 0.11 mmol), DMSO (0.5 mL), 120 ℃, N2, 12 h.
benzaldehydes including 2-fluorobenzaldehyde 2-chlorobenzald-
ehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde, 2-bromob-
enzaldehyde, 3-bromobenzaldehyde, 4-bromobenzaldehyde gave
the corresponding products in 34-88 % yield (Table 2, 3aj-3ap).
However, no desired product was detected when 2,4-dichloroben-
zaldehyde reacted with benzothiazole (Table 2, 3aq).
Furthermore, the reaction of 2-hydroxybenzaldehyde, 4-
(trifluoromethyl)benzaldehyde, 4-(tert-butoxyl)benzaldehyde and
2-nitrobenzaldehyde all resulted the products in good yields
(Table 2, 3ar-3au). However, the use of 3-nitrobenzaldehyde
also did not give any product (3av) the same as 2,5-
dimethoxybenzaldehyde (Table 2, 3ai), which compared to 2-
nitrobenzaldehyde (75%, Table 2, 3au) and 3,4-
dimethoxybenzaldehyde (44%, Table 2, 3ag) respectively
suggested that the position of the substituents on the
benzaldehyde affected the reaction yield significantly.
Surprisingly, benzaldehyde reacted with benzothiazole afforded
the acylated benzothiazole as the main product in 78 % yield
(Table 2, 3aw), which may go through an oxidative coupling
reaction between benzothiazole and aldehyde.25
Then, various substituted benzothiazoles and substituted
benzaldehydes were explored to check the tolerance of the
reaction (Table 3). Among them, most of the reactions gave the
target arylated products, however, 5-acetalbenzothiazole afforded
an acylated product under the optimized condition (Table 3, 3ba).
Benzothiazoles bearing a substituent (5-Cl, 6-NO2, 6-CN, 6-OMe)
afforded the expected arylated benzothiazoles in 12−94% yields
(Table 3, 3ba-3be). And it is known that C7 substitution on the
benzothiazole has a steric hindrance.26 Hence, it was not
surprising that no product was observer with 7-
methoxybenzothiazole (Table 3, 3bf). Unfortunately, the target
reaction also did not occur with 2-hydroxybenzaldehyde and 6-
nitrobenzothiazole (Table 3, 3bg), we envisioned that it might
because of the steric hindrance of the 2-hydroxybenzaldehyde.
Then, we tried the reactions of 3-hydroxybenzaldehyde or 4-
hydroxybenzaldehyde benzaldehydes with 6-nitrobenzothiazole
(Table 3, 3bh and 3bi). However, neither gave the target product,
which indicates that there is probably connection like hydrogen
bonds between the nitro group and hydroxyl group leading to
steric hindrance and hindering the reaction.27-29 Furthermore, 2-
bromobenzaldehyde and 2-methylbenzaldehyde reacted smoothly
with
6-nitrobenzothiazole
and
6-methoxybenzothiazole
generating the corresponding products in 19%-40% yields (Table
3, 3bj, 3bl, 3bm, 3bn). On the contrary, 4-bromobenzaldehyde
was not tolerated with 6-nitrobenzothiazole in the reaction
(Table 3, 3bk). Also, phenylacetaldehyde and crotonaldehyde
failed in the reaction under the current catalysts system as
reported (Table 3, 4aa and 4ab). In addition, quinoline
underwent the ortho-arylation with benzaldehyde to generate the
desired product in 22% yield (Table 3, 5aa).
Next, the generality of this method was investigated with
other substrates (Table 4). Notably, aliphatic aldehydes including
propionaldehyde and isobutyraldehyde gave acylation products in
22% and 45% yields (Table 4, 7aa and 7ab). But butyraldehyde
was not a suitable substrate that did not give any product (Table
4, 7ac).
Table 4. Acylation of benzothiazole with aliphatic aldehydes.
N
O
O
N
NCS, TBHP
H
R3
S
DMSO, 120 °C, N2
R3
S
1a
6
7
O
O
N
S
O
N
N
S
S
7aa
7ac, N.D.
, 22 %
7ab
, 45 %
aReactions: 1a (0.37 mmol), 6 (0.5 mL), 5.5 M TBHP
solution in decane (2.0 equiv, 0.74 mmol, 134 μL), NCS
(30 mol%, 0.11 mmol), DMSO (0.5 mL), 120 ℃, N2, 12 h.
In addition, a series of controlled experiments were
performed to explore the mechanism of this reaction as follows:
(A) An excess of a radical trapping agent 2,2,6,6-tetramethyl-1-
piperidinyloxy (TEMPO) was added into the mixture under the
optimal reaction conditions (Scheme 2A). The result showed that
the reaction was completely inhibited by TEMPO and a TEMPO-
trapped complex of a 2-methylbenzaldehyde radical (9b) was
detected by HRMS (see the ESI†), confirming the involvement of
a radical pathway. (B) The reaction between 2-aminothiophenol
(7a) and 2-methylbenzaldehyde (3b) under optimized reaction
conditions formed the target product (3ac) in 73% (Scheme 2B),

4
Tetrahedron Letter
Path A:
N
S
N
S
OH
NCS
3ac
, N.D.
O
tBuOOH
N
S
S
TEMPO (2 equiv.)
H
H
tBuO
O
1a
3b
NCS (30 mol%), TBHP (2 equiv.)
1
a
S
N
H
N
(A)
tBuO
H
O
N
DMSO, 120 °C, N2
tBuOH
O
O
S
9a
, N.D.
S
N
VIII
H
O
S
H
I
II
N
3b
H
N
O
H
S
N
9b,
by HRMS
detected
O
S
3aa
O
S
O
VII
N
N
H
3aa'
O
NCS (30 mol%)
TBHP (2 equiv.)
S
NH2
SH
III
O
N
S
H
(B)
(C)
3ac,
73%
N.D.
O
1/2
NH
2
DMSO, 120 °C, N2
VI
CO2
3b
7a
N
S
O
OH
OH
S
NH
H
O
IV
N
S
N
S
TBHP (2 equiv.)
S
tBuO
HO
Cl
3ac,
3ac,
O
DMSO, 120 °C, N2
V
tBuOOH
1a
1a
1a
8a
Path B:
NCS (30 mol%)
O
O
N
S
N
S
dry TBHP (2 equiv.)
(D)
(E)
H
H
H
70%
dry DMSO, 120 °C, N2
3b
3b
N
NH2
SH
tBuOOH
N
H
NCS (30 mol%)
TBHP (2 equiv.)
S
O
1a
N
S
SH
7b
N
S
7a
3ac,
3ac,
N.D.
72%
H2O, 120 °C, N2
3b
H
N
N
S
tBuO
OH
or
N
S
H
clear limewater
TBHP (2 equiv.)
O
N
S
S
(F)
H
3a
7c
DMSO, 120 °C, N2
CO2
3b
1a
Scheme 3. Plausible Mechanism
Scheme 2. Mechanistic Experiments.
a thio–ene radical process producing CO2 at the same time. 15d,17
Intermediate VI was highly reactive and would fast undergo an
intramolecular condensation process to afford VII, which can be
oxidized by H-atom transfer with a tert-butoxyl radical with the
help of DMSO to form the desired product 3aa;19c B) Direct
oxidative opening of the benzothiazole ring by TBHP.21 Then
oxidative condensation of the resultant 2-amino thiophenol with
the aldehyde with the help of a tert-butoxyl radical or a hydroxyl
radical.16
In summary, we have disclosed a procedure for direct
arylation of benzothiazoles with aryl aldehydes in DMSO, which
acts as a strong Lewis base probably could promote cleavage of
bonds through hydrogen bonds. The cheap organic catalyst NCS
is used as a radical initiated reagent and TBHP as an oxidant. The
reaction has a very broad substrate scope affording the arylated
products in 12–94% yields for 28 examples. Additionally,
acylated benzothiazoles are also produced from aryl aldehydes
and aliphatic aldehydes with 4 examples.
which was close to the reaction yield of benzothiazole with 2-
methylbenzaldehyde (72%, Table 2, 3ac). It indicated that the
transformation might proceed through
a
ring-opening
pathway.15a,d (C) 2-Methylbenzoylchloride (8a) was used as a
substrate instead of 2-methylbenzaldehyde to react with
benzothiazole in the absence of NCS (Scheme 2C). The
possibility of intermediate 2-methyl benzoyl chloride can be
ruled out since no product was observed in the reaction. (D)
TBHP in decane and DMSO were dried over anhydrous MgSO4
before adding into the mixture, and the arylated benzothiazole
was obtained in 70% (Scheme 2D). The result demonstrated that
H2O is useless in the reaction. (E) The reaction using H2O instead
of DMSO as the solvent did not result in the desired product,
which indicated that DMSO was very important to the reaction
(Scheme 2E). (F) The reaction of benzothiazole with 2-
methylbenzaldehyde was attempted connecting with clear
limewater (Scheme 2F). The clear limewater became cloudy
during the reaction, which indicated that CO2 was generated.
Based on the mechanistic experimental results and related
reports,30 the mechanism may be proposed with the key question
concerning the way of opening the benzothiazole. Two different
pathways may be envisioned as shown in Scheme 3: A) TBHP
forms a tert-butoxyl radical and a hydroxyl radical in the
presence of NCS.23 Then, a tert-butoxyl radical abstracts a H-
atom from the 4-methylbenzaldehyde 2a to form an acyl radical
I.31 On the other hand, DMSO coordinates C2-H of benzothiazole
1a to form an intermediate II,24 making the N atom further
electron-deficient. The acyl radical I is nucleophilic in nature and
attacks at the more electrophilic N of the intermediate II to form
the corresponding radical intermediate III. At the same time,
Acknowledgments
We are grateful for the financial support by the National
Natural Science Foundation of China (No.30900959) and the
Natural Science Foundation of Zhejiang Province.
(LY17C140003).
References and notes
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Graphical Abstract
NCS/TBHP promoted C2 Arylation of Benzothiazoles
with Aldehydes in DMSO
Leave this area blank for abstract info.
Wen-Xiu Xu, Fei-Xia Ye, Xing-Hai Liu, Jian-Quan Weng*
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, P. R. China
O
N
R1
R2
H
S
N
S
R2
R1
NCS, 70% TBHP
DMSO
28 examples
up to 94% yield
O
N
S
O
H
R3
R3
metal-free
4 examples
up to 78% yield
no strong oxidant
32 examples
DMSO promoted

6
Tetrahedron Letter
Highlights

Arylation and acylation of benzothiazole with
aldehydes.


Metal-free oxidative system.
Solvent as a strong Lewis base promotes the
reactions.