Ascorbic Acid Promoted Metal-Free Synthesis of Aryl Sulfides with Anilines Nitrosated in Situ by tert -Butyl Nitrite

Article abstract of DOI:10.1055/s-0034-1378738

A mild, metal-free synthesis of aryl sulfides has been disclosed. Aryl diazonium ion was generated by the in situ nitrosation of aniline, and it was reduced by ascorbic acid (vitamin C) to form aryl radical, which underwent a thiolation with disulfide to yield aryl sulfide. The reaction proceeded smoothly without heating or irradiation. This strategy was also expanded to the synthesis of aryl selenides.

Full text of DOI:10.1055/s-0034-1378738

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© Georg Thieme Verlag Stuttgart · New York
2015, 26, 1841–1846
letter
1841
M.-j. Bu et al.
Letter
Synlett
Ascorbic Acid Promoted Metal-Free Synthesis of Aryl Sulfides
with Anilines Nitrosated in Situ by tert-Butyl Nitrite
Mei-jie Bu
Guo-ping Lu
Chun Cai*
t-BuONO
NH2
X
ascorbic acid (0.5 equiv)
MeCN, 20 °C
R2
R1
R1
R2
X
R2
X
Chemical Engineering College, Nanjing University
of Science & Technology, Nanjing, Jiangsu 210094,
P. R. of China
X = S, Se; R1 = functional group; R2 = aryl, alkyl
one-pot, metal-free, mild conditions, promoted by vitamin C
c.cai@mail.njust.edu.cn
Received: 01.05.2015
Accepted after revision: 02.06.2015
Published online: 16.07.2015
but harsh conditions such as high temperature, the use of
strong base, and expensive ligands are often required in
many of these reactions. More recently, an efficient method
for C–S bond formation has been reported by several groups
that relies on the reaction of carbon-centered radicals and
disulfides under relatively mild conditions.9 Yet transition
metal or excess oxidants are still needed in some cases.
DOI: 10.1055/s-0034-1378738; Art ID: st-2015-w0334-l
Abstract A mild, metal-free synthesis of aryl sulfides has been dis-
closed. Aryl diazonium ion was generated by the in situ nitrosation of
aniline, and it was reduced by ascorbic acid (vitamin C) to form aryl rad-
ical, which underwent a thiolation with disulfide to yield aryl sulfide.
The reaction proceeded smoothly without heating or irradiation. This
strategy was also expanded to the synthesis of aryl selenides.
traditional Stadler–Ziegler reaction:
N2
Key words aryl sulfide, metal-free, ascorbic acid, carbon–sulfur bond
formation, radical reaction
S
M
S
R1
+
R2
R2
R1
Because carbon–sulfur bonds can be found in a great
number of natural products, pharmaceuticals, and func-
tional materials,1 as well as some ligands and chiral auxilia-
ries in synthetic chemistry,2 the development of new, effi-
cient approaches for the construction of C–S bond has be-
come a prominent area of research and been investigated by
many research groups over the past few decades.3 Aryl sul-
fides, typical structures of sulfur-containing compounds,
are valuable building blocks for the syntheses of fine chem-
icals and medicinal agents.4 The traditional approach to
generate aryl sulfides is the Stadler–Ziegler reaction,5
which has been studied and modified by several groups
over the last century.6 And now it is extensively applied in
industry. However, both diazonium salts and thiolates have
to be prepared in extra steps before the coupling reaction.
Recently, a modern version of the Stadler–Ziegler reaction
has been reported by Noël.7 In this chemistry, a variety of
aryl sulfides can be obtained by a single-step, one-pot pro-
cess facilitated by photoredox catalysis at room tempera-
ture. Transition-metal-catalyzed (Pd, Ni, Cu) cross-coupling
reactions of aryl halides with thiols or disulfides provides
another powerful and reliable approach to aryl sulfides,8
modern version of Stadler–Ziegler reaction facilitated by photoredox catalysis:
NH2
S
photoredox catalysis
R2
+ R2SH
R1
R1
RONO, acid (cat.), r.t.
transition-metal-catalyzed cross-coupling reactions:
X
S
transition metal
R2
R1
+ R2SH or R2SSR2
R1
base, ligand
high temperature
an efficient method for C–S bond formation under relatively mild conditions:
R1
S
R2SSR2
+
R2
R1
this work:
t-BuONO
ascorbic acid
S
NH2
R2
R2
S
R1
+
R1
R2
S
MeCN, 20 °C
3
• single step, one-pot
• neither heating, nor irradiation
1
2
Scheme 1 Comparison of various methods to generate aryl sulfides
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1841–1846

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M.-j. Bu et al.
Letter
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Aryl diazonium salts are valuable precursors of highly
active aryl radicals in the presence of suitable reducing
agents.10 Martin and Carrillo developed a direct C–H aryla-
tion of (hetero)arenes promoted by L-threo-ascorbic acid
(vitamin C).11 In this reaction, aniline was nitrosated in situ
to diazonium ion, which was reduced to aryl radical by
ascorbic acid in one pot. With our interest in the construc-
tion of the C–S bond,12 we decided to apply this method to
generate aryl radical which undergoes a thiolation with di-
sulfide. Herein, we report a metal-free, one-pot synthesis of
aryl sulfides promoted by ascorbic acid with anilines nitro-
sated in situ (Scheme 1).
In a typical experiment, the reaction of 4-chloroaniline
(1a) and 1,2-diphenyldisulfane (2a) in DMSO proceeded
very well under mild conditions. Conversion of 1a was com-
plete, and the reaction gave the product 3a in 70% yield. Dif-
ferent solvents and reaction times were screened to opti-
mize the reaction conditions. The results revealed that ace-
tonitrile (Table 1, entry 3) was the best solvent for this
reaction. Replacing DMSO with acetonitrile, an improved
yield of 91% was obtained. However, only a small amount of
products were detected when the reaction was conducted
in water, which is a good solvent for the generation of aryl
radicals from diazonium salts in other reactions.10d,13 When
the reaction time was cut to four hours, the yield was also
satisfactory (Table 1, entry 9). The yield reduced when the
reaction was exposed directly to air (Table 1, entry 10), be-
cause radicals formed during the reaction can be easily
quenched in the presence of oxygen.11,14 Irradiation is not
necessary for the reaction. When the reaction was carried
out in the dark, the yield hardly changed (Table 1, entry 11),
so the possibility of photoredox catalysis7,9a can be ruled
out. However, the amount of 3a declined sharply when no
ascorbic acid was added (Table 1, entry 12).
With these optimized reaction conditions in hand,15a
the scope of the reaction was explored with different ani-
lines. The results are shown in Table 2. In general, all the an-
ilines in Table 2 carrying electron-withdrawing, electron-
neutral, and electron-donating substituents at the para po-
sition gave the products with good yields. Substituents, in-
cluding halo, nitro, cyano, carboxyl, alkyl, and alkyloxy,
were all tolerated in this reaction. It is worth noting that
the reaction of heterocyclic amine 1j provided the corre-
sponding product 3j in a good yield. Carbon–halogen bonds
remained intact during the reaction, and they can be fur-
ther functionalized via transition-metal-catalyzed reac-
tions.
Table 1 Optimization of Reaction Conditionsa
NH2
Cl
ascorbic acid
t-BuONO
S
1a
+
Table 2 Scope of Anilinesa
solvent, 20 °C
Cl
S
3a
NH2
S
R1
2a
ascorbic acid (0.5 equiv)
S
1
t-BuONO (1.5 equiv)
R1
+
Entry
Solvent
Time (h)
Yield (%)b
MeCN, 20 °C, 4 h
1
2
DMSO
DMF
12
12
12
12
12
12
12
1
70
41
91
32
12
16
30
65
90
68
90
35
3
S
S
3
MeCN
CH2Cl2
THF
2a
4
5
Entry Substrate
Product
Yield (%)b
90
6
H2O
NH2
S
7
1,4-dioxane
MeCN
MeCN
MeCN
MeCN
MeCN
1
8
Cl
1a
Cl
3a
9
4
10c
11d
12e
4
NH2
S
S
4
2
92
76
O2N
1b
O2N
3b
4
a Reaction conditions: 1a (0.2 mmol), 2a (0.2 mmol), ascorbic acid (0.1
mmol) in DMSO (0.1 mL), t-BuONO (0.3 mmol), solvent (1 mL), inert atmo-
sphere, 20 °C.
O2N
NH2
O2N
3
b Isolated yields.
c The reaction was carried out under air.
d The reaction was carried out in the dark.
e No ascorbic acid was added.
1c
3c
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1841–1846

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Table 2 (continued)
Entry Substrate
drawing, electron-neutral, and electron-donating substitu-
ents all reacted smoothly, including heterocyclic aromatic
disulfide 2s, and gave the desired diaryl sulfides in good to
excellent yields. Dialkyl disulfides 2t–x were also found to
be good thiolation reagents for this reaction, and arylalkyl
sulfides were obtained (Table 3, entries 8–12). It was also
found that the reaction was compatible with either the di-
sulfide with hydroxyl groups (3w, Table 3, entry 11) or
dibenzyl disulfide (3x, Table 3, entry 12).
Product
Yield (%)b
NO2
S
NH2
4
89
NO2
1d
3d
NH2
S
5
6
7
8
9
93
92
87
68
77
NC
NC
Table 3 Scope of Disulfidesa
1e
3e
NH2
NH2
S
O2N
EtO2C
1f
EtO2C
3f
ascorbic acid (0.5 equiv)
t-BuONO(1.5 equiv)
S
1b
R2
+
S
NH2
MeCN, 20 °C, 4 h
O2N
S
R2
R2
S
3
HO2C
3g
HO2C
1g
2
NH2
S
Entry
R2
Product
Yield (%)b
92
F3C
1h
F3C
3h
S
NH2
1
2
Ph
S
S
O2N
3b
F
1i
F
3i
S
MeO2C
4-MeC6H4
4-MeOC6H4
4-ClC6H4
88
81
91
80
74
76
NH2
O2N
3n
10
76
S
S
CO2Me
NH2
S
1j
3j
3
4
5
6
7
S
O2N
OMe
3o
11
12
86
91
1k
3k
S
S
NH2
O2N
3p
Cl
MeO
3l
MeO
1l
S
OMe
OMe
4-BrC6H4
O2N
Br
NH2
S
3q
13
81
S
NO2
OMe
1m
OMe
3m
3-O2NC6H4
O2N
a Reaction conditions: 1 (0.2 mmol), 2a (0.2 mmol), ascorbic acid (0.1 mmol)
in DMSO (0.1 mL), t-BuONO (0.3 mmol), MeCN (1 mL), inert atmosphere,
3r
S
20 °C, 4 h.
b Isolated yields.
O
O
O2N
3s
Having established the scope of aniline, various disul-
fides were surveyed to investigate the scope of the reaction
(Table 3). A range of diaryl disulfides with electron-with-
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1841–1846

1844
M.-j. Bu et al.
Letter
Synlett
Table 3 (continued)
In summary, we have developed a general and efficient
ascorbic acid promoted carbon–sulfur bond formation un-
der mild conditions. The reaction provides the desired
product with a high yield and tolerates a variety of func-
tional groups. Comparing to the traditional Stadler–Ziegler
reaction and Noël’s modern version, this one-pot procedure
is simple, metal-free, and requires neither heating nor irra-
diation. This strategy could also be used in the construction
of carbon–selenium bond.
Entry
R2
Product
Yield (%)b
85
SMe
8c
Me
O2N
3t
S
9c
10
11
n-Pr
78
79
70
O2N
3u
Acknowledgment
S
We gratefully acknowledge Natural Science Foundation of Jiangsu
Province (BK 20131346) for financial support.
Cy
O2N
3v
S
Supporting Information
OH
CH2CH2OH
Supporting information for this article is available online at
O2N
http://dx.doi.org/10.1055/s-0034-1378738.
S
u
p
p
ortiInfogrmoaitn
S
u
p
p
o
nrtogI
f
rmoaitn
3w
References and Notes
S
12
Bn
82
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Sci., Part A: Polym. Chem. 2004, 42, 5301. (g) Clemenson, P. I.
Coord. Chem. Rev. 1990, 106, 171.
O2N
3x
a Reaction conditions: 1b (0.2 mmol), 2 (0.2 mmol), ascorbic acid (0.1 mmol)
in DMSO (0.1 mL), t-BuONO (0.3 mmol), MeCN (1 mL), inert atmosphere,
20 °C, 4 h.
b Isolated yields.
c With 2 equiv of the disulfide.
(2) (a) McGarrigle, E. M.; Myers, E. L.; Illa, O.; Shaw, M. A.; Riches, S.
L.; Aggarwal, V. K. Chem. Rev. 2007, 107, 5841. (b) Arrayas, R. G.;
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hedron Lett. 1988, 29, 4185.
Selenium serves as an important structure motif in
many organic compounds. There has been a growing inter-
est in the synthesis of organoselenium because of its vari-
ous biological functions.16 Encouraged by the successful
synthesis of aryl sulfides, we attempted to apply the strate-
gy to carbon–selenium bond formation (Scheme 2).15b Un-
der the same conditions, the reaction of aniline and disele-
nide proceeded smoothly, affording the desired selenides in
yields of 86–93%.
The reaction might follow a radical pathway, so a radi-
cal-capturing experiment was conducted (Scheme 3, a).15c
The adduct 6 afforded by the experiment indicated the
presence of aryl radical 9. According to this observation and
previous literature reports,9,11 a suggested mechanism was
proposed as depicted in Scheme 3 (b). The aniline 1 under-
goes a nitrosation by tert-butyl nitrite to give the aryl dia-
zonium salt 7, which is protonated by ascorbic acid, and the
diazonium salt 8 is formed upon the change of anion. Then,
an electron transfers from ascorbate to aryl diazonium ion
to generate the aryl radical 9. The resulting ascorbyl radical
dismutates into dehydroascorbic acid and ascorbic acid
(Scheme 3, c),17 which can react with another diazonium
salt 7. Finally, the radical intermediate 9 reacts with disul-
fide 2 to generate the product 3.
(7) Wang, X.; Cuny, G. D.; Noël, T. Angew. Chem. Int. Ed. 2013, 52,
7860.
(8) (a) Hartwig, J. F. Acc. Chem. Res. 2008, 41, 1534. (b) Carril, M.;
SanMartin, R.; Dominguez, E. Chem. Soc. Rev. 2008, 37, 639.
(c) Beletskaya, I. P.; Cheprakov, A. V. Coord. Chem. Rev. 2004,
248, 2337. (d) Prim, D.; Campagne, J.-M.; Joseph, D.; Andrioletti,
B. Tetrahedron 2002, 58, 2041. (e) Kunz, K.; Scholz, U.; Ganzer,
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1841–1846

1845
M.-j. Bu et al.
Letter
Synlett
ascorbic acid (0.5 equiv)
Se
NH2
+
t-BuONO (1.5 equiv)
Se
R1
R1
Se
MeCN, 20 °C, 6 h
1
4
5
Se
Se
Se
Se
O2N
NC
Cl
MeO
5a, 93%
Scheme 2 Reaction of diselenide with aniline
5b, 90%
5c, 86%
5d, 89%
(9) (a) Majek, M.; von Wangelin, A. J. Chem. Commun. 2013, 49,
5507. (b) Du, B.; Jin, B.; Sun, P. Org. Lett. 2014, 16, 3032. (c) Guo,
S.-r.; Yuan, Y.-q.; Xiang, J.-n. Org. Lett. 2013, 15, 4654. (d) Wang,
P. F.; Wang, X. Q.; Dai, J. J.; Feng, Y. S.; Xu, H. J. Org. Lett. 2014, 16,
4586.
O
N
a)
t-BuONO
ascorbic acid
NH2
+
O
N
MeCN
O2N
O2N
(10) (a) Sandmeyer, T. Ber. Dtsch. Chem. Ges. 1884, 17, 1633.
(b) Meerwein, H.; Büchner, E.; van Emster, K. J. Prakt. Chem.
1939, 152, 237. (c) Kosynkin, D.; Bockman, T. M.; Kochi, J. K. J.
Am. Chem. Soc. 1997, 119, 4846. (d) Wetzel, A.; Pratsch, G.; Kolb,
R.; Heinrich, M. R. Chem. Eur. J. 2010, 16, 2547. (e) Hartmann,
M.; Studer, A. Angew. Chem. Int. Ed. 2014, 53, 8180. (f) Matheis,
C.; Jouvin, K.; Goossen, L. J. Org. Lett. 2014, 16, 5984.
(11) Crisostomo, F. P.; Martin, T.; Carrillo, R. Angew. Chem. Int. Ed.
2014, 53, 2181.
(12) (a) Lu, G.-p.; Cai, C. Adv. Synth. Catal. 2013, 355, 1271. (b) Feng,
J.; Lv, M.; Lu, G.; Cai, C. Eur. J. Org. Chem. 2014, 5312. (c) Lu,
G.-p.; Cai, C. RSC Adv. 2014, 4, 59990.
(13) (a) Galli, C. Chem. Rev. 1988, 88, 765. (b) Wetzel, A.; Ehrhardt, V.;
Heinrich, M. R. Angew. Chem. Int. Ed. 2008, 47, 9130.
(14) Hofmann, J.; Jasch, H.; Heinrich, M. R. J. Org. Chem. 2014, 79,
2314.
1b
TEMPO
6, 61%
b)
t-BuO
N
NH2
N
t-BuONO
R1
R1
H2O
1
7
H2Asc
DAsc
t-BuOH
N
N
R1
HAsc
HAsc
(15) (a) General Procedure for the Synthesis of Aryl Sulfides 3
With Solid Disulfides
8
A 10 mL Schlenk tube with a magnetic stirring bar was charged
with aniline 1 (0.2 mmol) and disulfide 2 (0.2 mmol). The tube
was evacuated and backfilled with dry nitrogen (this operation
was repeated three times). MeCN (1 mL) was added by syringe,
followed by L-ascorbic acid (0.5 equiv, 20 mg) dissolved in
DMSO (0.1 mL).
S
R2
1/2 (R2SSR2)
R1
R1
3
9
c)
With Liquid Disulfides
A 10 mL Schlenk tube with a magnetic stirring bar was charged
with aniline 1 (0.2 mmol). The tube was evacuated and back-
filled with dry nitrogen (this operation was repeated three
times). MeCN (1 mL) was added by syringe, followed by disul-
fide 2 (0.2 mmol or 0.4 mmol) and L-ascorbic acid (0.5 equiv, 20
mg) dissolved in DMSO (0.1 mL).
HO
HO
HO
HO
HO
H
H
H
O
O
O
O
O
O
+
HO
O
OH
HO
OH
O
O
The mixture was stirred vigorously for 1 min before t-BuONO
(0.3 mmol, 36 μL) was added via syringe. After the resulting
mixture was stirred at 20 °C for 4 h, the solvent was removed
under reduced pressure. Purification of the crude product was
achieved by column chromatography.
ascorbic acid
(H2Asc)
ascorbyl radical
(HAsc )
dehydroascorbic acid
(DAsc)
Scheme 3 Proposed reaction mechanism
(4-Chlorophenyl)(phenyl)sulfane (3a)
D. Synlett 2003, 2428. (f) Alvaro, E.; Hartwig, J. F. J. Am. Chem.
Soc. 2009, 131, 7858. (g) Fernández-Rodríguez, M. A.; Shen, Q.;
Hartwig, J. F. Chem. Eur. J. 2006, 12, 7782. (h) Fukuzawa, S.-i.;
Tanihara, D.; Kikuchi, S. Synlett 2006, 2145. (i) Bhadra, S.;
Sreedhar, B.; Ranu, B. C. Adv. Synth. Catal. 2009, 351, 2369.
(j) Zhang, Y.; Ngeow, K. C.; Ying, J. Y. Org. Lett. 2007, 9, 3495.
1H NMR (500 MHz, CDCl3): δ = 7.40–7.30 (m, 4 H), 7.30–7.20 (m,
5 H). 13C NMR (125 MHz, CDCl3): δ = 135.2, 134.8, 133.1, 132.1,
131.4, 129.4, 127.6. GC–MS: m/z = 220 [M+].
Phenyl [4-(Trifluoromethyl)phenyl]sulfane (3h)
1H NMR (500 MHz, CDCl3): δ = 7.51–7.46 (m, 4 H), 7.43–7.36 (m,
3 H), 7.27 (d, J = 8.4 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ =
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1841–1846

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Synlett
142.9, 133.6, 132.6, 129.8, 128.8, 128.4, 128.0, 125.9, 125.3,
123.1. 19F NMR (470 MHz, CDCl3): δ = –62.5. GC–MS: m/z = 254
[M+].
Methyl 3-(Phenylthio)thiophene-2-carboxylate (3j)
1H NMR (500 MHz, CDCl3): δ = 7.63–7.57 (m, 2 H), 7.46–7.40 (m,
3 H), 7.30 (d, J = 5.3 Hz, 1 H), 6.35 (d, J = 5.3 Hz, 1 H), 3.92 (s, 3
H). 13C NMR (125 MHz, CDCl3): δ = 162.7, 145.4, 135.1, 132.6,
130.6, 129.7, 129.4, 128.2, 121.4, 52.2. GC–MS: m/z = 250 [M+].
(2,5-Dimethoxyphenyl)(phenyl)sulfane (3m)
(4-Nitrophenyl)(phenyl)selane (5a)
1H NMR (500 MHz, CDCl3): δ = 8.09–7.97 (m, 2 H), 7.63 (dd, J =
8.1, 1.2 Hz, 2 H), 7.47–7.38 (m, 3 H), 7.38–7.31 (m, 2 H). 13C
NMR (125 MHz, CDCl3): δ = 146.3, 144.1, 136.0, 130.2, 129.8,
129.5, 127.3, 124.1. GC–MS: m/z = 279 [M+].
(c) Radical-Capturing Experiment
A 25 mL Schlenk tube with a magnetic stirring bar was charged
with 4-nitroaniline 1b (0.5 mmol, 70 mg) and 2,2,6,6-
tetramethyl-1-piperidinyloxy (TEMPO, 0.55 mmol, 87 mg). The
tube was evacuated and backfilled with dry nitrogen (this oper-
ation was repeated three times). MeCN (2.5 mL) was added by
syringe, followed by L-ascorbic acid (0.5 equiv, 50 mg) dissolved
in DMSO (0.25 mL). The mixture was stirred vigorously for 1
min before t-BuONO (0.75 mmol, 90 μL) was added via syringe.
After the resulting mixture was stirred at 20 °C for 6 h, the
solvent was removed under reduced pressure. Purification of
the crude was achieved by column chromatography.
2,2,6,6-Tetramethyl-1-(4-nitrophenoxy)piperidine (6)
1H NMR (500 MHz, CDCl3): δ = 8.14 (d, J = 9.5 Hz, 2 H), 7.27 (br, 2
H), 1.73–1.57 (m, 5 H), 1.48–1.40 (m, 1 H), 1.23 (s, 6 H), 0.98 (s,
6 H). 13C NMR (125 MHz, CDCl3): δ = 168.8, 141.2, 125.6, 114.3,
61.0, 39.7, 32.3, 20.5, 17.0. GC–MS: m/z = 278 [M+].
1H NMR (500 MHz, CDCl3): δ = 7.39 (dt, J = 3.3, 1.9 Hz, 2 H),
7.36–7.30 (m, 2 H), 7.30–7.26 (m, 1 H), 6.85–6.81 (m, 1 H), 6.73
(dd, J = 8.9, 3.0 Hz, 1 H), 6.60 (d, J = 3.0 Hz, 1 H), 3.83 (s, 3 H),
3.66 (s, 3 H). 13C NMR (125 MHz, CDCl3): δ = 154.1, 151.5, 133.9,
132.3, 129.4, 127.6, 125.9, 116.9, 112.6, 111.9, 56.7, 55.8. GC–
MS: m/z = 246 [M+].
2-Methyl-3-[(4-nitrophenyl)thio]furan (3s)
1H NMR (500 MHz, CDCl3): δ = 8.11–8.04 (m, 2 H), 7.46 (d, J =
1.9 Hz, 1 H), 7.17–7.12 (m, 2 H), 6.40 (d, J = 1.9 Hz, 1 H), 2.35 (s,
3 H). 13C NMR (125 MHz, CDCl3): δ = 158.1, 148.4, 145.2, 142.1,
125.2, 124.2, 115.2, 105.6, 12.0. GC–MS: m/z = 235 [M+].
(b) General Procedure for the Synthesis of Aryl Selenides 5
A 10 mL Schlenk tube with a magnetic stirring bar was charged
with aniline 1 (0.2 mmol) and 1,2-diphenyldiselane (4, 0.2
mmol, 63 mg). The tube was evacuated and backfilled with dry
nitrogen (this operation was repeated three times). MeCN (1
mL) was added by syringe, followed by L-ascorbic acid (0.5
equiv, 20 mg) dissolved in DMSO (0.1 mL). The mixture was
stirred vigorously for 1 min before t-BuONO (0.3 mmol, 36 μL)
was added via syringe. After the resulting mixture was stirred at
20 °C for 6 h, the solvent was removed under reduced pressure.
Purification of the crude product was achieved by column chro-
matography.
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© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1841–1846