A simple method for the preparation of N-sulfonylimines by direct condensation of p-toluenesulfonamide with diaryl ketones

Article abstract of DOI:10.1081/SCC-100103318

Diaryl ketones condense with p-toluenesulfonamide in refluxing 1,2-dichloroethane in the presence of TiCl₄/ Ti(O-iPr)₄ or TiCl₄/Et₃N to give N-sulfonylimines in generally good yields.

Full text of DOI:10.1081/SCC-100103318

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A SIMPLE METHOD FOR
THE PREPARATION OF N-
SULFONYLIMINES BY DIRECT
CONDENSATION OF p-
TOLUENESULFONAMIDE WITH
DIARYL KETONES
a
a
Ram N. Ram & Arif Ali Khan
a
Department of Chemistry, Indian Institute of
Technology, Delhi, Hauz Khas, New Delhi, 110016,
India
Published online: 09 Nov 2006.
To cite this article: Ram N. Ram & Arif Ali Khan (2001) A SIMPLE METHOD FOR
THE PREPARATION OF N-SULFONYLIMINES BY DIRECT CONDENSATION OF p-
TOLUENESULFONAMIDE WITH DIARYL KETONES, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry,
31:6, 841-846, DOI: 10.1081/SCC-100103318
To link to this article: http://dx.doi.org/10.1081/SCC-100103318
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SYNTHETIC COMMUNICATIONS, 31(6), 841–846 (2001)
A SIMPLE METHOD FOR THE
PREPARATION OF N-SULFONYLIMINES
BY DIRECT CONDENSATION OF
p-TOLUENESULFONAMIDE WITH
DIARYL KETONES
Ram N. Ram* and Arif Ali Khan
Department of Chemistry, Indian Institute of Technology,
Delhi, Hauz Khas, New Delhi-110016, India
ABSTRACT
Diaryl ketones condense with p-toluenesulfonamide
in refluxing 1,2-dichloroethane in the presence of TiCl4/
Ti(O-iPr) or TiCl /Et N to give N-sulfonylimines in generally
4
4
3
good yields.
N-sulfonylimines are useful precursors for the preparation of
1
important synthetic intermediates such as oxaziridines and aziridines, as
2
3
well as for the synthesis of compounds of medicinal importance. N-sulfo-
,4
nylimines also serve as heterodienes and heterodienophiles in [4 þ 2]
5
cycloaddition reactions. Direct condensation of primary sulfonamides
with aldehydes in the presence of some dehydrating agents (TiCl , 4-A
4
1
,6–10
Molecular sieves, MgSO , AlCl ) is documented in the literature.
4
3
However, to the best of our knowledge, only a few reports are available
*
Corresponding author. E-mail: rnram@chemistry.iitd.ernet.in
41
8
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

8
42
RAM AND KHAN
for the preparation of N-sulfonylimines of hindered non-enolizable ketones.
None of these methods involves direct condensation of sulfonamides with
diaryl ketones. The N-sulfonylimines of such ketones have been prepared
1
1
by in situ generation of their oxime O-sulfinyl derivatives and their
subsequent homolytic rearrangement to sulfonylimines by the reaction of
1
2
p-toluenesulfonamide–AlCl3 complex with Ph CCl in dichloroethane,
2
2
and by the reaction of a few diaryldiazomethanes with N,N-dichloroarene-
1
3,14
sulfonamides or with chloramine B or chloramine T.
Herein, we report
two simple methods for the direct condensation of p-toluenesulfonamide
with diaryl ketones affording N-sulfonylimines in generally good to excellent
yields.
In Method I, equimolar proportions of p-toluenesulfonamide and
ketone are heated at reflux for 15–20h in dichloroethane in the presence
of a mixture of TiCl and Ti(O-iPr) , taken in 0.5 and 0.2–0.3 molar pro-
4
4
portions, respectively, giving N-sulfonylimines in moderate to good yields
35–76%).
In Method II, the reactants in the molar ratio as given by equation (1)
(
are heated at reflux for 3–5 h in dichloroethane. This method is superior to
the first, as the reaction time is only 3–5 h, giving the products in higher
1
yields (71–97%) (Table 1).
5
Equation 1
These methods also worked well with aromatic aldehydes; however,
enolizable ketones gave a number of unidentified products. These reactions
have been carried out in different solvents (e.g., benzene, chloroform,
carbon tetrachloride and a mixture (1:1) of CHCl and CCl ). In all these
3
4
cases the N-sulfonylimines obtained were in syrupy form and took 15–30
days to crystallize. However, these compounds were obtained as solids after
final work-up when prepared by Method II using 1,2-dichloroethane as the
reaction medium, and can easily be recrystallized from a suitable solvent. All
1
13
the N-sulfonylimines were characterized by H and C NMR, mass and IR
spectral studies.

N-SULFONYLIMINES
Table 1. Synthesis of N-Sulfonylimines from Diary1 Ketones
843
Reflux Time
h)
Yield of
N-Sulfonylimine (%)
(
S.No.
Ketone
Method I
Method II
Method I
Method II
a
1
2
3
4
5
6
7
8
R ¼ H
20
15
15
15
17
205
17
18
5
3
3
4.5
3
76
61
6071
56
83
73
¼ Br
¼ OMe
¼ Me
¼ NO
¼ Ph
73
83
2
62
70 97
b
Chalcone
9-Fluorenone
4.5
5
35
52
75
82
b
a
See equation 1.
b
In this method, the reaction developed a dark brown color, which was removed by
treatment with animal charcoal, resulting in lower yields.
EXPERIMENTAL
1
6
Melting points are uncorrected. p-Nitrobenzophenone
and
1
7
Ti(O-iPr)4 were prepared by the reported procedures. All the other
reagents were commercially available and were used as received except
triethyl amine, which was dried before use by heating at reflux over calcium
hydride for 2 h and distilled. The solvents were freshly distilled before use.
IR spectra were recorded as KBr discs using a Nicolet 460FT-IR spectro-
photometer and NMR spectra were recorded in CDCl3 on a Brucker
300 MHz DPX spectrometer with TMS as the internal standard. Mass spec-
tra were recorded on Jeol SX-102 spectrometer at RSIC, CDRI Lucknow.
General Procedure
Method I
Diaryl ketone (5 mmol) and p-toluenesulfonamide (5 mmol) were dis-
solved in freshly distilled 1,2-dichloroethane (20mL). To this solution TiCl 4
(
2.5 mmol) and Ti(O-iPr) (1.50mmol) were successively added. The reac-
4
tion mixture was heated at reflux for 15–20h. After completion of the
reaction (marked by a single spot of N-sulfonylimine on TLC), the reaction
mixture was cooled to room temperature and then washed with dil. HCl,

8
44
RAM AND KHAN
followed by saturated NaHCO and water. The dichloroethane solution was
3
dried (anhydrous Na SO ) and evaporated on a rotary evaporator to
2
4
give light yellow/brown syrup, which solidified on standing at room
temperature for 15–30days. The solid N-sulfonylimines were further
purified by recrystallization.
Method II
p-Toluenesulfonamide (5 mmol) and ketone (5 mmol) were dissolved
in dichloroethane and TiCl (2.5 mmol) was added with stirring, followed by
4
dropwise addition of triethyl amine (10mmol). The reaction mixture was
heated at reflux for 3–5 h. The progress of the reaction was monitored
by TLC. Usual work-up after the completion of the reaction yielded
N-sulfonylimines in high yields.
Analytical and Spectral Data of N-Sulfonylimines (1–8)
11
ꢀ ꢀ ꢀ
1
: Colorless crystals (benzene) m.p. 102 –104 C (lit., 102 C); IR
ꢁ
À1
(
7
1
cm ) ꢀ
1601, ꢀ
1318(asym), 1158(sym); H: 2.43 (3H, s, CH ),
3
C ¼ N
O ¼ S ¼ O
ꢁ
.25–7.83 (14H, m, aromatic); C: 21.45 (CH ), 127.26, 128.04, 129.28,
3
þ
29.64, 138.56, 143.23 (aromatic), 178.65 (C ¼ N); m/z: 335 (M , 20%),
(
calc. 335.42), 272 (27%), 180 (100%), 155 (23%).
ꢀ
ꢀ
À1
2
586, ꢀ
: Colorless crystals (dichloroethane) m.p. 98 –100 C; IR (cm ) ꢀ
ꢁ
C ¼ N
1
m, aromatic); C: 21.48 (CH ), 127.27, 128.18, 129.35, 131.40, 138.29, 143.45
1325(asym), 1154(sym); H: 2.43 (3H, s, CH ), 7.25–7.83 (13H,
3
O ¼ S ¼ O
ꢁ
3
þ
(
4
aromatic), 177.37 (C ¼ N); m/z: 415, 413 (M , 54%, 58%), (calc. 413.32,
15.32), 351, 349 (33%, 46%), 259, 257 (59%, 54%), 155 (49%).
3
ꢀ
ꢀ
À1
: Light yellow crystals (dichloroethane) m.p. 94 –96 C; IR (cm )
ꢁ
ꢀ
(
(
1594, ꢀ
1303(asym), 1151(sym); H: 2.43 (3H, s, CH ), 3.86
3
C ¼ N
O ¼ S ¼ O
ꢁ
3H, s, -OCH ), 6.87–7.83 (13H, m, aromatic); C: 21.42 (CH ), 55.43
3 3
OCH ), 113.61, 126.31, 126.67, 127.11, 127.81, 129.21, 129.49, 130.87,
3
1
3
32.74, 136.42, 138.80, 143.00, 143.18 (aromatic), 178.08 (C ¼ N); m/z:
þ
65 (M , 72%), (calc. 365.45), 301 (11%), 210 (100%), 155 (5%).
4
ꢀ
ꢀ
À1
: Light yellow crystals (dichloroethane) m.p. 82 –84 C; IR (cm )
ꢁ
ꢀ
7
1
7
1585, ꢀ
.19–7.84 (13H, m, aromatic); C: 21.44, 21.55 (2CH ), 127.21, 127.93,
1326(asym), 1154(sym); H: 2.41, 2.42 (6H, 2CH ),
3
C ¼ N
O ¼ S ¼ O
ꢁ
3
þ
28.83, 129.24, 138.78, 143.11 (aromatic), 178.74 (C ¼ N); m/z: 349 (M ,
4%), (calc. 349.45), 285 (38%), 194 (91%), 155 (35%).
ꢀ ꢀ
À1
5
593, ꢀ
: Yellow crystals (ethyl acetate) m.p. 137 –138 C; IR (cm ) ꢀ
ꢁ
C ¼ N
1
1324(asym), 1151(sym); H: 2.45 (3H, s, CH ), 7.25–7.85
3
O ¼ S ¼ O

N-SULFONYLIMINES
845
ꢁ
13H, m, aromatic); C: 21.51 (CH ), 123.15, 127.33, 128.56, 129.50, 129.99,
(
3
þ
1
33.95, 137.74, 143.95 (aromatic), 175.81 (C ¼ N); m/z: 380(M , 21%),
(
calc. 380.42), 316 (8%), 225 (14%), 155 (64%).
6
ꢀ
ꢀ
À1
: Yellow crystals (benzene) m.p. 108 –111 C; IR (cm ) ꢀ
ꢁ
1612,
C ¼ N
ꢀ
aromatic); C: 21.47 (CH ), 126.70, 127.16, 127.28, 128.05, 128.17, 128.89,
1306(asym), 1148(sym); H: 2.43 (3H, s, CH ), 7.25–7.85 (18H, m,
3
O ¼ S ¼ O
ꢁ
3
1
29.30, 130.61, 138.63, 139.72, 143.22 (aromatic), 178.36 (C ¼ N); m/z: 411
þ
(
M , 100%), (calc. 411.52), 347 (17%), 256 (70%), 155 (11%).
ꢀ
ꢀ
11
7
52 –153 C); IR (cm ) ꢀ
: Light yellow crystals (ethyl acetate) m.p. 150 –152 C (lit.,
ꢀ
ꢀ
À1
1
1612, ꢀ
H: 2.41 (3H, s, CH ), 7.03–8.00 (16H, m, aromatic and alkenic); C: 21.47
1314(asym), 1146(sym);
ꢁ
C ¼ N
O ¼ S ¼ O
ꢁ
3
(
CH ), 127.15, 128.29, 128.66, 128.98, 129.37, 129.99, 131.00, 131.76, 134.56,
3
1
38.77, 143.36, 148.66 (alkenic and aromatic), 177.51 (C ¼ N); m/z: 361
þ
(
M , 8%), (calc. 361.46), 206 (100%), 204 (69%).
ꢀ ꢀ
16
8
84 –186 C); IR (cm ) ꢀ
:
Orange needles (dichloroethane) m.p. 182 –184 C (lit.,
À1
ꢀ
ꢀ
1
1607, ꢀ
H: 2.46 (3H, s, CH ), 7.45–8.01 (12H, m, aromatic); C: 21.50(CH ),
1316(asym), 1151(sym);
ꢁ
C ¼ N
O ¼ S ¼ O
ꢁ
3
3
1
1
20.15, 126.54, 126.97, 128.76, 129.38, 134.67, 138.88, 143.46 (aromatic),
þ
72.36 (C ¼ N); m/z: 333 (M , 38%), (calc. 333.40), 269 (28%), 177
(
13%), 155 (39%).
ACKNOWLEDGMENTS
The authors are thankful to DST and CSIR—New Delhi for financial
assistance.
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1
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Received in Japan April 3, 2000