Facile synthesis of N-acyl 2-aminobenzothiazoles by NHC-catalyzed direct oxidative amidation of aldehydes

Article abstract of DOI:10.1039/c6cc08640c

A mild, general, and high yielding synthesis of N-acyl 2-aminobenzothiazoles has been demonstrated by N-heterocyclic carbene (NHC)-organocatalyzed direct amidation of aldehydes with 2-aminobenzothiazoles proceeding via acyl azolium intermediates. The carbene generated from the triazolium salt under oxidative conditions was the key for the success of this reaction. The method was subsequently applied to the synthesis of various biologically important N-acyl 2-aminobenzothiazoles.

Full text of DOI:10.1039/c6cc08640c

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Facile synthesis of N‐acyl 2‐aminobenzothiazoles by NHC‐
catalyzed direct oxidative amidation of aldehydes
Received 00th January 20xx,
Accepted 00th January 20xx
Sethulekshmi Premaletha,a Arghya Ghosh,a,b Sumi Joseph,a Santhivardhana Reddy Yetra,*,a,b and
Akkattu T. Biju*,a,b
DOI: 10.1039/x0xx00000x
www.rsc.org/
A
mild, general, and high yielding synthesis of N‐acyl 2‐ cases, the reaction needs a coupling reagent and a
aminobenzothiazoles has been demonstrated by the N‐ stoichiometric byproduct will be formed at the end of the
heterocyclic carbene (NHC)‐organocatalyzed direct amidation of reaction. In this context, we envisioned the N‐heterocyclic
aldehydes with 2‐aminobenzothiazoles proceeding via the acyl carbene (NHC)9,10 organocatalyzed direct oxidative amidation
azolium intermediates. The carbene generated from the triazolium of aldehydes with 2‐aminobenzothiazoles as a straightforward
salt under oxidative conditions was the key for the success of this route to access N‐acyl 2‐aminobenzothiazoles. Notably, NHC‐
reaction. The method was subsequently applied to the synthesis catalyzed redox‐amidation of ‐functionalized aldehydes with
of various biologically important N‐acyl 2‐aminobenzothiazoles.
amines has been independently reported by the Rovis11 and
Bode12 groups.13 In 2010, the Studer group uncovered the
oxidative amidation of aldehydes using hexafluoroisopropanol
(HFIP) as the acyl transfer agent.14 Very recently, the Brown
group disclosed the flow process for the NHC‐mediated anodic
oxidative amidation of aldehydes with amines.15 Herein, we
report the NHC‐catalyzed direct oxidative amidation of
aldehydes with 2‐aminobenzothiazoles.16,17 The reaction works
under mild conditions without the aid of coupling agent or acyl
transfer agent and the present method is extended to the
synthesis of several drug analogs.
Functionalized 2‐aminobenzothiazoles are an important
class of heterocyclic scaffolds due to the presence of these
motifs in numerous biologically active natural products and
several pharmaceuticals.1 For example, Riluzole (
A) is an
important drug belonging to this group, employed for the
treatment of amyotrophic lateral sclerosis (ALS), a lethal
neurodegenerative disease (Figure 1).2 Specifically, 2‐
aminobenzothiazoles substituted on the endocyclic nitrogen
are known to exhibit potential biological properties.3 Among
the functionalized N‐acyl 2‐aminobenzothiazoles, the 4‐
MeO
methoxy benzamide derivative of type
hydroxysteroid dehydrogenase type 1 inhibitors.4 Moreover,
the 4‐fluoro benzamide of type exhibits non‐xanthine based
A2B adenosine receptor antagonist activity,5 4‐nitro benzamide
derivative of the type
acts as raf‐1 inhibitor,6 and 4‐chloro
benzamide of type is known to be potent and selective
B acts as 17‐
OMe
O
N
O
N
OCF3
MeO
N
S
N
H
S
C
N
N
O
Et
S
H2N
H
Me
F
D
A
B
C
E
O
inhibitors of Candida albicans N‐myristoyltransferase.7 Since
this class of compounds exhibit wide range of biological
properties, developing simple and facile synthetic strategies
towards functionalized 2‐aminobenzothiazoles has attracted
much attention from organic chemists.
CF3
O
N
S
O
N
NH
N
H
S
N
H
O2N
Cl
HN
E
D
Figure 1. Biologically important 2‐aminobenzothiazole derivatives
Traditionally, the N‐acyl 2‐aminobenzothiazoles have been
synthesized by the reaction of 2‐aminobenzothiazoles with the
corresponding carboxylic acids/derivatives.8 However, in most
The present study commenced with the treatment of 4‐
chlorobenzaldehyhe 1a and 2‐aminobenzothiazole 2a with the
triazolium salt
4 in presence of oxidant 5 and Cs2CO3 as the
a Organic Chemistry Division, CSIR‐National Chemical Laboratory (CSIR‐NCL), Dr.
Homi Bhabha Road, Pune‐411008, India. E‐mail: * at.biju@ncl.res.in;
y.santhivardhna@ncl.res.in
base. Delightfully, under these conditions, a facile reaction
occurred leading to the formation of the expected N‐acyl 2‐
aminobenzothiazole 3a in 83% yield ( Table 1, entry 1). As
anticipated, the reaction did not work at all in the absence of
cAcademy of Scientific and Innovative Research (AcSIR), New Delhi 110020, India
Electronic Supplementary Information (ESI) available: Details on experimental
procedure, characterization data of all compounds See
DOI: 10.1039/x0xx00000x
the triazolium salt
4
(entry 2). The performed reactions using
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common NHCs derived from precursors
yield of 3a (entries 3‐5), whereas, NHC derived from
6
‐
8
returned reduced Additionally, substitution at the meta‐position as well as ortho‐
position of aryl ring of resulted in the smooth conversion to
furnished 3a in comparable yield (entry 6). The reaction the desired product in good yield (3f 3h). Furthermore,
resulted in similar outcome when performed in DBU instead of polycyclic aromatic aldehydes such as naphthyl and pyrene
Cs2CO3 (entry 7), whereas the other bases, such as DMAP, KOt‐ carboxaldehydes afforded the desired product (3i 3j) in good
9
1
‐
,
Bu and, K2CO3 furnished inferior results (entries 8‐10). A quick yields. Moreover, interesting aldehydes such as ferrocene
solvent screening revealed that, solvents such as DME, 1,4‐ carboxaldehyde and thiophene 2‐carboxaldehyde also
dioxane and toluene gave reduced yields (entries 11‐13). furnished the corresponding products in good yields, further
Interestingly, the use of CH2Cl2 improved the yield of 3a to 93% expanding the scope of this direct amidation reaction (3k
(entry 14). Moreover, decreasing the amount of the carbene Notably, ,β‐unsaturated aldehydes with aromatic as well as
precursor resulted in reduced yield of the product (entry 15). aliphatic groups at the ‐position underwent smooth
Thus, the use of triazolium salt (20 mol %) and Cs2CO3 as amidation reaction to form the products in moderate to good
base (1.2 equiv) in CH2Cl2 at 25 °C with as the oxidant was yields (3m, 3n). Interestingly, citral can also be used as a
, 3l).

4

4
5
found to be the optimal conditions for this reaction (entry 14).
coupling partner and the corresponding amide (3o) was
isolated in 80% yield, demonstrating the versatility of this
reaction.
Table 1. Optimization of the reaction conditionsa
yield of
entry
variation of the standard conditions
3a (%)b
83
1
2
none
without 4
<5
60
3
6 instead of 4
4
7 instead of 4
35
5
8 instead of 4
54
6
9 instead of 4
80
7
DBU instead of Cs2CO3
DMAP instead of Cs2CO3
K2CO3 instead of Cs2CO3
KOt-Bu instead of Cs2CO3
DME instead of THF
1,4-dioxane instead of THF
toluene instead of THF
CH2Cl2 instead of THF
10 mol % 4 instead of 20 mol %
78
8
20
9
58
10
11
12
13
14
15
35
66
78
44
Scheme 1. Substrate Scope for the Direct Amidation of Aldehydes: Variation of
Aldehydes. Reaction conditions: 1 (1.0 mmol), 2a (0.5 mmol), 4 (20 mol %), 5 (2.0
equiv), Cs2CO3 (1.2 equiv), CH2Cl2 (4.0 mL), 25 °C and 12 h. Given are yields of
isolated products after silica gel flash column chromatography.
93
71
a Standard conditions: 1a (0.50 mmol), 2a (0.25 mmol), 4 (20 mol %), Cs2CO3 (1.2
equiv), 5 (2.0 equiv), THF (2.0 mL), 25 °C and 12 h. b Isolated yield after column
chromatography.
Next, we focused our attention on the variation of 2‐
aminobenzothiazoles (Scheme 2). 2‐aminobenzothiazoles with
electron‐donating and ‐withdrawing groups at 6‐position of
aryl ring underwent efficient amidation reaction with 4‐
chlorobenzaldehyde to afford the desired benzamide products
(
3p‐3t) in good yields. Moreover, difluoro substitution in aryl
ring of benzothiazole furnished the amide 3u in 75% yield.
Interestingly, 2‐amino thiazole can also be used as coupling
partner, and the target product 3v was formed in 42% yield.
With the optimized reaction conditions, we evaluated the
substrate scope of this NHC‐catalyzed amidation reaction.
First, tolerance of this reaction with various aldehydes has
been tested (Scheme 1). Aldehydes bearing electron‐donating
and ‐withdrawing groups at the para‐position of the aryl ring
were well tolerated, resulting in the synthesis of N‐acyl 2‐
aminobenzothiazoles in high yields of >80% in all cases (3a‐3e).
2 | J. Name., 2012, 00, 1‐3
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performed under optimized conditions in the absence of
5
using 2‐bromoenal 10, the unsaturated benzamide 3z was
formed in 65% yield (Scheme 4, eq 1). This indicates the
intermediacy of NHC‐bound acyl azolium 11 in the present
reaction. Moreover, mixing 1a with 2a in the absence of NHC
precatalyst
4 did not afford the amide product 3a as well as
the imine 12, and the unreacted 1a and 2a were quantitatively
recovered (eq 2). It may be mentioned that the absence of
imine formation rules out the amide formation directly from
imines under oxidative conditions.23,24
Scheme 2. Variation of 2‐Aminobenzothiazoles. Reaction conditions: 1a (1.0
mmol), 2 (0.5 mmol), 4 (20 mol %), 5 (2.0 equiv), Cs2CO3 (1.2 equiv), CH2Cl2 (4.0
mL), 25 °C and 12 h. Given are yields of isoalted products after silica gel flash
column chromatography.
Then, we turned our attention on application of the
present method for the synthesis of various biologically active
N‐acyl 2‐aminobenzothiazoles (Scheme 3). The direct
amidation of benzaldehyde with 2‐aminobenzothiazole under
optimized reaction conditions afforded benzamide 3w in 74%
yield. The compound 3w is known to exhibit anti‐infective and
herbicidal activity.3 The reaction of 4‐toluadehyde with 2a
furnished the benzamide 3x in 67% yield, and 3x is known to
act as inhibitors of protein‐protein interaction between KRS
and a laminin receptor.18 The benzamide 3y, derived from 3,4‐
dichlobenzaldehyde and 2a in 93% yield is known to bind to
the nuclear hormone receptors.19 The ‐unsaturated amide
3z was synthesized from cinnamaldehyde and 2a in 70% yield
and 3z possesses antioxidant and anticonvulsant activity.20
Moreover, the reaction of 4‐chloro benzaldehyde and 6‐nitro
2‐aminobenzothiazole afforded the antitubercular agent 3aa in
78% yield.21 Finally, the benzamide 3ab was synthesized from
4‐chlorobenzaldehyde and 6‐methoxy 2‐amino benzothiazole
in 61% yield, and is useful in targeted cancer therapy.22
Scheme 4. Mechanistic Experiments
The tentative mechanism of this NHC‐catalyzed amidation
reaction is shown in Scheme 5. The NHC generated from
under basic conditions undergoes nucleophilic attack on the
aldehyde followed by a proton transfer generating the
nucleophilic Breslow intermediate I 25
In the presence of
4
1
.
5, I
undergoes oxidation to generate II, which is the key acyl‐
azolium intermediate. Nucleophilic 1,2 addition of the amine
2a on to intermediate II will form the aminal intermediate III
The intermediate III, upon regeneration of carbene affords the
desired amide
.
3
.
nucleophilic attack,
proton transfer
O
N
R
S
N
N
N
R
HN
Ph
O
H
1
3
base
N
BF4
Ph
Ph
N
N
OH
R
H
N
N
Ph
4
O
N
Breslow
intermediate
N
R
N
S
N
I
N
HN
III
1,2-addition
acyl azolium
5
S
H2N
Ph
O
N
N
N
R
2a
N
II
Scheme 3. Synthesis of biologically active N‐Acyl 2‐Aminobenzothiazoles.
Reaction conditions: 1 (1.0 mmol), 2 (0.5 mmol), 4 (20 mol %), 5 (2.0 equiv),
Cs2CO3 (1.2 equiv), CH2Cl2 (4.0 mL), 25 °C and 12 h. b Isolated yields are given.
Scheme 5. Proposed Mechanism of the Reaction
In conclusion, we have demonstrated the NHC‐catalyzed
oxidative amidation route for the synthesis of N‐acyl 2‐
To get insight into the mechanism of this reaction, we have
carried out mechanistic experiments. When the reaction was
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Angew. Chem., Int. Ed., 2012, 51, 11686; (k) D. T. Cohen and
K. A.Scheidt, Chem. Sci., 2012, , 53; (l) A. T. Biju, N. Kuhl and
F. Glorius, Acc. Chem. Res., 2011, 44, 1182; (m) V. Nair, R. S.
Menon, A. T. Biju, C. R. Sinu, R. R. Paul, A. Jose and V.
Sreekumar, Chem. Soc. Rev., 2011, 40, 5336; (n) D. Enders, O.
Niemeier and A. Henseler, Chem. Rev., 2007, 107, 5606.
aminobenzothiazoles. The reaction proceeds via the
generation of the NHC‐bound acyl azolium intermediates. Mild
reaction conditions without the aid of a coupling/acyl transfer
agent, good functional group compatibility, high yields of
products, convenient synthesis of drug analogs are the notable
features of the present reaction.
Generous financial support from Board of Research in
Nuclear Sciences (BRNS), Government of India (Grant
No.37(2)/14/49/2014‐BRNS/) has been kindly acknowledged.
A. G. and S. R. Y thank CSIR, New Delhi for the research
fellowships. We thank Dr. P. R. Rajamohanan for the excellent
NMR support, Dr. B. Santhakumari for the HRMS data.
3
10 For reviews on oxidative NHC‐catalysis, see: (a) S. De Sarkar,
A. Biswas, R. C. Samanta and A. Studer, Chem. Eur. J., 2013,
19, 4664; (b) H. U. Vora, P. Wheeler and T. Rovis, Adv. Synth.
Catal., 2012, 354, 1617; (c) C. E. I. Knappke, A. Imami and A.
Jacobi von Wangelin, ChemCatChem., 2012, 4, 937.
11 H. U. Vora and T. Rovis, J. Am. Chem. Soc., 2007, 129, 13796.
12 J. W. Bode and S. S. Sohn, J. Am. Chem. Soc., 2007, 129,
13798.
13 For the NHC‐catalyzed amidation of unactivated esters with
amino alcohols, see: M. Movassaghi and M. A. Schmidt, Org.
Lett., 2005, 7, 2453.
Notes and references
14 (a) S. De Sarkar and A. Studer, Org. Lett., 2010, 12, 1992; See
also: (b) S. De Sarkar, S. Grimme and A. Studer, J. Am. Chem.
Soc., 2010, 132, 1190; (c) R. C. Samanta, S. De Sarkar, R.
1
(a) R. Chikhale, S. Menghani, R. Babu, R. Bansode, G.
Bhargavi, N. Karodia, M. V. Rajasekharan, A. Paradkar and P.
Khedekar, Eur. J. Med. Chem., 2015, 96, 30; (b) V. Namani, B.
B. K. Goud, Y. B. Kumari, R. Kumbham, K. Balakrishna and B.
Bhima, Asian J. Chem., 2015, 27, 4575; (c) H. Y. Cho, A. U.
Mushtaq, J. Y. Lee, D. G. Kim, M. S. Seok, M. Jang, B. W. Han,
S. Kim and Y. H. Jeon, FEBS Lett., 2014, 588, 2851.
(a) P. Jimonet, F. Audiau, M. Barreau, J.‐C. Blanchard, A.
Boireau, Y. Bour, M.‐A. Cole´no, A. Doble, G. Doerflinger, C.
D. Huu, M.‐H. Donat, J. M. Duchesne, P. Ganil, C. Gue´re´my,
E. Honore´, B. Just, R. Kerphirique, S. Gontier, P. Hubert, P.
M. Laduron, J. L. Blevec, M. Meunier, J.‐M. Miquet, C.
Nemecek, M. Pasquet, O. Piot, J. Pratt, J. Rataud, M.
Reibaud, J.‐M. Stutzmann and S. Mignani, J. Med. Chem.
1999, 42, 2828; (b) A. Doble, Neurology, 1996, 47. S233.
D. Fajkusova, M. Pesko, S. Keltosova, J. Guo, Z. Oktabec, M.
Vejsova, P. Kollar, A. Coffey, J. Csollei, K. Kralova and
Jampilek, Bioorg. Med. Chem., 2012, 20, 7059.
R. Hartmann, M. Frotscher, S. Marchais‐Oberwinkler, A.
Oster, and A. Spadaro, PCT Int. Appl., WO 2012025638, Mar
1, 2012.
A. W.‐H. Cheung, J. Brinkman, F. Firooznia, A. Flohr, J.
Grimsby, M. L. Gubler, K. Guertin, R. Hamid, N. Marcopulos,
R. D. Norcross, L. Qi, G. Ramsey, K. J. Tan, Y. Wen and R.
Sarabu, Bioorg. Med. Chem. Lett., 2010, 20, 4140.
E. Y. Song, N. Kaur, M.‐Y. Park, Y. Jin, K. Lee, G. Kim, K. Y.
Lee, J. S. Yang, J. H. Shin, K.‐Y. Nam, K. T. No and G. Han, Eur.
J. Med. Chem., 2008, 43, 1519.
Frӧhlich, S. Grimme and A. Studer, Chem. Sci., 2013, 4, 2177;
(d) D. L. Cramer, S. Bera, and A. Studer, Chem. Eur. J., 2016,
22, 7403.
15 R. A. Green, D. Pletcher, S. G. Leach and R. C. D. Brown, Org.
Lett., 2016, 18, 1198. A stoichiometric amounts of NHC was
used in this method.
2
16 For the NHC‐catalyzed oxidative amidation of aldehydes
proceeding via the acyl anion equivalents, see: A. Alanthadka
and C. U. Maheswari, Adv. Synth. Catal., 2015, 357, 1199.
17 For the NHC‐catalyzed kinetic resolution of sulfoximines
using oxidative amidation, see: S. Dong, M. Frings, H. Cheng,
J. Wen, D. Zhang, G. Raabe and C. Bolm, J. Am. Chem. Soc.,
2016, 138, 2166; For related racemic report see: (b) A. Porey,
S. Santra and J. Guin, Asian. J. Org. Chem., 2016, 5, 870.
3
4
5
18 (a) K. Waisser, J. Kuneš and Ž. Odlerová, Collect. Czech.
Chem. Commun., 1991, 56, 2978; (b) Y. Hur, D.‐H. Kim, E.‐K.
Kim, J.‐H. Park, J.‐E. Joo, H.‐W. Kang, S.‐W. Oh, D.‐K. Kim and
K.‐K. Ahn, PCT Int. Appl., 2013043001, Mar 28, 2013.
19 S. Kerwin, L. H. Hurley, M. R. DeLuca and B. M. Moore, III.
PCT Int. Appl., 9748694, Dec 24, 1997.
20 (a) N. D. Amnerkar, and K. P. Bhusari, Eur. J. Med. Chem.,
2010, 45, 149; (b) S. Durgamma, P. R. Reddy, V. Padmavathi
and A. Padmaja, J. Het. Chem., 2016, 53, 738.
21 A. Kamal, R. V. C. R. N. C. Shetti, P. Swapna, S. Azeeza, A. M.
Reddy, I. A. Khan, S. T. Abdullah, S. Sharma and N. P. Kalia,
Indian Pat. Appl., 2010DE02179, Mar 16, 2012.
22 J. M. Ready, D. Nijhawan, S. S. Gonzales, and P.
Theodoropoulos, PCT Int. Appl., 2015035051, Mar 12, 2015.
23 E. S. Devi, A. Alanthadka, A. Tamilselvi, S. Nagarajan, V.
Sridharana and C. U. Maheswari, Org. Biomol. Chem., 2016,
14, 8228.
24 Competition experiments carried out between 2‐
aminobenzothiazole and benzyl alcohol with 4‐
chlorobenzaldehyde under the present reaction conditions
revealed that the benzyl alcohol reacted ~2 times faster
(leading to the formation of the corresponding benzyl ester)
6
7
8
K. Yamazaki, Y. Kaneko, K. Suwa, S. Ebara, K. Nakazawa and
K. Yasuno, Bioorg. Med. Chem., 2005, 13, 2509.
For selected reviews, see: (a) R. M. de Figueiredo, J.‐S. Suppo
and J.‐M. Campagne, Chem. Rev., 2016, 116, DOI:
10.1021/acs.chem rev.6b00237; (b) V. Pattabiraman and J.
W. Bode, Nature, 2011, 480, 471; (c) E. Valeur and M.
Bradley, Chem. Soc. Rev., 2009, 38, 606; (d) C. A. G. N.
Montalbetti and V. Falque, Tetrahedron, 2005, 61, 10827; (e)
S.‐Y. Han and Y.‐A. Kim, Tetrahedron, 2004, 60, 2447.
For recent reviews on NHC catalysis, see: (a) M. H. Wang and
9
compared
aminobenzothiazole.
25 R. Breslow, J. Am. Chem. Soc., 1958, 80, 3719.
to
amidation
reaction
using
2‐
K. A. Scheidt, Angew. Chem., Int. Ed., 2016, 55, 14912; (b) D.
M. Flanigan, F. Romanov‐Michailidis, N. A. White and T.
Rovis, Chem. Rev., 2015, 115, 9307; (c) R. S. Menon, A. T. Biju
and V. Nair, Chem. Soc. Rev., 2015, 44, 5040; (d) S. R. Yetra,
A. Patra and A. T. Biju, Synthesis, 2015, 47, 1357; (e) M. N.
Hopkinson, C. Richter, M. Schedler and F. Glorius, Nature,
2014, 510, 485; (f) J. Mahatthananchai and J. W. Bode, Acc.
Chem. Res., 2014, 47, 696; (g) S. J. Ryan, L. Candish and D. W.
Lupton, Chem. Soc. Rev., 2013, 42, 4906; (h) A. Grossmann
and D. Enders, Angew. Chem., Int. Ed., 2012, 51, 314; (i) X.
Bugaut and F. Glorius, Chem. Soc. Rev., 2012, 41, 351; (j) J.
Izquierdo, G. E. Hutson, D. T. Cohen and K. A. Scheidt,
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