Oxidative Cycloaddition of Thiophenes
J . Org. Chem., Vol. 62, No. 23, 1997 7935
1729 (CdO), 1464, 1440, 1189, 1165, 1104, 1060, 959 cm-1
;
75.87, 126.70, 127.15, 129.11, 134.93, 145.59; IR (KBr) 1642,
1441, 1373, 1352, 1277, 1263, 1081, 1059, 1038 cm-1; MS (70
eV) m/z (%) 256 (M+, 10.3), 208 (M+ - SO, 63.4), 191 (100),
176 (50.6), 159 (41.9). Anal. Calcd for C12H16O2S2: C, 56.22;
H, 6.29. Found: C, 56.09; H, 6.32.
MS (70 eV) m/z (%) 238 (M+, 4.4), 191 (75.3), 172 (53.5), 148
(100). Anal. Calcd for C13H18O2S: C, 65.51; H, 7.61. Found:
C, 65.41; H, 7.65.
1,8-Dim et h yl-11-t h ia t r icyclo[6.2.1.02,7]u n d ec-9-en -3-
on e 11-Oxid e (30c). Cycloa d d ition of 2,5-Dim eth ylth io-
p h en e w ith Cycloh ex-2-en on e (29b). 30c: (90 mg, 8%): mp
1,2,4,7-Tetr a m eth yl-3,10-d ith ia tr icyclo[5.2.1.02,6]d eca -
4,8-d ien e 3,10-Dioxid e (32c) (82 gm, 0.32 mmol, 18%): Rf
0.11 (ether/MeOH 20:1); mp 159 °C (from ether); 1H NMR
(CDCl3, 270 MHz) δ 1.52 (s, 3H, CH3), 1.69 (s, 3H, CH3), 1.73
1
80-82 °C (from ether/hexane); H NMR (270 MHz, CDCl3) δ
1.49 (s, 3H, CH3), 1.71 (s, 3H, CH3), 2.08-2.60 (m, 6H), 3.24
3
3
(d, 1H, J ) 3.9 Hz), 3.28 (d, 1H, J ) 3.9 Hz), 5.82 (d, 1H, J )
(s, 3H, CH3), 2.02 (s, 3H, CH3), 4.03 (s, 1H), 6.00 (d, 1H, J )
6.9 Hz), 6.20 (d, 1H, 3J ) 6.9 Hz); 13C NMR (67.9 MHz, CDCl3)
δ 13.68, 15.29, 21.71, 23.92, 38.87, 45.45, 55.42, 71.18, 71.43,
131.12, 135.42, 212.09; IR (KBr) 1700 (CdO), 1440, 1380, 1350,
1290, 1150, 1080, 900 cm-1; MS (70 eV) m/z (%) 224 (M+, 3)
and 176 (M+ - SO, 100). Anal. Calcd for C12H16O2S: C, 64.25;
H, 7.19. Found: C, 64.08; H, 6.87.
3
6.9 Hz), 6.02 (s, 1H), 6.12 (d, 1H, J ) 6.9 Hz); 13C NMR (67.9
MHz, CDCl3) δ 12.89, 12.98, 13.70, 14.20, 69.29, 71.12, 72.33,
81.82, 131.07, 133.78, 133.89, 145.48; IR (KBr) 1650, 1439,
1359, 1184, 1081, 1040, 906 cm-1; MS (70 eV) m/z (%) 256 (M+,
1.3), 208 (M+ - SO, 28.0), 191 (100), 176 (100), 159 (72.0). Anal.
Calcd for C12H16O2S2: C, 56.22; H, 6.29. Found: C, 56.12; H,
6.34.
1,8,9,10-Tetr a m eth yl-11-th ia tr icyclo[6.2.1.02,7]u n d ec-9-
en -3-on e 11-Oxid e (30d ). Cycloa d d it ion of 2,3,4,5-Di-
m eth ylth iop h en e w ith Cycloh ex-2-en on e (29b). 30d : (170
4,7-Dim eth ylin d a n on e (34): mp 71-72 °C (lit. 78 °C)32
(from hexane); 1H NMR (270 MHz, CDCl3) δ 2.31 (s, 3H, CH3),
1
3
3
mg, 25%): mp 132-133 °C (from ether); H NMR (270 MHz,
2.60 (s, 3H, CH3), 2.65 (t, 2H, J ) 5.6 Hz), 2.98 (t, 2H, J )
3
3
CDCl3) δ 1.48 (s, 3H, CH3), 1.66 (s, 3H, CH3), 1.68 (s, 3H, CH3),
1.79 (s, 3H, CH3), 1.89-2.41 (m, 6H), 3.17 (m, 1H), 3.18 (m,
1H); 13C NMR (67.9 MHz, CDCl3) δ 12.35, 12.42, 12.62, 14.02,
21.78, 23.67, 39.01, 46.51, 55.10, 71.81, 72.04, 130.93, 134.47,
212.70; IR (KBr) 1698 (CdO), 1445, 1376, 1057, 1027, 878
cm-1; MS (70 eV) m/z (%) 252 (M+, 12.9), 203 (42.6), 161 (82.3).
Anal. Calcd for C14H20O2S: C, 66.63; H, 7.99. Found: C,
66.75; H, 8.01.
5.6 Hz), 7.00 (d, 1H, J ) 7.7 Hz), 7.25 (d, 1H, J ) 7.7 Hz);
13C NMR (67.9 MHz, CDCl3) δ 17.39, 17.99, 24.28, 36.66,
126.20, 132.79, 134.19, 134.39, 135.95, 154.80, 208.46; IR (KBr)
1700 (CdO), 1580, 1490, 1440, 1380, 1320, 1240, 820 cm-1
;
MS (70 eV) m/z (%) 160 (M+, 100). HRMS m/z C11H14O2S Anal.
Calcd: 210.7150. Found: 210.7170.
5,8-Dim eth yltetr a lon e (35): mp 29-30 °C (lit. 31.5 °C)33
(from hexane); 1H NMR (270 MHz, CDCl3) δ 2.11 (m, 2H), 2.63
1,9,10,11-Tetr a m eth yl-12-th ia tr icyclo[7.2.1.02,8]d od ec-
10-en -3-on e 12-Oxid e (30e). Cycloa d d ition of 2,3,4,5-
Tetr a m eth ylth iop h en e w ith Cycloh ep t-2-en on e (29c).
3
3
3
(t, 2H, J ) 6.3 Hz), 2.84 (t, 2H, J ) 6.3 Hz), 6.98 (d, 1H, J
) 7.8 Hz), 7.20 (d, 1H, 3J ) 7.8 Hz). Anal. Calcd for
C12H14O: C, 82.72; H, 8.10. Found: C, 82.53; H, 8.11.
1
30e: (140 mg, 25%): mp 115-117 °C (from ether); H NMR
4,7-Dim eth yl-3,10-d ith ia tr icyclo[5.2.1.02,6]d eca -4,8-d i-
en e 3,10-Dioxid e (36). In an inert atmosphere and at -20
°C, BF3‚Et2O (1.5 mL, 12.2 mmol) was added to a solution of
2-methylthiophene (300 mg, 3.06 mmol) in dry CH2Cl2 (10 mL).
The reaction mixture was stirred for 10 min at -20 °C. Then
a solution of m-CPBA (680 mg, 3.95 mmol) in dry CH2Cl2 (15
mL) was added slowly. The reaction mixture was stirred at
-20 °C for another 3 h. Then the suspension was poured into
a mixture of concd aqueous NaHCO3 solution (20 mL) and CH2-
Cl2 (50 mL) and stirred for 20 min at ambient temperature.
The organic phase was separated, and the aqueous phase was
extracted with CH2Cl2 (3 × 20 mL). The combined organic
phase was washed with water and brine and dried over
anhydrous MgSO4. After removal of the solvent in vacuo, the
residue was chromatographed on silica gel to yield 36 (140 mg,
40%) as colorless crystals. 36: mp 148-149 °C (from benzene/
(270 MHz, CDCl3) δ 0.80-0.85 (m, 1H), 1.42 (s, 3H, CH3), 1.46
(s, 3H, CH3), 1.57 (m, 1H), 1.65 (s, 3H, CH3), 1.71 (m, 1H),
1.79 (m, 1H), 1.90 (s, 3H, CH3), 2.32 (m, 1H), 2.51 (m, 1H),
2.82 (ddd, 1H, J ) 1.5 Hz, 11.5 Hz, 11.5 Hz), 3.78 (d, 1H, J )
10.0 Hz); 13C NMR (67.9 MHz, CDCl3) δ 12.37, 12.47 (2C),
13.34, 23.52, 25.27, 27.14, 43.65, 45.61, 60.58, 70.41, 71.66,
129.58, 133.76, 210.80; IR (KBr) 2880, 1703 (CdO), 1456, 1134,
1095, 1056 cm-1; MS (70 eV) m/z (%) 266 (M+, 3), 218 (100),
190 (16). Anal. Calcd for C15H22O2S: C, 67.63; H, 8.32.
Found: C, 67.52; H, 8.28.
BF 3-Ca ta lyzed Oxid a tion of Dim eth ylth iop h en e (1a )
in th e Absen ce of Ad d ition a l Dien op h iles. BF3‚Et2O (2.0
mL, 16.1 mmol) was added to a solution of 2,5-dimethyl-
thiophene (400 mg, 3.57 mmol) in dry CH2Cl2 (10 mL) under
an inert atmosphere and at -20 °C. The reaction mixture was
stirred for 10 min at -20 °C. Then a solution of m-CPBA (900
mg, 5.20 mmol) in dry CH2Cl2 (20 mL) was added slowly. The
reaction mixture was stirred for another 2 h at -20 °C. Then
the suspension was poured into a mixture of a concd aqueous
solution of NaHCO3 (20 mL) and CH2Cl2 (50 mL). The
resulting mixture was stirred for 20 min at room temperature.
The organic phase was separated, and the aqueous phase was
extracted with CH2Cl2 (3 × 20 mL). The combined organic
phase was washed with water and brine and dried over
anhydrous MgSO4. After removal of the solvent in vacuo, the
residue was chromatographed on silica gel to give 32a -c.
1,2,4,7-Tetr a m eth yl-3,10-d ith ia tr icyclo[5.2.1.02,6]d eca -
4,8-d ien e 3,3,10-Tr ioxid e (32a ) (49 mg, 12%): Rf 0.40 (ether);
mp 176-178 °C (dec, from benzene); 1H NMR (270 MHz,
CDCl3) δ 1.57 (s, 3H, CH3), 1.74 (s, 3H, CH3), 1.87 (s, 3H, CH3),
2.00 (s, 3H, CH3), 3.65 (bs, 1H), 5.81 (d, 1H, 3J ) 6.9 Hz), 6.04
(bs, 1H), 6.25 (d, 1H, 3J ) 6.9 Hz); 13C NMR (67.9 MHz, CDCl3)
δ 9.60, 12.36, 13.46, 15.94, 61.24, 70.62, 71.93, 73.46, 127.58,
127.84, 136.15, 142.43; IR (KBr) 1440, 1284, 1146, 1079, 1058
cm-1; MS (70 eV) m/z (%) 224 (M+ - SO, 21.7), 160 (20.1), 145
(93.4). Anal. Calcd for C12H16O3S2: C, 52.92; H, 5.92.
Found: C, 52.86; H, 6.04.
1
hexane, dec); H NMR (270 MHz, CDCl3) δ 1.63 (s, 3H, CH3),
2.10 (dd, 3H, J ) 1.6 Hz, 2.0 Hz), 3.96 (m, 1H), 4.07 (dd, 1H,
J ) 4.1 Hz, 4.3 Hz), 4.82 (dd, 1H, J ) 4.1 Hz, 7.9 Hz), 5.80 (d,
1H, J ) 6.8 Hz), 5.82 (m, 1H), 6.37 (dd, 1H, J ) 4.1 Hz, 6.8
Hz); 13C NMR (67.9 MHz, CDCl3) δ 13.41, 13.73, 57.23, 62.71,
62.80, 75.02, 127.51, 127.69, 130.10, 147.46. IR (KBr) 1640,
1570, 1440, 1380, 1342, 1310, 1280, 1262, 1210, 1150, 1110,
1098, 1070, 1030 cm-1; MS (70 eV) m/z (%) 228 (M+, 1.5), 180
(M+ - SO, 22.8), 163 (100). Anal. Calcd for C15H20O2S2: C,
52.60; H, 5.30. Found: C, 52.76; H, 5.38.
2,3,4,5-Tetr a m eth ylth iop h en e S-Oxid e (31b). BF3‚Et2O
(1.5 mL, 12.2 mmol) was added to a solution of 2,3,4,5-
tetramethylthiophene (300 mg, 2.78 mmol) in dry CH2Cl2 (10
mL) under an inert atmosphere and at -20 °C. The reaction
mixture was stirred for 10 min at -20 °C. Then a solution of
m-CPBA (480 mg, 2.78 mmol) in dry CH2Cl2 (10 mL) was
added slowly. The reaction mixture was stirred for another 2
h at -20 °C. Then the suspension was poured into a mixture
of a concd aqueous solution of NaHCO3 (20 mL) and CH2Cl2
(50 mL). The resulting mixture was stirred for 20 min at room
temperature. The organic phase was separated, and the
aqueous phase was extracted with CH2Cl2 (3 × 20 mL). The
1,2,4,7-Tetr a m eth yl-3,10-d ith ia tr icyclo[5.2.1.02,6]d eca -
4,8-d ien e 3,10-Dioxid e (32b) (84 mg, 0.33 mmol, 18%): Rf
0.30 (ether/MeOH 20:1); mp 128-130 °C (from ether); 1H NMR
(270 MHz, CDCl3) δ 1.52 (s, 3H, CH3), 1.68 (s, 3H, CH3), 1.77
(s, 3H, CH3), 2.01 (s, 3H, CH3), 3.78 (bs, 1H), 5.63 (d, 1H, 3J )
6.6 Hz), 5.86 (bs, 1H), 6.27 (d, 1H, 3J ) 6.6 Hz); 13C NMR (67.9
MHz, CDCl3) δ 13.19, 13.50, 13.71, 18.94, 67.57, 72.27, 73.69,
(32) Mayer, F.; Mu¨ller, P. Chem. Ber. Dtsch. Ges. 1927, 60, 2278-
2283.
(33) (a) de Barry Barnett, E.; Sanders, F. G. J . Chem. Soc. 1933,
434-437. (b) Eisenbaum, E. J .; Hinman, C. W.; Springer, J . M.;
Burnham, J . W.; Chou, T. S.; Flanagan, P. W.; Hamming, M. C. J .
Org. Chem. 1971, 36, 2480-2485.