Utility of N -Bromosuccinimide-Water Combination as a Green Reagent for Synthesis of N,S-Heterocycles and Dithiocarbamates from Styrenes

Article abstract of DOI:10.1055/s-0040-1707258

An efficient and unprecedented green protocol has been developed for the synthesis of N,S-heterocycles from styrenes and alkyl dithiocarbamates with high to excellent yields. The reaction of primary or secondary amines, CS ₂, and styrenes was carried out in water in the presence of a catalytic amount of an inorganic base. All products were made by using an N -bromosuccinimide-H ₂O combination as a green and inexpensive reagent.

Full text of DOI:10.1055/s-0040-1707258

SYNLETT0936-52141437-2096
Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart
2020, 31, A–E
letter
A
en
F. Matloubi Moghaddam, M. Goudarzi
Letter
Synlett
Utility of N-Bromosuccinimide–Water Combination as a Green
Reagent for Synthesis of N,S-Heterocycles and Dithiocarbamates
from Styrenes
Firouz Matloubi Moghaddam* 0241-98
S
R2
Mehri Goudarzi
S
NH2
S
no additive
12 examples
S
R2
N
Laboratory of Organic Synthesis and Natural Products,
Department of Chemistry, Sharif University of Technology,
Azadi Street, P.O. Box 111559516, Tehran, Iran
matloubi@sharif.edu
80 °C, 3 h
route A
R1
R3
N
HO
S
CS2 + R3NH2
NBS, rt, 12 h, H2O
9 examples
S
K2CO3, 0–5 °C, 5 h
route B
R1
R1
Corresponding Author
FLe.aMMbaoairltamltoouartbyliooMufboOig@rhgsaahndaidrciafSm.eydnuthesis and Natural Products, Department of Chemistry, Sharif University of Technology, Azadi Street, P.O. Box 111559516, Tehran, Iran
O
R4
CS2 + R42NH
S
N
9 examples
R4
K2CO3, 0–5 °C, 5 h
route C
S
R1
Received: 22.05.2020
Accepted after revision: 10.07.2020
Published online: 28.08.2020
agriculture, rubber manufacturing, RAFT polymerizations,
and medicinal chemistry.7 Moreover, dithiocarbamic acids
can be easily prepared in situ from carbon disulfide and
primary or secondary amines, and they can act as efficient
binucleophiles or nucleophiles, respectively. Recently, vari-
ous N,S-heterocycles have been prepared from dithiocarba-
mic acids.8
N-Bromosuccinimide (NBS) is one of the most import-
ant nontoxic sources of cationic and radical bromine. It is
widely used in various reactions for the bromination of
such chemical compounds as 1,3-diketones,9 chalones,10
unsymmetrical indodicarbocyanine dyes,11 and ethynyl-
benzene.12
DOI: 10.1055/s-0040-1707258; Art ID: st-2020-b0304-l
Abstract An efficient and unprecedented green protocol has been
developed for the synthesis of N,S-heterocycles from styrenes and alkyl
dithiocarbamates with high to excellent yields. The reaction of primary
or secondary amines, CS2, and styrenes was carried out in water in the
presence of a catalytic amount of an inorganic base. All products were
made by using an N-bromosuccinimide–H2O combination as a green
and inexpensive reagent.
Key words dithiocarbamates, styrenes, green chemistry, thiazoles,
bromosuccinimide
In this letter, we report a difunctionalization of com-
mercially available styrenes for the synthesis of dithiocar-
bamates or N,S-heterocycles in water as solvent and a
source of oxygen. Furthermore, NBS plays a dual role, acting
as an oxidant and a safe source of bromine (Scheme 1;
routes A–C).
Due to their interesting properties and applications in
unique syntheses of chemical compounds, styrenes have at-
tracted considerable attention from synthetic chemists in
recent years. Although these versatile small molecules are
chemically quite reactive and can polymerize rapidly, sty-
renes can be used directly in syntheses of important classes
of heterocycles and -X-acetophenones (X = C, N, O, S, Br).1
For example, Zhang and co-workers reported a copper-cat-
alyzed aerobic difunctionalization of styrenes with cyclic
ethers for the synthesis of the oxyalkylated products.2 Su-
dalai and co-workers developed an I2-catalyzed regioselec-
tive oxo- and hydroxyacyloxylation of alkenes with carbox-
ylic acids under mild conditions.3 Recently, the same group
developed an efficient method for the synthesis of regiose-
lective oxoamination of styrenes by an NBS–DMSO system
and secondary amines.4 More recently, the Yang group re-
ported difunctionalization of alkenes by a one-pot four-
component reaction of two alkenes, an aromatic or aliphat-
ic aldehyde, and tert-butyl hydroperoxide.5
S
R2
NH2
S
S
no additive
S
R2
N
80 °C, 3 h
route A
R1
R3
N
HO
S
CS2 + R3NH2
NBS, rt, 12 h, H2O
S
K2CO3, 0–5 °C, 5 h
R1
route B
R1
O
R4
CS2 + R42NH
S
N
R4
K2CO3, 0–5 °C, 5 h
route C
S
R1
Scheme 1 Synthesis of N,S-heterocycles and dithiocarbamates by us-
ing an NBS–H2O combination
Dithiocarbamates are valuable compounds due to their
wide utility in syntheses of small organic molecules and bi-
ologically active compounds.6 They are also widely used in
© 2020. Thieme. All rights reserved. Synlett 2020, 31, A–E
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
F. Matloubi Moghaddam, M. Goudarzi
Letter
Synlett
Initially, we investigated the one-pot reaction of an alkyl
dithiocarbamate with a styrene for the synthesis of a 2-(al-
kylsulfanyl)-4-phenyl-1,3-thiazole. We observed that treat-
ment of one equivalent of styrene (1a) with two equiva-
lents of NBS in H2O at room temperature for 12 hours, fol-
lowed by the addition of one equivalent of benzyl
dithiocarbamate (2a) and further heating at 80 °C for three
hours, gave 2-(benzylsulfanyl)-4-phenyl-1,3-thiazole (3a)
in 86% isolated yield. Changing the solvent system from wa-
ter to a water–organic solvent mixture provided an unsatis-
factory yield of 3a. A further increase in the amount of the
dithiocarbamate 2a did not improve the yield. Whereas the
replacement of NBS by NIS afforded 3a in 28% yield, 3a was
not formed with NCS.
S
NBS, rt, 12 h, H2O
S
S
N
, 80 °C, 3 h
Cl
NH2
S
1a
3b (75%)a
2b
Cl
Scheme 2 Synthesis of thiazole 3b on a 5 mmol scale
Inspired by this green and simple approach for the syn-
thesis of 2-(alkylsulfanyl)-4-phenyl-1,3-thiazoles, we ex-
panded the utility of this protocol by using primary amines.
To study this reaction, styrene (1a; 1 mmol) was treated
with NBS (2 mmol) at 25 °C in water for 12 hours to give -
bromoacetophenone (4a); subsequent addition of mixture
of benzylamine and carbon disulfide gave the desired prod-
uct 6a in a trace amount (Table 2, entry 1). As expected, the
addition of an inorganic or organic base was effective in
giving 6a in yields of 14–45% (entries 2–5). The yield was
not improved by performing the reaction in refluxing H2O
(entry 6), but on changing the temperature from 25 °C to 0
°C, an increase in the yield of 6a was observed (entry 7). In
addition, neither lowering nor increasing the catalyst con-
centration significantly improved the yield (entries 8–10).
Finally, a higher yield (76%) of 6a was obtained by increas-
ing the amount of 5a to 1.5 equivalents (entry 11).
With the optimized reaction conditions in hand,13 we
examined the scope of the reaction of various styrenes 1a–
e with alkyl dithiocarbamates 2a–c (Table 1).
Table 1 Diversity in the Synthesis of 2-(Alkylsulfanyl)-4-phenyl-1,3-
thiazolesa
S
NBS, rt, 12 h, H2O
R2
S
S
N
, 80 °C, 3 h
R2
R1
R1
1a–e
S
NH2
2a–c
3a–l
Various primary amines and styrenes were then exam-
ined under the optimized reaction conditions (Scheme 3).14
Moderate to high yields (37–81%) of racemic products were
Entry
R1
R2
Product Yieldb (%)
1
2
1a
1a
1b
1b
1c
1c
1c
1d
1d
1e
1e
1e
H
2a
Bn
3a
3b
3c
3d
3e
3f
86
91
83
87
91
93
73
84
87
74
79
68
H
2b
2a
2b
2a
2b
2c
2a
2b
2a
2b
2c
4-chlorobenzyl
Table 2 Optimization of the Reaction of Benzylamine (5a) with
Styrene (1a)a
3
4-Me
4-Me
Bn
4
4-chlorobenzyl
5
4-MeO
4-MeO
4-MeO
3-O2N
3-O2N
4-Br
Bn
NH2
+ CS2
O
6
4-chlorobenzyl
HO
N
Br
S
NBS, rt, 12 h, H2O
5a
7
Pr
3g
3h
3i
S
conditions
8
Bn
4a
1a
6a
9
4-chlorobenzyl
10
11
12
Bn
3j
Entry
Base (equiv)
Temp
Yielda (%)
4-Br
4-chlorobenzyl
Pr
3k
3l
1
2
–
rt
trace
38
32
45
14
22
68
68
66
63
76
4-Br
NaOH (1)
KOH (1)
K2CO3 (1)
DABCO (1)
K2CO3 (1)
K2CO3 (1)
rt
a Reaction conditions: styrene 1 (1 mmol), NBS (2 mmol), H2O (2 mL), rt, 12 h,
then dithiocarbamate 2 (1 mmol), 80 °C, 3 h.
b Isolated yield.
3
rt
4
rt
5
rt
The structures of products 3a–l were confirmed by 13C
NMR spectroscopy. The C-2 peak of the thiazole ring ap-
peared at  = 163 ppm, and the peaks for the C-4 and C-5
atoms of the thiazole ring appeared at  = 154 and 136 ppm,
respectively.
To demonstrate the synthetic utility of this reaction, we
performed it at a 5 mmol scale and obtained product 3b in
75% yield (Scheme 2).
6
reflux
0 °C
0 °C
0 °C
0 °C
0 °C
7
8
K2CO3 (0.5)
K2CO3 (0.25)
K2CO3 (1.5)
9
10
11b
K2CO3 (0.25)
a Isolated yield
b 5a (1.5 equiv).
© 2020. Thieme. All rights reserved. Synlett 2020, 31, A–E

C
F. Matloubi Moghaddam, M. Goudarzi
Letter
Synlett
obtained. Higher yields were obtained by using benzyl-
amine and styrenes containing an electron-withdrawing
group on the phenyl ring.
ithiocarbamic acids derived from secondary amines
then were selected as nucleophilic partners for this proto-
col.15 2-Oxo-2-phenylethyl diethylcarbamate (7a) was syn-
thesized in a satisfactory yield by a one-pot reaction of di-
ethylamine, CS2, and styrene with an NBS–H2O combination
for five hours (Scheme 4). The scope of this reaction was ex-
tended by using various secondary amines and styrenes.
The corresponding products 7a–i were obtained in moder-
ate to high yields.
Finally, gram-scale reactions were performed to demon-
strate the industrial application of the method in the syn-
theses of 3-benzyl-4-hydroxy-4-phenyl-1,3-thiazolidine-2-
thione (6a) and 2-oxo-2-phenylethyl diethylcarbamate (7a)
on 5 mmol scale, and the desired products were obtained in
yields of 63 and 68%, respectively.
R2
HO
N
S
NBS, rt, 12 h, H2O
S
then (CS2 + R2NH2),
R
K2CO3, 0–5 °C, 5 h
R
1
6a–i
S
S
S
S
S
S
N
N
S
N
OH
N
S
HO
OH
OH
6a (76%)a
6d (56%)
6b (68%)
6c (48%)
Based on previous studies,16 a plausible mechanism for
the formation of the various products is proposed (Scheme
5). Initially, NBS reacts with styrene (1a) to form the bro-
monium ion A. Bromohydrin B is then formed by regio-
S
S
S
N
S
N
N
HO
N
HO
S
HO
HO
S
S
S
Br
6g (63%)
NO2
6h (81%)
Br
Br
O
6f (74%)
6e (50%)
Br
N
S
H2O
N
O
HO
S
Br
A
OH
6i (37%)
B
O
Scheme 3 Synthesis of 1,3-thiazolidine-2-thiones. Reagents and condi-
tions: styrene 1 (1 mmol), NBS (2 mmol), H2O (2 mL), rt, 12 h, then amine
5 (1.5 equiv), CS2 (3 equiv), K2CO3 (0.25 equiv), 0 to 5 °C, 5 h. a Isolated
yield.
1a
Br
N
H
O
Br
Br
O
C
R2
O
NBS, rt, 12 h, H2O
S
N
R2
then (CS2 + R22NH),
K2CO3, 0–5 °C, 5 h
R3
S
R3
R1
O
R1
N
O
R1
1
7a–i
Br
S
S
HN
S
S
R1
S
O
O
NHR23 + CS2
H2N
S
O
O
O
O
S
S
N
S
N
N
N
N
E
D
S
S
S
7
7a (83%)a
7b (57%)
7c (69%)
R2NH2 + CS2
H2O
O
O
R1
S
O
S
S
N
S
S
R2
N
S
N
H
O
S
S
S
S
NO2
NO2
7d (63%)
7e (91%)
7f (76%)
3
O
S
O
S
O
N
N
S
N
F
S
S
S
Br
Br
NO2
S
R2
7g (61%)
7h (72%)
7i (71%)
N
S
Scheme 4 Synthesis of 2-aryl-2-oxoethyl carbamates. Reagents and
OH
conditions: styrene 1 (1 mmol), NBS (2 mmol), H2O (2 mL), rt, 12 h, then
amine (1.5 equiv), CS2 (3 equiv), K2CO3 (0.25 equiv), 0 to 5 °C, 5 h. a
Isolated yield.
6
Scheme 5 Proposed mechanism
© 2020. Thieme. All rights reserved. Synlett 2020, 31, A–E

D
F. Matloubi Moghaddam, M. Goudarzi
Letter
Synlett
selective addition of H2O. The hypobromite intermediate C,
produced by the reaction of the bromohydrin B with NBS,
then undergoes cleavage to form phenacyl bromide (D). Fi-
nally, phenacyl bromide (D) reacts with an alkyl dithiocar-
bamate or a dithiocarbamic acid derived from a primary or
a secondary amine to give the desired products 3, 6, and 7,
respectively.
In conclusion, we have demonstrated the synthesis of
dithiocarbamates and two types of N,S-heterocycle through
the reaction of styrenes with dithiocarbamic acids or alkyl
dithiocarbamates. More importantly, the NBS–H2O combi-
nation is a green and inexpensive reagent for converting
styrenes into the corresponding phenacyl bromides in a
single step. The reactions are characterized by the use of
mild and effective reaction conditions, short reaction times,
and moderate to excellent product yields.
(8) (a) Shaabani, A.; Hooshmand, S. E. Ultrason. Sonochem. 2018, 40,
84. (b) Gabillet, S.; Lecerclé, D.; Loreau, O.; Carboni, M.; Dézard,
S.; Gomis, J.-M.; Taran, F. Org. Lett. 2007, 9, 3925. (c) Hajibabaei,
K.; Zali-Boeini, H. Synlett 2015, 26, 108.
(9) Zou, L.-H.; Li, Y.-C.; Li, P.-G.; Zhou, J.; Wu, Z. Eur. J. Org. Chem.
2018, 2018, 5639.
(10) (a) Wang, Z.; Lin, L.; Zhou, P.; Liu, X.; Feng, X. Chem. Commun.
2017, 53, 3462. (b) Li, W.; Zhou, P.; Li, G.; Lin, L.; Feng, X. Adv.
Synth. Catal. 2020, 362, 1982. (c) Cai, Y.; Liu, X.; Hui, Y.; Jiang, J.;
Wang, W.; Chen, W.; Lin, L.; Feng, X. Angew. Chem. Int. Ed. 2010,
49, 6160.
(11) Miltsov, S.; Goikhman, M.; Yakimansky, A.; Misharev, A.; Puyol,
M.; Alonso, J. Tetrahedron Lett. 2019, 60, 151005.
(12) Gao, Y.; Wu, W.; Huang, Y.; Huang, K.; Jiang, H. Org. Chem. Front.
2014, 1, 361.
(13) 2-(Alkylsulfanyl)-4-aryl-1,3-thiazoles 3a–l; General Proce-
dure
NBS (2.0 mmol) was added to a solution of the appropriate
styrene 1 (1.0 mmol) in H2O (2 mL), and the mixture was stirred
for 12 h. The appropriate alkyl dithiocarbamate 2 (1.0 mmol)
was added, and the mixture was stirred at 80 °C for 3 h. The
resulting mixture was cooled to rt and extracted with EtOAc
(3 × 5 mL). The combined organic phase was dried (Na2SO4), fil-
tered, and concentrated in vacuo. The residue was purified by
chromatography [silica gel, hexane–EtOAc (9:1)].
Acknowledgment
We are grateful to the faculty of chemistry of the Sharif University of
Technology for supporting this work.
2-(Benzylsulfanyl)-4-phenyl-1,3-thiazole (3a)
Supporting Information
White crystalline solid; yield: 243 mg (86%); mp 58–60 °C.
IR (KBr): 3102, 3065, 2918, 1953, 1888, 1590, 1443, 1039 cm–1
.
1H NMR (500 MHz, CDCl3):  = 4.56 (s, 2 H), 7.30–7.41 (m, 5 H),
7.46–7.50 (m, 4 H), 7.97 (d, J = 8.0, Hz, 2 H). 13C NMR (100 MHz,
CDCl3):  = 38.8, 112.8, 126.3, 127.7, 128.2, 128.6, 129.1, 134.5,
136.7, 138.1, 155.4, 163.9. Anal. Calcd for C16H13NS2: C, 67.81; H,
4.62; N, 4.94. Found: C, 67.91; H, 4.72; N, 4.62.
Supporting information for this article is available online at
https://doi.org/10.1055/s-0040-1707258. SuprtigInfrmatioSnuprtigInfrmation
References and Notes
(14) 3-Alkyl-4-aryl-4-hydroxy-1,3-thiazolidine-2-thiones
6a–i;
(1) (a) Tomotsu, N.; Ishihara, N.; Newman, T. H.; Malanga, M. T. J.
Mol. Catal. A: Chem 1998, 128, 167. (b) Chien, J. C. W.; Salajka, Z.;
Dong, S. Macromolecules 1992, 25, 3199.
(2) Cheng, K.; Huang, L.; Zhang, Y. Org. Lett. 2009, 11, 2908.
(3) Reddi, R. N.; Prasad, P. K.; Sudalai, A. Org. Lett. 2014, 16, 5674.
(4) Prasad, P. K.; Reddi, R. N.; Sudalai, A. Org. Lett. 2016, 18, 500.
(5) Wu, C.-S.; Liu, R.-X.; Ma, D.-Y.; Luo, C.-P.; Yang, L. Org. Lett. 2019,
21, 6117.
(6) (a) Li, G.; Yan, Q.; Gan, Z.; Li, Q.; Dou, X.; Yang, D. Org. Lett. 2019,
21, 7938. (b) Halimehjani, A. Z.; Hasani, L.; Alaei, M. A.; Saidi, M.
R. Tetrahedron Lett. 2016, 57, 883. (c) Azizi, N.; Aryanasab, F.;
Torkiyan, L.; Ziyaei, A.; Saidi, M. R. J. Org. Chem. 2006, 71, 3634.
(d) Azizi, N.; Aryanasab, F.; Saidi, M. R. Org. Lett. 2006, 8, 5275.
(e) Khoudary, K.; Mona, S.; Matar, M.; Haffar, S. Asian J. Chem.
2013, 25, 962. (f) Gan, S.-F.; Wan, J.-P.; Pan, Y.-J.; Sun, C.-R.
Synlett 2010, 973.
(7) (a) Marinovich, M.; Viviani, B.; Capra, V.; Corsini, E.; Anselmi, L.;
D’Agostino, G.; Di Nucci, A.; Binaglia, M.; Tonini, M.; Galli, C. L.
Chem. Res. Toxicol. 2002, 15, 26. (b) Nieuwenhuizen, P. J.; Ehlers,
A. W.; Haasnoot, J. G.; Janse, S. R.; Reedijk, J.; Baerends, E. J. J.
Am. Chem. Soc. 1999, 121, 163. (c) Lai, J. T.; Shea, R. J. Polym. Sci.,
Part A: Polym. Chem. 2006, 44, 4298. (d) Bala, V.; Jangir, S.;
Mandalapu, D.; Gupta, S.; Chhonker, Y. S.; Lal, N.; Kushwaha, B.;
Chandasana, H.; Krishna, S.; Rawat, K. Bioorg. Med. Chem. Lett.
2015, 25, 881.
General Procedure
NBS (2.0 mmol) was added to a solution of the appropriate
styrene 1 (1.0 mmol) in H2O (2 mL), and the mixture was stirred
for 12 h at rt, then cooled to 0 °C. A mixture of the appropriate
primary amine (1.5 mmol) and CS2 (3 mmol) in H2O (1 mL) was
added, followed by K2CO3 (0.25 mmol), and the resulting
mixture was stirred for 5 h. The mixture was then extracted
with EtOAc (3 × 5 mL) and the organic layers were combined,
washed with brine, dried (Na2SO4), filtered, and concentrated in
vacuo. Finally, the residue was purified by chromatography
[silica gel, hexane–EtOAc (1:2)].
3-Benzyl-4-hydroxy-4-phenyl-1,3-thiazolidine-2-thione (6a)
White solid; yield: 229 mg (76%); mp 138–140 °C. IR (KBr):
3745, 3230, 3050, 2923, 2743, 1964, 1490, 1442, 1143, 699 cm–1
.
1H NMR (500 MHz, DMSO-d6):  = 3.63 (d, J = 12.5 Hz, 1 H), 3.75
(d, J = 12.5 Hz, 1 H), 4.50 (d, J = 15.5 Hz, 1 H), 4.83 (d, J = 15.5 Hz,
1 H), 7.14–7.21 (m, 5 H), 7.31–7.42 (m, 5 H), 7.79 (s, 1 H). 13C
NMR (100 MHz, DMSO-d6):  = 42.9, 49.2, 100.9, 126.1, 127.1,
128.1, 128.2, 128.9, 129.2, 137.1, 141.2, 196.0. Anal. Calcd for
C16H15NOS2: C, 63.75; H, 5.02; N, 4.65. Found: C, 63.72; H, 5.11;
N, 4.01.
(15) 2-Aryl-2-Oxoethyl Dithiocarbamates 7a–i; General Proce-
dure
NBS (2.0 mmol) was added to a solution of the appropriate
styrene 1 (1.0 mmol) in H2O (2 mL), and the mixture was stirred
for 12 h at rt, then cooled to 0 °C. A mixture of the appropriate
© 2020. Thieme. All rights reserved. Synlett 2020, 31, A–E

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F. Matloubi Moghaddam, M. Goudarzi
Letter
Synlett
secondary amine (1.5 mmol) and CS2 (3 mmol) in H2O (1 mL)
was added, followed by K2CO3 (0.25 mmol), and the resulting
mixture was stirred for 5 h. The mixture was extracted with
EtOAc (3 × 5 mL), and the organic layers were combined, washed
with brine, dried (Na2SO4), filtered, and concentrated in vacuo.
Finally, the residue was purified by chromatography [silica gel,
hexane–EtOAc (1:2)].
3736, 3354, 3058, 2978, 2930, 2874, 1683, 1586, 1492, 1205,
991, 687 cm–1. 1H NMR (500 MHz, CDCl3):  = 1.29 (t, J = 7.0 Hz,
3 H), 1.37 (t, J = 7.0 Hz, 3 H), 3.82–3.87 (m, 2 H), 4.02–4.06 (m, 2
H), 4.92 (s, 2 H), 7.51 (t, J = 7.5 Hz, 2 H), 7.61 (t, J = 7.0 Hz, 1 H),
8.09 (dd, J = 9.5 and 1.5 Hz, 2 H). 13C NMR (100 MHz, CDCl3):  =
11.5, 12.6, 45.1, 47.1, 50.1, 128.6, 128.7, 133.5, 136.2, 193.5,
194.0. Anal. Calcd for C13H17NOS2: C, 58.39; H, 6.41; N, 5.24.
Found: C, 58.44; H, 6.47; N, 4.96.
2-Oxo-2-phenylethyl Diethyldithiocarbamate (7a)
White solid; yield: 222 mg (83%); mp 108–110 °C. IR (KBr):
(16) Shinde, M. H.; Kshirsagar, U. A. Org. Biomol. Chem. 2016, 14, 858.
© 2020. Thieme. All rights reserved. Synlett 2020, 31, A–E