1478
F. Tamaddon et al. / Catalysis Communications 12 (2011) 1477–1482
CsF-Celite, 50 oC
Solvent-free
2.4. Stability and reactivity of catalyst
R1XH
SO2XR1
+
+
HCl
R
SO2Cl
R
R1= Ar, Alkyl
X = NH, O
A comparison between freshly prepared and stored CsF–Celite in
the tosylation of aniline with TsCl showed that no significant falling of
catalytic activity is occurred, thus the catalyst remains stable whether
kept in a tightly sealed container.
R = Ar, Me
O
O
CsF-Celite (0.5 equiv)
-
HNR1R2
S
NR1R2
+
R
S
O
R
Method A: 120 oC
Method B: Mw
O
2.5. Reusability of the catalyst
O
Scheme 1. CsF–Celite catalyzed sulfonylation and desulfonylation.
The recovered catalyst was regenerated by washing with EtOAc
and drying in an oven under microwave irradiation at 950 W for 300 s.
The recycled catalyst was reused in the tosylation of aniline with no
high decrease in the reaction yield. It is notable that washing the
recovered catalyst by CH3CN resulted in the much leaching of the CsF
and its catalytic activity was decreased significantly.
acetonitrile, filtered and washed with acetonitrile (3×2.5 ml) [29].
The impregnated CsF–Celite was further dried under vacuum or using
microwave irradiation at 950 W for two consequent 60 s and kept in a
desiccator. The conditions of preparation had critical effects on the
properties of CsF–Celite.
2.6. Representative data for the selected compounds
2.2. General procedure for sulfonylation of alcohols and amines
2.6.1. N-Phenyl-p-toluenesulfonamide (Table 2, entry 1a)
White needles (EtOH:H2O), 93% yield. IR (KBr); ν=3251, 1375,
1158, 757, and 685 cm−1. 1H NMR (250 MHz, DMSO-d6): δ 2.37 (s, 3H,
CH3), 6.60 (s, 1H, NH), 7.03–7.15 (m, 2H), 7.33 (s, 5H), 7.62–766 (m,
2H) ppm. 13C NMR (62.5 MHz, CDCl3) δ: 117.38, 117.63, 123.36,
124.48, 126.20, 126.88, 127.88, 128.32, 128.55, 128.96, 130.60, 130.84,
145.48, and 147.93. EIMS (probe) 70 eV, m/z (rel. int.): 358, 281
(100), 252, 167, 149, and 57.
CsF–Celite (0.3 mmol per NH or OH group) was added to a mixture
of substrate (3 mmol) and sulfonyl chloride (3 mmol). The reaction
mixture was then stirred at 50 °C and the progress of the reaction was
followed by TLC. After completion of the reaction, the mixture was
diluted with EtOAc and filtered to remove the catalyst. The organic
layer was washed with 10% NaHCO3 and brine and dried over
anhydrous Na2SO4. Evaporation of the solvent gave the desired
product. In some cases of O-sulfonylation reactions, products were
purified by short column chromatography.
2.6.2. N-Butyl-benzenesulfonamide (Table 2, entry 3b)
White needles (EtOH:H2O), 94% yield, Mp=83 °C (lit. 85 °C [32]).
The structure of products was assigned by analysis of their IR, 1H
NMR, 13C NMR spectra and comparison to authentic samples or
elemental analysis. Known products showed physical states; melting
points and spectroscopic data in agree with authentic samples.
IR (KBr); ν=3240, 1338, 1168, and 920 cm−1 1H NMR (250 MHz,
.
CDCl3): δ 0.91 (t, 3H, CH3), 1.10–1.50 (m, 4H, 2×CH2), 2.90 (m, 2H,
CH2), 5.10 (br s, 1H, NH), 7.30–7.50 (m, 2H), 7.80–8.02 (m, 2H) ppm.
2.6.3. N-Glycyl-p-toluenesulfonamide (Table 2, entry 8a)
White needles (EtOH), 91% yield, Mp=170 °C (lit. 171 °C [31]). IR
(KBr); ν=3356, 1713, 1137, 1149, and 918 cm−1. 1H NMR (250 MHz,
DMSO-d6): δ 2.42 (s, 3H, CH3), 3.58 (d, J=6 Hz, 2H, CH2), 6.71 (br s,
1H, NH), 7.20 (d, J=7.8 Hz, 2H), 7.36 (d, J=7.8 Hz, 2H), 7.7 (br s, 1H,
OH) ppm.
2.3. General procedure for deprotection of sulfonamides
A mixture of CsF–Celite (1.5 mmol) and substrate (3 mmol) was
stirred at 120 °C (or irradiated by the microwave under solvent-free
conditions or refluxed in acetonitrile or CF3CH2OH). After completion
the reaction (TLC monitoring), EtOAc (10 ml) was added and filtered
to remove the catalyst. Then water was added and the organic layer
was separated and washed with 10% NaHCO3 and brine. The
combined organic layer was dried over Na2SO4, the EtOAc was
removed at reduced pressure to give the desired product.
2.6.4. Methyl-benzenesulfonate (Table 2, entry 9)
Thick oil, 92% yield. IR (KBr); ν=3058, 2957, 1566, 1479, 1361,
1188, 757, and 685 cm−1 1H NMR (250 MHz, CDCl3): δ 3.70 (s, 3H,
.
CH3), 7.40–7.70 (m, 3H), 7.80 (d, 2H) ppm. 13C NMR (62.5 MHz,
Table 1
Tosylation of aniline and butanol.a
Catalyst
RXH + H3C
RXTs + HCl
SO2Cl
neat or CH3CN
Entry
RXH
Catalyst/temp (°C)
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
Aniline
Aniline
Aniline
Aniline
Aniline
Aniline
Aniline
Aniline
Aniline
Aniline
Aniline
n-Butanol
n-Butanol
CsF (0.152 g, 1 mmol)/50
Celite (1 g)/50
CsF–Celite (0.38 g, 30 mol%)/50
CsF–Celite (0.38 g, 30 mol%)c/50
CsF–Celite (0.57 g, 0.5 equiv)/50
CsF–Celite (0.57 g)/100
8
2
70
78
96
95
78
0.6
0.6
0.75
3
2.5
2
0.033
0.045
0.090
3
d
–
d
CsF–Celite (0.57 g)/110
–
CsF–Celite (0.57 g)c/120
CsF–Celite (1.15 g, 1 equiv)c/MW
CsF–Celite (1.15 g)c/CH3CN/MW
KF/Alumina (2 equiv)/MW [7]
Celite (1 g)/50
–
d
d
9
–
d
10
11
12
13
–
d
–
60
92
CsF–Celite (30 mol%)c/50
2
a
The reactions were carried out in 1 mmol scale under the solvent-free condition.
Isolated yield.
CsF–Celite was prepared by microwave irradiation.
Sulfonylation was completed but subsequently desulfonylation was occurred.
b
c
d