Metal-free synthesis of activated ynesulfonamides and tertiary enesulfonamides

Article abstract of DOI:10.1039/c9ob00947g

An operationally simple synthesis of activated ynesulfonamides and enesulfonamides is described. Ynesulfonamides can be obtained through reaction of sulfonylamides with activated bromoalkynes and Triton B in a short time at room temperature. Likewise, terminal alkynes react with sulfonylamides to provide enesulfonamides. Z/E enesulfonamides can be transformed exclusively into E enesulfonamides.

Full text of DOI:10.1039/c9ob00947g

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Takeharu Haino et al.
Solvent-induced emission of organogels based on tris(phenylisoxazolyl)
benzene
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DOI: 10.1039/C9OB00947G
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Metal-Free Synthesis of Activated Ynesulfonamides and Teritary
Enesulfonamides
Lucile Andna and Laurence Miesch*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
An operationally simple synthesis of activated ynesulfonamides alkynes is no longer to demonstrate.3 Although
and enesulfonamides is described. Ynesulfonamides can be ynesulfonamides bearing an electron-withdrawing group can
obtained through reaction of sulfonylamides with activated be obtained through elimination of halo-alkenes or -alkynes
1e,1f,4a
bromoalkynes and Triton B in a short time at room temperature. (Scheme 1, a),
as well as through lithiation of the
Likewise, terminal alkynes react with sulfonylamides to provide corresponding terminal ynesulfonamide (Scheme 1, b).4b,4c
enesulfonamides. Z/E enesulfonamides can be transformed
exclusively into E enesulfonamides.
For ynesulfonamides
a) Zhao et al.1e,1f, Anderson et al.4a
Cl
R2
Rapid and reliable methods to synthesize nitrogen-containing
heterocycles exhibiting pharmacological profiles are of utmost
interest. Ynesulfonamides and enesulfonamides are therefore
relevant building blocks for this purpose. Ynesulfonamides are
ynamines bearing an electron-withdrawing group on the
nitrogen atom. Likewise enesulfonamides are electron-
deficient enamines (Fig. 1).
or
Cl
Cl
R2
R1
R2
Cl
Cl
Cl , then R2 +
R1
N
+
base
NH
R2
or
EWG
EWG
or
Cl
50 - 91%
b) Saá et al.4b, Wolf et al.4c
E
1) base
2) E+
Ph
Ph
N
N
R
SO2R2
R
SO2R2
Ts
N
N
Ts
36 - 99%
c)Tam et al.5
R1
Enesulfonamides
n-BuLi, AlCl3
CO2Et
R1
Br
CO2Et
Bn
Bn
NH
Ts
N
1 example, 61%
Ynesulfonamides
Ts
Fig. 1 Ynesulfonamides and enesulfonamides.
d) This work :
EWG2
Triton B
Because of their unusual stability and tunable reactivity,
ynesulfonamides1 and tertiary enesulfonamides2 have become
attractive synthetic tools for the design of many novel
chemical transformations. Consequently, the significance of
these compounds has given rise to the development of
efficient methods for their preparation.
R1
Br
EWG2
NH
R1
N
EWG1
12 examples
51 - 100%
EWG1
For enesulfonamides
e) Gharpure et al.6d, Meyer et al.10
Methods applicable to the synthesis of ynesulfonamides
bearing an electron-withdrawing group are scarce, those that
are performed under transition-metal-free conditions at room
temperature are almost nonexistent. The use of activated
R
CO2R
H
CO2R
R
N
NH
Ts
Ts
NMM : 6 examples, 55 - 91%
DACBO : 1 example, 92%
d) This work :
Triton B
Equipe Synthèse Organique et Phytochimie, Institut de Chimie, CNRS-UdS UMR
7177, 4, rue Blaise Pascal CS 90032, 67081 Strasbourg, France.
E-mail : lmiesch@unistra.fr
Electronic Supplementary Information (ESI) available: Experimental procedures,
synthesis method of starting materials, compound characterization data, 1H and
13C NMR spectra for new compounds. See DOI: 10.1039/x0xx00000x
R
R
EWG2
H
EWG2
NH
N
EWG1
EWG1
15 examples, 53 - 100%
Scheme 1 One-step metal-free syntheses of ynesulfonamides and enesulfonamides.
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A singular example reported by Tam et al., starting from ynesulfonamide 2 was obtained in good yield, without any side
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tosylsulfonamides and bromo-ethylpropiolate, requires the product resulting from double addiDtiOonI: 10o.1n039t/hCe9OBf0o0r9m4e7Gd
use of a strong base such as n- BuLi together with a Lewis acid activated ynesulfonamide (Table 1, entry 8). An aqueous
- conditions that are detrimental to the presence of sensitive solution of basic Triton
B
(benzyltrimethylammonium
functional groups (Scheme 1, c).5
hydroxide) was also investigated. Whereas a catalytic amount
Among other methods,6 tertiary enesulfonamides can be of this base led to poor yields, stoichiometric quantities
obtained via reduction of ynesulfonamides,7 and numerous provided best conditions to obtain exclusively ynesulfonamide
transition
metal-catalyzed
syntheses
of
tertiary 2 (Table 1, entries 9 and 10). The non-basic quaternary
enesulfonamides have also been developed, with either ammonium salt, BTAC, was also tested, but no reaction was
palladium8 or copper catalysts.9 Metal-free syntheses of observed (Table 1, entry 11), thus confirming the necessity of a
tertiary enamides from N-sulfonamides have also been basic medium for this reaction. NMM was investigated, and
reported, although only six examples have been described, all ynesulfonamide 2 could be obtained, but in low yields (Table 1,
of which are restricted to enamides possessing a methyl ester entries 12 and 13). The use of a base is necessary - the
at the  position using NMM. A singular example using DABCO electron-withdrawing effect is not sufficient enough for the
was also reported (Scheme 1, e).6d,10
reaction to take place without it (Table 1, entry 14).
Based on our interest in the reactivity of ynesulfonamides11
Under the optimized conditions the substrate scope was
and enesulfonamides,12 and taking inspiration from our investigated with respect to the amide and the substituent on
previous work on ynesulfonamides under basic conditions,13 the triple bond (Table 2).
we envisaged the synthesis of ynesulfonamides bearing an
electron-withdrawing group by using a base.
Whereas classical ynesulfonamide 2 worked well under
these conditions, it was also possible to obtain
First attempts were conducted with Cs2CO3, with which 24 ynesulfonamides with other protecting groups on the nitrogen
hours were necessary to obtain the desired ynesulfonamide 2 (e.g., nosyl and sulfamoyl groups) that were more easily
in 61% yield (Table 1, entries 1 and 2), although in both cases, deprotected with acceptable yields (compounds 4, 5).
a double Michael addition 3 was observed.14 Heating the Succinimide and butyl derivatives proved to be suitable
reaction mixture under the same conditions did not improve compounds as well (compound 6, 7). Phenyl ketones 8 as well
t
the yield of the reaction (Table 1, entry 3). Switching to BuOK as heterocyclic ketones (compounds 9 and 10) were obtained
led to better yields (Table 1, entries 4 and 5). Yields in the with excellent yields. Whereas ynesulfonamides bearing ,-
same range were observed with NaH (Table 1, entry 6) and unsaturated ketones could not be obtained through a classical
TMG was not beneficial in this case (Table 1, entry 7).
Table 2 Ynesulfonamides synthesis: substrate scope.a
Based on our previous work with quaternary ammoniums
salts,13 we performed the reaction with TBAF. In the event,
Triton B (40 wt. % H2O)
EWG2
Br
EWG2
R1
Table 1 Screening of bases
NH
R1
(1.1 equiv)
N
EWG1
EWG1
THF, rt, 30 min
base (x equiv)
Br CO2Et
(1.1 equiv)
Bn
N
Ts
CO2Et
+
N
Bn
NH
Ts
Bn
Bn
CO2Et
N
Bn
N
Bn
Ts
Conditions
Ts
Bn
Ts
1
2
3
CO2Et
N
CO2Et
N
CO2Et
(2-)Ns
N
S
entry
base
conditions
yields (%) a
O
O
(equiv)
2
-
3
1
100
-
-
-
-
-
-
-
2
6
4
5
, 51%
, 90%
O
, 69%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Cs2CO3 (1.3)
Cs2CO3 (4)
Cs2CO3 (4)
tBuOK (1.3)
tBuOK (1.3)
NaH (1.3)
TMG (1.3)
TBAF c (1.3)
Triton B d (1.3)
Triton B d (0.2)
BTAC e (1.3)
NMM f (1.3)
NMM f (1.3)
-
THF, rt, 2 h
Tol, rt, 24 h
Tol, 85 °C, 16 h
THF, rt, 1 h
MeCN, rt, 1 h
MeCN, rt, 1 h
THF, rt, 19 h
THF, rt, 30 min
THF, rt, 30 min
THF, rt, 6 h
-
18
38
12
-
-
-
-
-
-
-
-
-
Ts
61
28
63
73
65
21
83
90
30
-
Ts
Bn
Ts
O
N
N
CO2Et
N
N
Bu
Ph
O
CO2Et
7
8
, 100%
, 81%
, 50%
Bn
Ts
O
Bn
Ts
O
Bn
Ts
O
N
N
N
-
S
O
50
100
37
52
100
Ph
THF, rt, 19 h
MeCN, rt, 19 h
MeCN, 0 °C, 2 h
THF, rt, 22 h
O
9
10
11
, 84%
, 92%
, 100%
24
37
-
Bn
Ts
O
Bn
Ts
O
Bn
Ts
O
N
N
-
N
N
N
N
a
b
c
Yield of isolated compounds, TMG : 1,1,3,3-Tetramethylguanidine, TBAF :
O
d
O
Tetrabutylammonium fluoride, Triton B : Benzyltrimethylammonium hydroxide
e
f
(40 wt.
%
H2O),
BTAC : Benzyltrimethylammonium chloride, NMM : N-
12
13
14
, 90%
, 57%
, 54%
a Yield of isolated compounds.
methylmorpholine.
2 | J. Name., 2012, 00, 1-3
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copper- catalyzed coupling reaction, Triton B makes it possible In the event, tosylsulfonamide 1 reacted with ethyl propiolate
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to obtain the desired ynesulfonamide quantitatively, thus in the presence of Triton B to providDeOI:t1h0e.10c3o9/rCre9OspBo00n9d4in7Gg
pointing out the efficiency of the method. Ynesulfonamide 11 tertiary enesulfonamide 15/15 ’ quantitatively as an E/Z
could not be obtained in good yields under copper-catalyzed mixture. Sulfamoyl-, mesyl-, and nosyl protecting groups on
conditions in our hands;15 less than a 30% yield was the nitrogen led also to excellent yields of the corresponding
achieved.16 Likewise, Triton B offers a good way to obtain enesulfonamides (compounds 16/16 ’ , 17/17 ’ and 18/18 ’ ).
ynesulfonamides embedded with amides (compound 12, 13). Various substituents on nitrogen atom have been investigated,
To the best of our knowledge, ynesulfonamides bearing and compounds 18/18 ’ , 21/21 ’ and 23 could be obtained.
anamide have not been reported. A Weinreb amide was Notably, palladium-catalyzed coupling approaches failed to
tolerated as well as a substituent on the ynesulfonamide and provide these materials.8a, 8b (S)-4-Phenyloxazolidinone reacted
provided ynesulfonamide 14 in good yield.
under the developed conditions, providing enamides 19/19’. A
Next, we evaluated the possibility to use this strategy to diamide led exclusively to mono tosyl enesulfonamide 22.
synthesize enesulfonamides through the same process by Enesulfonamides substituted with non-enolizable ketones
using activated, terminal alkynes (Table 3).
(compounds 23-25) could be obtained quantitatively with an
exclusive E configuration for the enesulfonamide double bond.
Likewise, terminal alkynes bearing an ,-unsaturated ketone
led to the corresponding dienones 26 and 27 nearly
quantitatively with excellent selectivity. Again, amides are
tolerated in this process (compound 29/29 ’ ) as well as
tosylated enensulfonamide 28/28’.
To our knowledge, among the 15 examples of
enesulfonamides synthesized, 12 compounds are new and
have not been reported in the literature. It should be noticed
that this method is only applicable for the synthesis of
ynesulfonamides and ensesulfonamides bearing an electron-
withdrawing group. Compounds 2, 11, 15 and 25 were
prepared on two grams scale or more without alteration of the
yield, attesting to the performance of the process.
Table 3 Enesulfonamides synthesis: substrate scope.a
Triton B (40 wt. % H2O)
H
EWG2
R
(1.1 equiv)
R
EWG2
NH
N
EWG1
THF, 30 min, rt
EWG1
N
O
Ms
N
CO2Et
Ts
CO2Et
S
CO2Et
N
O
N
Bn
Bn
Bn
17/17'
, 100%
E/Z 72/28
15/15'
, 100%
E/Z 73/27
16/16'
, 88%
E/Z 70/30
O
The mixed E/Z enesulfonamides (15/15 ’, 17/17 ’, 18/18 ’,
20/20 ’, 28/28 ’) could be converted to the pure E compounds
13, 17, 18, 20, 28 by treatment with 20 mol% p-TsOH (Table 4).
Even starting from pure Z isomer 29 ’, we could obtain the E
compound 29 using 50 mol% p-TsOH. Enamides bearing an
ester, amide and tosyl substituents could be transformed by
this method (Table 4).
(4-)Ns
CO2Et
CO2Et
Ts
CO2Et
O
N
N
N
Bn
Ph
18/18'
19/19'
20/20'
, 100%
E/Z 50/50
, 91%
E/Z 75/25
, 53%
E/Z 30/70
Ts
CO2Et
Ts
N
CO2Et
O
Table 4 Isomerization of enesulfonamides.a
N
Ts
O
N
Ph
NH
p-TsOH
(0.2 equiv)
R
EWG2
R
EWG2
N
N
b
21/21'
22
, 74%
E/Z 100/0
23
, 100%
E/Z 100/0
, 62%
CH2Cl2
40 °C, 1 h
EWG1
EWG1
E/Z 50/50
O
O
O
Ts
Ts
Ts
N
Ts
CO2Et
Ms
Bn
CO2Et
(4-)Ns
Bn
CO2Et
N
N
O
Bn
N
N
N
Bn
Bn
Bn
Ph
15
17
18
, 80%
, 80%
, 77%
Ts
24
25
E/Z 100/0
26
, 100%
E/Z 100/0
, 100%
E/Z 100/0
, 100%
O
N
Ts
Ts
CO2Et
Ts
O
O
N
N
N
N
Ts
Ts
Ts
Ts
Bn
N
N
N
Bn
b
Bn
Bn
20
28
29
, 85%
, 83%
, 77%
C3H7
a Yield of isolated compounds. b Starting from pure Z isomer 29’ using 0.5 equiv of
27
28/28'
, 83%
E/Z 35/65
29/29'
, 93%
E/Z 67/33
, 84%
E/Z 100/0
p-TsOH.
a Yield of isolated compounds. b 30% of the starting material was recovered
To explain the formation of either ynesulfonamide or
enesulfonamide, we propose the following mechanism
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Henry, K. Jouvin, G. Karthikeyan, A. Laouiti, MV.ieLwecArotimcletOen,liAne.
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(Scheme 2). After deprotonation of the secondary amide A, a
Michael addition on the activated triple bond takes place to
form the intermediate B. Elimination of bromine provides the
ynesulfonamide C, and protonation leads to the
enesulfonamide D (Scheme 2).
NR4
Triton B
R
R
NH
N
EWG1
EWG1
X
EWG2
A
2
3
M.-X. Wang, Chem. Commun., 2015, 51, 6039 and references
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X
R
EWG2
NR4
B
N
EWG1
Elimination
X = Br
Protonation
X = H
4
EWG2
R
EWG2
R
N
N
EWG1
5
6
K. Villeneuve, N. Riddell and W. Tam, Tetrahedron, 2006, 62,
3823.
EWG1
Scheme 2 Plausible mechanism.
D
C
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In conclusion, robust, simple, metal-free protocols for the
synthesis of ynesulfonamides and enesulfonamides have been
developed. The method can be easily scaled up, and thus gram
scales of ynesulfonamides and enesulfonamides are accessible
at room temperature. Ynesulfonamides and enesulfonamides
difficult to obtain otherwise are accessible with high yields
through this process in a short time without special reaction
conditions. Triton B is critical in avoiding double Michael
addition on the triple bond and promoting the exclusive
formation of ynesulfonamides substituted with esters,
ketones, and amides, and synthetically useful dienones could
be obtained with good to excellent yields. E/Z Mixtures of
enesulfonamides have been converted into the pure E
enesulfonamides. The Triton B approach greatly expands the
availability of ynesulfonamides and enesulfonamides through
its broad application to a variety of diverse amides and
alkynes.
7
8
9
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Conflicts of interest
11 (a) C. F. Heinrich, I. Fabre and L. Miesch, Angew. Chem. Int.
Ed., 2016, 55, 5170; (b) F. Beltran, I. Fabre, I. Ciofini and L.
Miesch, Org. Lett., 2017, 19, 5042.
There are no conflicts to declare.
12 (a) L. Andna and L. Miesch, Org. Lett., 2018, 20, 3430; (b) F.
Beltran and L. Miesch, Org. Lett., 2019, 21, 1569.
13 F. Beltran, L. Andna and L. Miesch, Org. Chem. Front., 2019,
6, 373.
14 (a) S. Nayak, N. Ghosh and A. K. Sahoo, Org. Lett., 2014, 16,
2996; (b) Z. Peng, Z. Zhang, Y. Tu, X. Zeng and J. Zhao, Org.
Lett., 2018, 20, 5688.
Acknowledgements
Support for this work was provided by CNRS and Université de
Strasbourg. L. Andna thanks M.R.T. for a research fellowship.
15 Y. Zhang, R. P. Hsung, M. R. Tracey, K. C. M. Kurtz and E. L.
Vera, Org. Lett., 2004, 6, 1151.
Notes and references
1
For recent reviews on ynesulfonamides synthesis and
chemistry, see: (a) G. Evano, N. Blanchard, G. Compain, A.
4 | J. Name., 2012, 00, 1-3
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16 C. Zhang, L. Chen, K. Chen, C. Wang, Z. Xu, H. Jiang and S.
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DOI: 10.1039/C9OB00947G
Zhu, Org. Chem. Front., 2018, 5, 2510.
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