An easy synthesis of aliphatic and aromatic N-sulfonyl aldimines

Article abstract of DOI:10.1055/s-2000-6232

N-Arenesulfonyl aldimines were prepared from aliphatic and aromatic aldehydes in a two-step transformation.

Full text of DOI:10.1055/s-2000-6232

SHORT PAPER
75
An Easy Synthesis of Aliphatic and Aromatic N-Sulfonyl Aldimines
Fabrice Chemla,* Virginie Hebbe, Jean-F. Normant
Laboratoire de Chimie des Organo-Eléments, URA 473 CNRS, Université Pierre et Marie Curie, 4, Place Jussieu, Tour 44-45, 2e étage,
Boîte 183, 75252 Paris Cedex 05, France
Fax: +33(01)44277567; E-mail: fchemla@ccr.jussieu.fr
Received 27 July 1999
pounds 1 during the reaction (in a two-phase system for
Abstract: N-Arenesulfonyl aldimines were prepared from aliphatic
example, or by simple extraction of the precipitate at the
and aromatic aldehydes in a two-step transformation.
end of the reaction) led only to the sulfonamide recovery.
Furthermore, we were unable to purify these compounds
Key words: imines, sulfonamides, sulfones
by chromatography. Finally, we engaged them in the next
step without any purification, except for a simple wash
with pentane.
The aldimine moiety has been widely used in organic syn-
thesis.1 Its reactivity has been shown to be lower than that
of the parent aldehyde, and a number of activating groups
on nitrogen have been used to enhance this reactivity.
Among these activating groups, the sulfonyl moiety has
been found to be very effective. Sulfonylimines derived
from aromatic aldehydes (or aliphatic aldehydes bearing
no enolizable α-hydrogen) are very easy to prepare, for
example by the reaction of the corresponding aldehyde
with sulfonamides (in the presence of a Lewis acid2 or a
Brönsted acid3), with N-sulfinyl sulfonamides4 or sulfonyl
isocyanate;5 with tellurilimines6 or bismuthimines;7 they
can also be prepared from the corresponding N-
trimethylsilylimines8 or oximes,9 by oxidation of the cor-
responding sulfenylimine or from the corresponding alde-
hyde acetal.10 By contrast, sulfonylimines derived from
aliphatic aldehydes are much more difficult to prepare,
presumably due to their high reactivity. They can be pre-
pared by photolysis;11 or in situ by reaction of the corre-
sponding aliphatic aldehyde12 with N-sulfinyl-p-
toluenesulfonamide; or the corresponding aliphatic alde-
hyde dimethylacetal13 with an arenesulfonamide, both in
the presence of a Lewis acid. This is problematic when
these imines have to be used in reactions, which are not
compatible with the presence of a Lewis acid. We would
like to report here a new, easy and practical synthesis of
sulfonylimines derived from either aliphatic or aromatic
aldehydes.
HCOOH
H2O
NHSO2Ar
SO2p-Tol
RCHO + p-TolSO2Na + ArSO2NH2
R
1
SO2Ar
NaHCO3
N
R
H
H2O / CH2Cl2
2
Scheme 1
The second step was more complicated. Treatment of
compounds 1 with a base yielded the desired sulfo-
nylimines, but fine variations of the base strength were
necessary. Treatment with aq 10% NaOH gave the corre-
sponding imine, albeit in low yield, reaction of 1 with
DBU, as well as with potassium carbonate in refluxing
THF14 gave only decomposition materials. Finally, we
found that a simple treatment with aq sodium hydrogen-
carbonate or carbonate at r.t. was efficient, and we could
then obtain the corresponding imines 2 in a good overall
yield.
The reaction is very general. As shown in Table 1, benz-
enesulfonyl- or p-toluenesulfonylimines derived from
simple aliphatic aldehydes (entry 1-6, 8-10), as well as
from aromatic aldehydes (entry 7) were obtained. In all
cases, the sulfonylimines were obtained as one geometri-
cal isomer (presumably E). The obtained sulfonylimines
were found to be relatively stable over a two-day period at
0 °C, except for the imines 2i and 2j. Imine 2j was espe-
cially unstable, decomposing within one hour, and very
unstable in chloroform. For these reasons, we were
obliged to design a special operatory mode for preparing
this imine.
Recently, A. Greene and co-workers14 have disclosed an
original approach for the synthesis of the t-butyl N-(ben-
zylidene)carbamate through a sulfonamidosulfone pre-
pared by a method described by Strating.15 We wondered
whether this method could be applicable for the synthesis
of sulfonyl aldimines derived from aliphatic enolizable al-
dehydes, which have never been described previously.
The condensation of aldehydes, sulfonamides and arene-
sulfinic acid to the corresponding sulfonamide sulfone of
the type 1 (Scheme 1) was described previously by Strat-
ing. However, this showed to be troublesome. In order to
achieve good yields, the condensation must be carried out
in water. We also obtained some evidence for an equilib-
rium process, as all our attempts for extracting com-
No reaction was observed with cyclohexanone and with
pivalaldehyde. On the other hand, in the case of a,b-unsat-
urated aldehydes (cinnamaldehyde and crotonaldehyde),
under standard conditions we obtained only the 3-sulfonyl
Synthesis 2000, No. 1, 75–77 ISSN 0039-7881 © Thieme Stuttgart · New York

76
F. Chemla et al.
SHORT PAPER
Table 1 Preparation of N-Sulfonylimines (2a–2j) from Aldehydes
Imines 2a-i; General Procedure
A mixture of aldehyde (10 mmol), arenesulfonamide (10 mmol) and
sodium p-toluenesulfinate (1.78 g, 10 mmol) or sodium benzenesul-
finate (1.82 g, 11 mmol) in formic acid (15 mL) and H2O (15 mL)
was stirred for 12 h at r.t. The resulting white precipitate was
filtered off, washed with H2O (2 x 10 mL), then pentane (10 mL),
and dissolved in CH2Cl2 (100 mL). Sat. aq NaHCO3 or Na2CO3 (70
mL) was added and the solution was well stirred for 2 h at r.t. The
organic phase was decanted, the aqueous phase extracted with
CH2Cl2 (70 mL) and the combined organic layers dried (NaHCO3),
filtered off and the solvent removed under vacuum to yield the cor-
responding sulfonylimine 2a-i (Table 2).
Entry Aldehyde
N-Sulfonylimine
Yield (%)
2a 66
1
2
3
n-BuCHO
n-BuCHO
2b 78
2c 74
N-Ethylidene 4-methylbenzenesulfonamide 2j
4
2d 76
A mixture of acetaldehyde (440 mg, 10 mmol), p-toluenesulfonam-
ide (1.72 g, 10 mmol) and sodium benzenesulfinate (1.82g,
11mmol) in formic acid (15 mL) and H2O (20 mL) was stirred for
12 h at r.t. The resulting white precipitate was filtered off, washed
with pentane (10 mL) and dissolved in CH2Cl2 (100 mL). The solu-
tion was washed rapidly with a sat. aq NaHCO3 (70 mL). The or-
ganic phase was decanted, the aqueous phase extracted with CH2Cl2
(70 mL) and the combined organic layers dried rapidly (NaHCO3),
filtered off and the solvent removed under vacuum to yield sul-
fonylimine 2j (Table 2).
5
6
7
i-PrCHO
i-PrCHO
PhCHO
2e 55
2f 49
2g 63
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10
MeCHO
2j 41
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aldehyde 3 derived from the 1,4-addition product of
sulfinic acid (Scheme 2). Further reaction with 3 in the
same reaction conditions gave the corresponding sulfona-
midosulfone in low yield, presumably due to the low sol-
ubility of compound 3.
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O
p-TolSO2Na
p-TolSO2
R
O
R
H
p-TolSO2NH2
HCOOH / H2O
H
R = Ph, Me
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3
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Scheme 2
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In conclusion, we have disclosed a new, practical and ef-
ficient synthesis of N-sulfonylimines derived from ali-
phatic or aromatic aldehydes. These N-sulfonylimines can
then be engaged in further reactions which are not com-
patible with the conditions used for preparing these imines
in situ (e.g. acidic conditions). Further studies in this area
will be reported in due course.
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Synthesis 2000, No. 1, 75–77 ISSN 0039-7881 © Thieme Stuttgart · New York

SHORT PAPER
An Easy Synthesis of Aliphatic and Aromatic N-Sulfonyl Aldimines
77
Table 2 Selected data for N-Sulfonylimines 2a–j
Entry
1
N-Sulfonylimine
1H NMR (400MHz, CDCl3/TMS)
d, J (Hz)
13C NMR (100MHz, CDCl3/TMS)
d
IR (KBr, Nujol)
cm–1
2a
0.89 (t, 3 H, J = 7.2), 1.35 (m, 2 H), 1.58 (m, 13.68, 22.20, 26.62, 35.71, 126.36,
2 H), 2.52 (dt, 2 H, J = 7.6, 4.6), 7.50–7.70 129.0, 135.64, 179.28
(m, 3 H), 7.90 (d, 2 H, J = 8.4), 8.63 (t, 1 H,
1630, 1590, 1450,
1380, 1330, 1170,
1100, 750, 690
J = 4.4)
2
2ba
0.91 (t, 3 H, J = 7.2), 1.37 (m, 2 H), 1.62 (m, 13.70, 21.65, 22.22, 26.66, 35.65,
2 H), 2.45 (s, 3 H), 2.53 (m, 2 H), 7.34 (d, 128.11, 129.66, 134.60, 144.71,
2 H, J = 7.9), 7.80 (dd, 2 H, J = 8.1), 8.6 (t, 178.61
1 H, J = 4.8)
1630, 1590, 1450,
1370, 1320, 1150,
1080, 800
3
4
5
6
7
2cb
2dc
2ed
2fe
1.10–1.35 (m, 5 H), 1.60–2.00 (m, 5 H),
2.40 (m, 1 H), 7.57–7.67 (m, 3 H), 7.90 (dd, 129.54, 133.97, 138.24, 178.08
2 H, J = 8.0), 8.50 (d, 1 H, J = 4.4)
25.46, 28.73, 25.98, 44.14, 128.39,
1625, 1580, 1450,
1370, 1315, 1170,
1090, 750, 690
1.16–1.35 (m, 5 H), 1.65–1.95 (m, 5 H),
2.44 (m, 4 H), 7.33 (d, 2 H, J = 8.2), 7.80 (d, 128.05, 129.66, 134.76, 144.61,
2 H, J = 8.3), 8.49 (d, 1 H, J = 4.5) 181.09
21.65, 25.08, 28.34, 25.60, 43.66,
1630, 1600, 1450,
1380, 1310, 1160,
1090, 800
1.16 (d, 6 H, J = 7.2), 2.7 (m, 1 H), 7.40– 18.35, 35.14, 126.76–129.57, 134.05, 1625, 1590, 1450,
7.80 (m, 3 H), 7.92 (d, 2 H, J = 7.3), 8.51 182.93
(d,1 H, J = 4.0)
1380, 1330, 1160,
1090, 730, 690
1.21 (d, 6 H, J = 7.2), 2.40 (s, 3 H), 2.72
(hept, 1 H, J = 2.6), 7.31 (d, 2 H, J = 8.2), 129.68, 134.69, 144.68, 181.90
7.80 (d, 2 H, J = 8.3), 8.50 (d, 1 H, J = 4.2)
17.99, 21.52, 21.66, 34.68, 128.10,
1630, 1600, 1460,
1310, 1160, 1090, 820
2gf
2.46 (s, 3H), 7.36 (d, 2H, J=8.3), 7.51 (t,
21.0, 128.1–129.8, 131.3, 134.9, 144.6, 1650, 1600, 1570,
2H, J=7.8), 7.64 (t, 1H, J=7.9), 7.90–7.96 170.1
(m, 4H), 9.05 (s, 1H)
1450, 1380, 1320,
1160, 1090, 820, 760,
690
8
9
2h
2if
0.71 (d, 6 H, J = 6.5), 1.72 (m, 1 H), 1.92 21.13, 22.21, 25.49, 44.05, 127.50,
(bs, 2 H), 2.00 (s, 3 H), 6.92 (m, 2 H), 8.00 127.98, 129.83, 136.19, 144.29,
1630, 1600, 1470,
1330, 1170, 1095, 820
(m, 2 H), 8.60 (t, 1 H, J = 5.0)
177.63
1.23 (d, 3 H, J = 7.3), 1.90 (s, 3 H), 3.28 (dq, 16.48, 20.55, 45.15, 127.20–128.71,
1 H, J = 7, 41), 6.70–7.20 (m, 6 H), 7.93 (d, 135.23, 138.71, 143.91, 177.85
1 H, J = 8.0), 7.99 (d, 2 H, J = 8.1), 8.77
1630, 1600, 1490,
1450, 1400, 1330,
1170, 1090, 920, 820,
760, 680
(d, 1 H, J = 4.0)
10
2jf
1.33 (d, 3 H, J = 5.1), 1.91 (s, 3 H), 6.80 (d, 21.16, 21.76, 128.29, 129.87,
2 H, J = 8.2), 8.02 (d, 2 H, J = 8.2), 8.32 (q, 135.60, 144.48, 175.18
1 H, J = 5.0)
1625, 1590, 1450,
1320, 1150, 1090, 810
a Anal. Calcd for C12H17NO2S: C, 60.22, H, 7.16, N, 5.85. Found: C, 60.13; H, 7.30; N, 5.90.
b Anal. Calcd for C13H17NO2S: C, 62.12, H, 6.82, N, 5.57. Found: C, 62.15, H, 7.10, N, 5.29.
c Mp: 106°C, Anal. Calcd for C14H19NO2S: C, 63.36, H, 7.22, N, 5.28. Found: C, 62.99, H, 7.27, N, 5.26.
d Anal. Calcd for C10H13NO2S: C, 56.85, H, 6.20, N, 6.63. Found: C, 56.88, H, 6.29, N, 6.50.
e Mp: 82°C, Anal. Calcd for C11H15NO2S: C, 58.64, H, 6.71, N, 6.22. Found: C, 58.61, H 6.81, N, 6.16.
f Mp: 116 °C, Anal. Calcd for C14H13NO2S: C, 64.84; H, 5.05; N, 5.40. Found: C, 64.65; H, 5.75; N, 5.50
g NMR measured using C6D6 as solvent.
(13) Ishatani, H.; Nagayama, S.; Kobayashi, S. J. Org. Chem.
Article Identifier:
1437-210X,E;2000,0,01,0075,0077,ftx,en;P04399SS.pdf
1996, 61, 1902.
(14) Kanazawa, A. M.; Denis, J. N.; Greene, A. E. J. Org. Chem.
1994, 59, 1238.
(15) Engberts, J. B. F. N.; Strating, J. Recl. Trav. Chim. 1965, 84,
942.
Synthesis 2000, No. 1, 75–77 ISSN 0039-7881 © Thieme Stuttgart · New Yorkk