Cyanide-Mediated Synthesis of Sulfones and Sulfonamides from Vinyl Sulfones

Article abstract of DOI:10.1055/s-0039-1690991

We report a facile synthesis of sulfones, β-keto sulfones, and sulfonamides from vinyl sulfones via an addition-elimination sequence where in situ generation of nucleophilic sulfinate ion is mediated by cyanide. The use vinyl sulfones renders high selectivity for S -alkylation to produce sulfones in high yields. In the presence of N -bromosuccinimide, primary and secondary amines underwent sulfonamide formation. A preliminary mechanistic study showed the formation of acrylonitrile as an innocent byproduct, without interfering with the desired reaction pathway while generating a sulfinate nucleophile.

Full text of DOI:10.1055/s-0039-1690991

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© Georg Thieme Verlag Stuttgart · New York
2019, 30, A–D
cluster
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T. Roy, J.-W. Lee
Cluster
Synlett
Cyanide-Mediated Synthesis of Sulfones and Sulfonamides from
Vinyl Sulfones
O
O
O
O
O
NR1R2
Tamal Roy
1) CN
up to 95% yield
17 examples
S
or
S
S
R
R'
R
2) R'X or NR1R2/NBS
rt, <1 h
R
Ji-Woong Lee*
0
0
0
0-0
0
0
1-6
1
7
7-
4
5
6
9
O
R = Ar, Alkyl
• high yields, short reaction time
• operationally simple
• easy purification
CN H+, base
O
Department of Chemistry, Nano-Science Center, University
of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø,
Denmark
S
Ph SO2
Ph
O
• odorless sulfone synthesis
1,4-addition
CN
elimination
jiwoong.lee@chem.ku.dk
Published as part of the Special Section 11th EuCheMS Organic
Division Young Investigator Workshop
Received: 21.08.2019
Accepted after revision: 05.09.2019
Published online: 24.09.2019
perature (Scheme 1, C).4 However, the process still requires
elevated reaction temperatures (>90 °C) and longer reaction
times to achieve the desired transformation.
DOI: 10.1055/s-0039-1690991; Art ID: st-2019-b0441-c
A. Oxidation of sulfide and sulfone5,6
Abstract We report a facile synthesis of sulfones, -keto sulfones, and
sulfonamides from vinyl sulfones via an addition–elimination sequence
where in situ generation of nucleophilic sulfinate ion is mediated by
cyanide. The use vinyl sulfones renders high selectivity for S-alkylation
to produce sulfones in high yields. In the presence of N-bromosuccinim-
ide, primary and secondary amines underwent sulfonamide formation.
A preliminary mechanistic study showed the formation of acrylonitrile
as an innocent byproduct, without interfering with the desired reaction
pathway while generating a sulfinate nucleophile.
O
O
O
S
[oxidant]
catalyst
S
S
S
or
R
R'
R
R'
R
R'
B. Sodium sulfinate as a nucleophile6–8
SO2Na
O
O
R
R'X
+
R
R'
low solubility in
organic solvents
C. Thiosulfonate for in situ generation of sulfinate ion11
Key words cyanide, sulfonate, sulfones, sulfonamides, vinyl sulfones
O
O
Cs2CO3
O
O
S
+
S
R'X
R
R'
EtOH, >90 °C
16 h
R
SPh
Compounds comprising sulfur(IV), for instance, sulfones
and sulfonamides are useful synthetic targets for organic
chemists attributable to their unique biological activities
and utility as building blocks and catalysts in several organ-
ic transformations.1 Typically, sulfonyl derivatives are syn-
thesized from the oxidation of sulfides or sulfoxides
(Scheme 1, A).2 However, these routes suffer shortcomings,
i.e., multiple synthetic steps, use of over-stoichiometric
amount of strong oxidizing agents, elevated temperatures,
extended reaction time, and unendurable odor of thiols.
Sulfinated salts are an adequate alternative to access sul-
fone functional groups via nucleophilic substitution reac-
tions at sulfur.2b Recent developments in sulfinate deriva-
tives in sulfonylative couplings and desulfinative couplings
showed promising reactivity patterns.3 However, the intrin-
sic low solubility of sulfinate salts in organic solvents pro-
hibits general applications with electrophilic reagents (R′X,
Scheme 1, B). Recently, Shyam et al. reported the use of
thiosulfonates to in situ generate the sulfinate anion, which
then subsequently reacted with various alkyl halides or
amines to afford sulfones or sulfonamides at elevated tem-
D. This work:
via:
O
S
O
NEt4CN
then R'X
O
O
CN
S
S
R
O
R
R'
Ph
O
Scheme 1 Conventional routes to access sulfones: (A) Oxidation of sul-
fides and sulfoxides, (B) nucleophilic substitution reaction of metal sulfi-
nates, and (C) thiosulfonates to generate sulfinates. (D) This work
represents devinylation to access nucleophilic sulfinate ions for substi-
tution reactions.
During our investigation on the reactivity of cyanide
with carbon dioxide and electrophiles,5 we observed that
commercially available vinyl sulfones were decomposed
presumably to acrylonitrile and sulfinate anion. Therefore,
we anticipated that the in situ generated sulfinate anion can
be a useful intermediate for substitution reactions with
electrophilic partners to access sulfones and sulfonamides
(Scheme 1, D). This reaction would involve an addition–
elimination sequence of vinyl sulfones, converting this
common electrophilic Michael acceptor into nucleophilic
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–D
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
T. Roy, J.-W. Lee
Cluster
Synlett
sulfinate.6 Furthermore, the generation of sulfinates from
an accessible source would be an interesting alternative for
transition-metal-catalyzed C–H activation7 and photoredox
catalysis,8 where promising reactivities are shown with sul-
fur(IV) derivatives.
Table 1 Optimization of the Reaction Conditionsa
1) MCN (1.05–2 equiv)
2) BnBr (1.05 equiv)
CN
O
O
O
O
O
O
O
S
S
S
Ph
S
solvents, rt
Ph
4a, not observed
Ph
Ph
Ph
OEt
1a
2a
3a
We commenced our investigation under previously es-
tablished experimental conditions5a using phenyl vinyl sul-
fone (1a) as a model electrophile. We observed no trace of
the corresponding cyanide adduct, although complete con-
sumption of the starting material was detected. Kiyokawa
et al. reported the transformation of vinyl sulfones to 1,2-
dicyanoalkanes mediated by TMSCN and tetrabutylammo-
nium fluoride.6 Based on our observation, the absence of
cyanated product with phenyl vinyl sulfone suggested a
possible concerted addition–elimination reaction. To estab-
lish our hypothesis, benzyl bromide was employed to the
reaction mixture, resulting in a rapid formation of (benzyl-
sulfonyl)benzene (2a) with a yield of 90% in 15 minutes (Ta-
ble 1, entry 1). Without strict anhydrous atmosphere, a
clean reaction profile was obtained, indicating high selec-
tivity toward the desired product 2a under ambient reac-
tion conditions.
The absence of any O-benzylated product under the
present reaction conditions is notable.9 The use of sodium
benzenesulfinate as a surrogate under the same reaction
conditions afforded less than 10% yield of the desired prod-
uct, highlighting the advantage of in situ generation of the
sulfinate via de-vinylation (Table 1, entry 2). The use of so-
dium benzenesulfonate together with stoichiometric
amount of tetrabutylammonium bromide as a phase-trans-
fer reagent furnished 2a in moderate yield even at higher
temperatures (60% at room temperature and 76% at 80 °C,
entries 3 and 4, respectively). These results indicate that the
solubility of sulfinate anion is important to attain the de-
sired reactivity of the nucleophilic sulfinate. Based on the
well-established phase-transfer reaction mechanism, NaCN
and KCN were employed as a cyanide source, which afford-
ed moderate yields of the desired product 2a in the pres-
ence of NBu4I as a phase-transfer catalyst (54–56% yield, Ta-
ble 1, entries 5 and 6). Soluble cyanide sources such as
TMSCN and acetone cyanohydrin were found to be ineffec-
tive to generate product 2a. A quick optimization of the sol-
vents showed both DCM and THF are optimum (Table 1, en-
tries 11 and 12). A protic solvent, ethanol, afforded the for-
mation of ethyl sulfonate (O-ethylated product 3a, 35%) as a
predominant product over the S-benzylated product (2a,
22%, Table 1, entry 14). To our delight, the reaction could
also be carried out in neat water but at the cost of dimin-
ished reactivity and product yield (60% yield, 2 h, Table 1,
entry 15).
Entry
Solvent
Cyanide source
Time (min) Yield (%)b
1
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
DMF
NEt4CN
–
15
30
90
<10
60
2c
3c,d
–
15
4c,e,f
5e
6e
7
–
960
960
120
960
120
76
NaCN
KCN
Zn(CN)2
TMSCN
56
54
n.d.
n.d.
n.d.
85
8
9
acetone cyanohydrin 960
10
NEt4CN
NEt4CN
NEt4CN
NEt4CN
NEt4CN
NEt4CN
15
15
11
12
13
14
15
DCM
99
THF
30
96
toluene
EtOH
120
30
20
22
water
120
60
a Reaction conditions: phenyl vinyl sulfone (0.4 mmol), NEt4CN (1.05
equiv)/other cyanides (2 equiv), benzyl bromide (1.05 equiv), solvent (1
mL).
b NMR yield using 1,3,5-trimethoxybenzene as an internal standard; n.d. =
not detected.
c Sodium benzenesulfinate was used instead of phenyl vinyl sulfone and a
cyanide source.
d 100 mol% of n-Bu4NBr were added.
e 10 mol% of n-Bu4NI were added.
f Reaction mixture was heated at 80 °C.
isolated yields. The alkylation using a secondary alkyl bro-
mide, i.e., 2-bromopropane, was expectedly slower; howev-
er, we obtained moderate yield of the corresponding prod-
uct 2f, together with a small amount of O-alkylated product
3f. Bulkier alkyl bromides or alkyl chlorides were found to
be inefficient as an alkylating agent under current opti-
mized conditions. We noticed slight drop in isolated yield of
products 2i (82% yield) and 2j (84% yield), when methyl-
(1b) and ethyl (1c) vinyl sulfones were used as starting ma-
terials instead of phenyl vinyl sulfone (1a), respectively.
-Keto sulfones are lately drawing significant attention
as synthetic targets2b,10 due to their biological activities11
and widespread applications as synthons in organic synthe-
sis.12 We extended the application of current synthetic pro-
tocol for the synthesis of -keto sulfones using -bromo ke-
tones as electrophiles. To our delight, we obtained high iso-
lated yield of -sulfone phenyl ketone (2k) under optimized
reaction conditions without complicated purification steps.
Methyl and ethyl vinyl sulfones were also tolerant to afford
the corresponding sulfones 2l and 2m in good isolated
yields (82% and 85%, respectively).
Under optimized conditions, several aryl alkyl sulfone
derivatives were prepared (Scheme 2). Both alkyl iodides
and alkyl bromides were found to be adequate choices as al-
kylating agent, furnishing corresponding sulfones in high
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–D

C
T. Roy, J.-W. Lee
Cluster
Synlett
solvent.6 Our direct observation of the elimination product,
acrylonitrile, manifested the suggested mechanism
(Scheme 1, D). In the crude reaction mixture, we detected
the formation of acrylonitrile before the addition of an al-
kylating agent (Figure 1, red). The elimination reaction was
instantaneous and quantitative; however, we presumed
that some of acrylonitrile was evaporated during the prepa-
ration for the NMR measurement due to the low boiling
point of acrylonitrile. We ruled out any radical mechanisms
due to the lack of negative effects with TEMPO as a radical
scavenger in the alkylation reaction with benzyl bromide.
The presence of sulfinate was unambiguously confirmed by
ESI-MS showing quantitative conversion of the vinyl sul-
fone (1a) into the corresponding sulfinate mediated by
cyanide (see Supporting Information, Figure S1).
O
O
O
O
R2
NEt4CN
R2-X
+
S
S
+
DCM, rt
0.5–1 h
R1
R1
(1.05 equiv)
(1.05 equiv)
1a–c
2a–m
O
S
O
O
O
O
O
O
O
Ph
S
S
S
Me
Ph
Ph
Ph
Ph
2a, 94%
2c, 94%
2b, 92%
2d, 92%
O
O
O
S
O
S
O
O
S
10
Ph
Ph
Ph
2e, 89%
2f, 68%
(16 h)
2g, n.d.
O
O
O
O
O
O
S
S
Ph
S
Ph
Ph
Me
Et
2h, n.d.
2i, 82%
2j, 84%
β-keto sulfones:
O
O
O
O
S
O
S
O
O
O
O
S
CN H+, base
CN
O
O
Ph
Ph
Ph
1,4-addition
Ph
Me
Et
S
S
Ph SO2
Ph
Ph
O
O
2k, 92%
2l, 82%
2m, 85%
observed in
ESI-MS
1a
Scheme 2 Substrate scope in the synthesis of sulfones and -keto sul-
fones.
After establishing a facile and straightforward protocol
to access sulfones, we turned our attention to generate sul-
fonamides by forming halogenated amines as electrophiles.
A similar protocol was reported starting from primary and
secondary amines using NBS as an oxidant, generating elec-
trophilic nitrogen species at elevated temperatures
(Scheme 3).4 The use of vinyl sulfone as a starting material
enabled us to synthesize various sulfonamides from sec-
ondary and primary amines at room temperature via the
cyanide-mediated addition–elimination sequence. Under
ambient reaction conditions primary and secondary
amines were smoothly converted into the corresponding
sulfonamides with good to excellent yields (61–95% yield).
reaction mixture
acrylonitrile
substrate (1a)
Figure 1 Mechanistic study based on 1H NMR spectra of the reaction
mixture (red), a pure sample of acrylonitrile (blue) and the starting
material, phenyl vinyl sulfone (1a, black).
HNR2R3 (1.5 equiv)
NBS (1.5 equiv)
In conclusion, we demonstrated the in situ formation of
sulfinate ion, which was beneficial for conducting nucleop-
hilic substitution reactions and amination reaction to afford
sulfones13 and sulfonamides14 under mild reaction condi-
tions. Preliminary mechanistic studies revealed the sulfone
and sulfonamide formation reactions proceeded by expel-
ling acrylonitrile mediated by cyanide, while generating the
nucleophilic sulfinate ion. Further applications of in situ
generated sulfinate nucleophiles in olefin synthesis (Julia–
Kocienski type), asymmetric catalysis15 and CO2 functional-
ization16 are under way.
O
R1
1a
O
O
O
NEt4CN
(1.05 equiv)
+
S
S
R1 NR2R3
DCM, rt
1 h
4a–f
O
S
O
O
O
O
O
S
S
N
N
N
Ph
Ph
Ph
O
4a, 95%
4b, 90%
4c, 89%
O
O
O
O
O
O
nBu
S
S
S
N
N
N
Ph
Ph
Ph
Ph
Ph
H
H
Ph
4d, 72%
4e, 72%
4f, 61%
Scheme 3 Synthesis of sulfonamides.
Funding Information
To probe our suggested reaction mechanism, the Mi-
chael addition reaction of cyanide to vinyl sulfone was
monitored by H NMR spectroscopy in CDCl3 as a reaction
The generous support from the Department of Chemistry, University
of Copenhagen and the Novo Nordisk Fonden (Grant No.
1
NNF17OC0027598) is gratefully acknowledged.
N
o
v
o
N
ord
i
sk(N
N
F
1
7
O
C
0
0
2
7
5
9
8)
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–D

D
T. Roy, J.-W. Lee
Cluster
Synlett
Acknowledgment
appropriate electrophile (1.05 equiv, 0.42 mmol) in DCM (0.5
mL) was added dropwise. The resultant reaction mixture was
stirred at room temperature. After completion of the reaction
(checked by crude 1H NMR or GC–MS), water (10 mL) was added
to the reaction mixture, and the product was extracted with
ethyl acetate (3 × 10 mL). The combined organic layers were
washed with brine (10 mL), dried over anhydrous Na2SO4, and
concentrated under vacuum. The crude product thus obtained
was purified by column chromatography using 10–20% ethyl
acetate in petroleum ether.
The authors thank Christian Tortzen and Theis Brock-Nannestad for
their support in analysis.
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0039-1690991.
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(Benzylsulfonyl)benzene (2a)
Compound 2a (87 mg, 94%) was synthesized using the general
procedure for the synthesis of sulfones and isolated as a white
solid. H NMR (500 MHz, CDCl3):  = 7.66–7.56 (m, 3 H), 7.47–
7.42 (m, 2 H), 7.35–7.29 (m, 1 H), 7.28–7.23 (m, 2 H), 7.13–7.04
(m, 2 H), 4.31 (s, 2 H). 13C NMR (126 MHz, CDCl3):  = 138.0,
133.8, 131.0, 129.0, 128.9, 128.8, 128.7, 128.3, 63.0. HRMS (EI):
m/z calcd for C13H13O2S [M + H]+: 233.0636; found: 233.0636.
1-Phenyl-2-(phenylsulfonyl)ethan-1-one (2k)
References and Notes
1
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2019, 25, 11193.
(2) (a) Kupwade, R. V. J. Chem. Rev. 2019, 1, 99. (b) Liu, N.-W.; Liang,
S.; Manolikakes, G. Synthesis 2016, 48, 1939.
Compound 2k (96 mg, 92%) was synthesized using the general
procedure for the synthesis of sulfones and isolated as a white
(3) (a) Kaiser, D.; Klose, I.; Oost, R.; Neuhaus, J.; Maulide, N. Chem.
Rev. 2019, 119, 8701. (b) Aziz, J.; Messaoudi, S.; Alami, M.;
Hamze, A. Org. Biomol. Chem. 2014, 12, 9743. (c) Guyon, H.;
Chachignon, H.; Cahard, D. Beilstein J. Org. Chem. 2017, 13, 2764.
(4) Shyam, P. K.; Jang, H.-Y. J. Org. Chem. 2017, 82, 1761.
(5) (a) Roy, T.; Kim, M. J.; Yang, Y.; Kim, S.; Kang, G.; Ren, X.;
Kadziola, A.; Lee, H.-Y.; Baik, M.-H.; Lee, J.-W. ACS Catal. 2019, 9,
6006. (b) Juhl, M.; Lee, J.-W. Angew. Chem. Int. Ed. 2018, 57,
12318.
(6) Kiyokawa, K.; Nagata, T.; Hayakawa, J.; Minakata, S. Chem. Eur. J.
2015, 21, 1280.
(7) Liu, J.; Zheng, L. Adv. Synth. Catal. 2019, 361, 1710.
(8) Zhu, J.; Yang, W.-C.; Wang, X.-d.; Wu, L. Adv. Synth. Catal. 2018,
360, 386.
1
solid. H NMR (500 MHz, CDCl3):  = 7.95–7.93 (m, 2 H), 7.91–
7.89 (m, 2 H), 7.68–7.60 (m, 2 H), 7.60–7.54 (m, 2 H), 7.50–7.47
(m, 2 H), 4.74 (s, 2 H). 13C NMR (126 MHz, CDCl3):  = 188.1,
138.9, 135.9, 134.5, 134.4, 129.4, 129.4, 129.0, 128.7, 63.6.
HRMS (EI): m/z calcd for C14H13O3S [M + H]+: 261.0585; found:
261.0586.
(14) General Procedure for the Synthesis of Sulfonamides 4a–f
N-Bromosuccinimide (1.5 equiv, 0.6 mmol) was added portion-
wise to a vial containing a solution of an appropriate amine (1.5
equiv, 0.6 mmol) in DCM (1 mL). In another vial, vinyl sulfone
(0.4 mmol) and tetraethylammonium cyanide (1.05 equiv, 0.42
mmol) were taken together with DCM (1 mL) and stirred for 5
min. The later solution was then added dropwise to the former
mixture. The combined reaction mixture was allowed to stir at
room temperature. After completion of the reaction (checked by
(9) (a) Baidya, M.; Kobayashi, S.; Mayr, H. J. Am. Chem. Soc. 2010,
132, 4796. (b) Ji, Y.-Z.; Li, H.-J.; Zhang, J.-Y.; Wu, Y.-C. Eur. J. Org.
Chem. 2019, 1846.
1
crude H NMR and TLC), water (10 mL) was added to the reac-
tion mixture, and the product was extracted with ethyl acetate
(3 × 10 mL). The combined organic layers were washed with
brine (10 mL), dried over anhydrous Na2SO4, and concentrated
under vacuum. The crude product thus obtained was purified
by column chromatography using 10–20% ethyl acetate in
petroleum ether.
(10) (a) Muneeswara, M.; Sundaravelu, N.; Sekar, G. Tetrahedron
2019, 75, 3479. (b) Kumar, N.; Kumar, A. ACS Sustainable Chem.
Eng. 2019, 7, 9182. (c) Cai, S.; Chen, D.; Xu, Y.; Weng, W.; Li, L.;
Zhang, R.; Huang, M. Org. Biomol. Chem. 2016, 14, 4205.
(11) (a) Montgomery, J. I.; Brown, M. F.; Reilly, U.; Price, L. M.;
Abramite, J. A.; Arcari, J.; Barham, R.; Che, Y.; Chen, J. M.; Chung,
S. W.; Collantes, E. M.; Desbonnet, C.; Doroski, M.; Doty, J.;
Engtrakul, J. J.; Harris, T. M.; Huband, M.; Knafels, J. D.; Leach, K.
L.; Liu, S.; Marfat, A.; McAllister, L.; McElroy, E.; Menard, C. A.;
Mitton-Fry, M.; Mullins, L.; Noe, M. C.; O’Donnell, J.; Oliver, R.;
Penzien, J.; Plummer, M.; Shanmugasundaram, V.; Thoma, C.;
Tomaras, A. P.; Uccello, D. P.; Vaz, A.; Wishka, D. G. J. Med. Chem.
2012, 55, 1662. (b) Aranapakam, V.; Grosu, G. T.; Davis, J. M.;
Hu, B.; Ellingboe, J.; Baker, J. L.; Skotnicki, J. S.; Zask, A.;
DiJoseph, J. F.; Sung, A.; Sharr, M. A.; Killar, L. M.; Walter, T.; Jin,
G.; Cowling, R. J. Med. Chem. 2003, 46, 2361.
4-(Phenylsulfonyl)morpholine (4a)
Compound 4a (86 mg, 95%) was synthesized using the general
procedure for the synthesis of sulfonamides and isolated as a
1
white solid. H NMR (500 MHz, CDCl3):  = 7.78–7.74 (m, 2 H),
7.66–7.61 (m, 1 H), 7.59–7.54 (m, 2 H), 3.77–3.72 (m, 4 H),
3.03–2.98 (m, 4 H). 13C NMR (126 MHz, CDCl3):  = 135.3, 133.2,
129.3, 128.0, 66.2, 46.1. HRMS (EI): m/z calcd for C10H14NO3S
[M + H]+: 228.0694; found: 228.0693.
(15) (a) Yan, H.; Suk, Oh. J.; Lee, J.-W.; Song, C. E. Nat. Commun. 2012,
3, 1212. (b) Park, S. Y.; Liu, Y.; Oh, J. S.; Kweon, Y. K.; Jeong, Y. B.;
Duan, M.; Tan, Y.; Lee, J.-W.; Yan, H.; Song, C. E. Chem. Eur. J.
2018, 24, 1020. (c) Liu, Y.; Ao, J.; Paladhi, S.; Song, C. E.; Yan, H.
(12) Markitanov, Y. M.; Timoshenko, V. M.; Shermolovich, Y. G.
J. Sulfur Chem. 2014, 35, 188.
(13) General Procedure for the Synthesis of Sulfones 2a–m
Vinyl sulfone (0.4 mmol) and tetraethylammonium cyanide
(1.05 equiv, 0.42 mmol) were dissolved in DCM (1 mL). The
reaction mixture was stirred for 5 min, and a solution of an
J. Am. Chem. Soc. 2016, 138, 16486. For
a review, see:
(d) Oliveira, M. T.; Lee, J.-W. ChemCatChem 2017, 9, 377.
(16) Sun, S.; Yu, J.-T.; Jiang, Y.; Cheng, J. Adv. Synth. Catal. 2015, 357,
2022.
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–D