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Vol. 61, No. 4
Table 4. Oxidation of Several Dithioacetals with 30% H2O2 Catalyzed
by NbCl5
using a Jasco IR-8300 FT-IR spectrophotometer. The mass
spectra were recorded on a Shimadzu GCMS-QP1100EX
spectrometer.
Oxidation of Dithioacetals to Bissulfonylmethylenes;
General Procedure To a stirred solution of a dithioacetal
(1mmol) in methanol (6mL) was added niobium(V) chlo-
ride (27mg, 0.1mmol) and 30% hydrogen peroxide (1.6mL,
16.0mmol), then the mixture was stirred at r.t. The reaction
was monitored by TLC. After the dithioacetal disappeared
from the TLC, sat. aq. sodium thiosulfate (20mL) was added,
and the resulting mixture was extracted with dichloromethane
(20mL×2). The extract was dried over anhydrous magnesium
sulfate. The solvent was evaporated, and the residue was puri-
fied by silica gel column chromatography (hexane–EtOAc) to
afford the 1,3-bissulfonylmethylenes.
Entry
1
Product
Time
Yield (%)
2h
95
(sulfonal)
2
3
9h 30min
3h
86
72
2-Methyl-2-naphthalen-2-yl-[1,3]dithiane 1,1,3,3-Tetra-
oxide Colorless crystals; mp 182–183°C. 1H-NMR (CDCl3) δ:
2.25 (3H, s), 2.31–2.42 (1H, m), 2.51–2.57 (1H, m), 3.20–3.28
(2H, m), 3.57–3.62 (1H, m), 3.76–3.84 (1H, m), 7.56–7.62
(2H, m), 7.95–7.98 (1H, m), 8.01–8.05 (3H, m), 8.40 (1H, s).
13C-NMR (CDCl3) δ: 10.71, 16.93, 46.35, 46.41, 82.38, 126.62,
127.03, 127.20, 127.45, 127.48, 127.83, 128.65, 131.25, 132.99,
133.56. IR (KBr) cm−1: 1559, 1314, 1136, 1056. MS (m/z): 324
(M+). HR-MS Calcd for C15H17O4S2 (M++H): 325.0568. Found:
325.0559.
4
5
1h 10min
2h 15min
98
85
2,2-Bis(ethanesulfonyl)propane
(Sulfonal)6) Colorless
crystals; mp 126–128°C (lit.6) 124–125°C). 1H-NMR (ace-
tone-d6) δ: 1.37 (6H, t, J=7.5Hz), 1.76 (6H, s), 3.47 (4H, q,
J=7.5Hz). 13-C-NMR (acetone-d6) δ: 4.44, 16.22, 43.91, 81.16.
IR (neat) cm−1: 3425, 1633, 1304, 1107. MS (m/z): 228 (M+),
135, 95, 77, 59.
1,1-Bis(ethanesulfonyl)ethane6) Colorless crystals; mp
1
75–76°C (lit.6) 74–75°C). H-NMR (acetone-d6) δ: 1.37 (6H,
t, J=7.3Hz), 1.77 (3H, d, J=7.3Hz), 3.37–3.52 (4H, m), 4.84
(1H, q, J=7.3Hz). 13-C-NMR (acetone-d6) δ: 4.85, 8.21, 46.28,
73.50. IR (neat) cm−1: 1313, 1127. MS (m/z): 214 (M+), 122, 94,
66.
Chart 5. Plausible Reaction Mechanism
act as a Lewis acid,10,11) the methanol coordinates with the
1,1-Bis(ethanesulfonyl)methane6) Colorless crystals; mp
metal peroxides to produce niobium(V) peroxide complexes. 101–103°C (lit.6) 100–101.5°C). 1H-NMR (acetone-d6) δ:
These peroxide complexes oxidize dithioacetals and revert 1.38 (6H, t, J=7.6Hz), 3.44 (4H, q, J=7.6Hz), 4.98 (2H, s).
back to the niobium(V) hydroxides (or a complex with the 13C-NMR (acetone-d6) δ: 5.31, 48.26, 66.63. IR (neat) cm−1:
solvent). The resulting niobium(V) hydroxides then react with 3452, 1635, 1316, 1129, 1050. MS (m/z): 200 (M+), 108, 80.
peroxide to reform the niobium(V) peroxide complexes.
Bis(benzenesulfonyl)methane6) Colorless crystals; mp
1
121–122°C (lit.6) 117–119°C). H-NMR (CDCl3) δ: 5.38 (2H,
s), 7.64 (4H, t, J=7.5Hz), 7.77 (2H, t, J=7.5Hz), 7.96 (4H, d,
Conclusion
The bissulfonylmethylene compounds (1) can be prepared t, J=7.5Hz). 13C-NMR (acetone-d6) δ: 73.11, 128.82, 129.23,
by the oxidation of thioacetals with 30% hydrogen peroxide in 134.50, 139.41. IR (neat) cm−1: 3616, 3235, 1642, 1328, 1152.
the presence of a catalytic amount of niobium(V) chloride in MS (m/z): 142 (M+−2×C6H5−H), 107, 91, 77.
methanol.
References
Experimental
All reagents were commercially obtained from Nacalai
Tesque, Inc., Wako Pure Chemical Industries, Ltd., Kanto
Chemical Co., Inc., Kishida Chemical, Co., Ltd., Tokyo
Chemical Industry, Co., Ltd. and Sigma-Aldrich Corp., and
used without further purification. Melting points were mea-
sured using a Yanaco micromelting point apparatus (MP-J3)
and are uncorrected. The 1H- and 13C-NMR spectra were
recorded by a JEOL (JNM-EX400) spectrometer as solutions
in CDCl3 using tetramethylsilane (TMS) or the residual CHCl3
peak as the internal standard. The IR spectra were recorded