C. Bongards, W. Gärtner
FULL PAPER
(0.95 mL, 5.4 mmol) was heated under argon to 75–80 °C for
45 min and subsequently refluxed at 160–170 °C for 5.5 h. Purifica-
tion of the resulting solution by fractionating distillation in vacuo,
followed by column chromatography with n-hexane, ethyl acetate,
and 2-propanol (49:49:2) as eluent yielded the product 23 (0.68 g,
2.8 mmol, 51%) as a yellow, clear liquid, b.p. 86 °C (0.032–
0.035 mbar). 1H NMR (400 MHz, CDCl3): δ = 1.22 [t, 3J =
(1.4 mL), to which a small amount of molecular sieves (3 Å) was
added, was refluxed for 19 h in the dark and under argon. The
reaction mixture was decanted from the molecular sieves which was
repeatedly washed with chloroform as long as the solvent showed
colour. The combined organic phases were washed with a solution
of Na2CO3 (2 , 3ϫ100 mL), with a solution of saturated KH2PO4
(3ϫ100 mL), and with
a solution of saturated NaHCO3
7.03 Hz, 3 H, PO(OCH2CH3)2], 1.27 [t, 3J
= 7.07 Hz, 3 H, (3ϫ100 mL). After drying over Na2SO4, the solvent was evapo-
PO(OCH2CH3)2], 1.68 (dq, Jd = 4.91, Jq = 0.93 Hz, 3 H, 31-CH3), rated. Column chromatography of the remaining raw material
2.16 (d, J = 3.33 Hz, 3 H, 21CH3), 2.50–2.65 (m, 2 H, 5-CH2), 3.03– (0.49 g) with dichloromethane and ethyl acetate (49:1) as eluent
3.06 (m, 0.5 H, 1-CH), 3.09–3.12 (m, 0.5 H, 1-CH), 3.97–4.13 [m,
yielded the expected reaction product 26 (0.30 g, 0.8 mmol, 76%)
1
1
4 H, PO(OCH2CH3)2] ppm. 13C NMR (101 MHz, DEPT 135, H/ as yellow crystals, m.p. 151–152 °C. H NMR (400 MHz, CDCl3):
1
13C-COSY, CDCl3): δ = 8.29 (d, JC,H = 1.92 Hz, C-31), 16.40 [d,
δ = 1.57 [s, 9 H, CO2C(CH3)3], 1.93 (s, 3 H, 91-CH3), 2.09 (s, 3 H,
81-CH3), 2.09 (s, 3 H, 41-CH3), 2.52 (t, 3J = 8.00 Hz, 2 H, 32-CH2),
2
3JC,P = 5.49 Hz, PO(OCH2CH3)2], 16.84 (C-21), 36.44 (d, JC,P
=
=
1
2
3
3.83 Hz, C-5), 41.72 (d, JC,P = 144.99 Hz, C-1), 62.12 [d, JC,P
2.99 (t, J = 7.80 Hz, 2 H, 31-CH2), 3.65 (s, 3 H, CO2CH3), 5.88 (s,
6.89 Hz, PO(OCH2CH3)2], 62.60 [d, 2JC,P
=
6.98 Hz,
1 H, 6-CH), 9.69 (br. s, 1 H, NH) ppm. 13C NMR (101 MHz,
PO(OCH2CH3)2], 138.84 (d, 1JC,H = 9.94 Hz, C-3), 164.53 (d, 1JC,H
CDCl3): δ =
8.91 (C-91), 9.87 (C-41), 20.52 (C-81), 28.37
= 8.79 Hz, C-2), 206.37 (d, JC,H = 2.82 Hz, C-4) ppm. IR (KBr): [CO2C(CH3)3], 29.69 (C-31), 34.90 (C-32), 51.48 (CO2CH3), 81.47
1
ν = 2985, 2931, 1702, 1644, 1445, 1388, 1329, 1258, 1236, 1210, [CO2C(CH3)3], 95.81 (C-6), 122.89, 123.08, 126.40, 128.36 (C-2,-4,
˜
1164, 1027, 967, 888, 797, 731, 693, 655, 600, 532, 491 cm–1. MS
-5,-9), 123.17 (C-3), 146.86 (C-7), 147.11 (C-8), 160.11 [CO2C-
(EI, 50 °C): m/z (%) = 246 (74) [M+], 231 (1), 218 (22), 203 (1), 190 (CH ) ], 169.03 (C-10), 173.60 (CO CH ) ppm. IR (KBr): ν = 3447,
˜
3 3
2
3
(72), 173 (14), 162 (5), 136 (12), 108 (100), 92 (15), 81 (37), 65 (9), 3067, 3007, 2974, 2953, 2930, 1758, 1736, 1682, 1653, 1625, 1449,
53 (16), 41 (15), 29 (13). HRMS (ESI pos, methanol + dichloro- 1367, 1272, 1252, 1192, 1171, 1137, 1096, 1007, 946, 845, 809, 753,
methane): m/z: calcd. for C11H19NaO4P [M + Na]+: 269.091319; 712, 678, 603, 571 cm–1. UV/Vis (n-hexane): λmax (ε) = 254 (30400),
found: 269.091189.
387 (44400), 407 nm (41100). MS (EI, 130 °C): m/z (%) = 389 (19)
[M+], 333 (100), 302 (9), 289 (11), 288 (11), 273 (24), 272 (2), 260
(11), 258 (2), 256 (4), 255 (4), 242 (7), 230 (9), 227 (5), 216 (7), 214
(3), 186 (4), 144 (2), 128 (4), 57 (2). HRMS (EI): m/z: calcd. for
C21H27NO6: 389.183839; found: 389.183447.
tert-Butyl 5-{[4-Ethyl-3-methyl-5-oxofuran-2(5H)-ylidene]methyl}-3-
[2-(methoxycarbonyl)ethyl]-4-methyl-1H-pyrrole-2-carboxylate (25):
A solution of the pyrrole 24 (0.31 g, 1.1 mmol), the furanone 10
(0.13 g, 1.0 mmol), and DBU (0.36 mL, 2.4 mmol) in absolute THF
(1.4 mL), to which a small amount of molecular sieves (3 Å) was
added, was refluxed for 19 h in the dark and under argon. The
reaction mixture was decanted from the molecular sieves which was
repeatedly washed with chloroform as long as the solvent showed
colour. The combined organic phases were washed with a solution
of Na2CO3 (2 , 3ϫ100 mL), with a solution of saturated KH2PO4
tert-Butyl 5-{[4-Ethyl-3-methyl-5-oxothiophen-2(5H)-ylidene]meth-
yl}-3-[2-(methoxycarbonyl)ethyl]-4-methyl-1H-pyrrole-2-carboxylate
(27): A solution of the pyrrole 24 (0.30 g, 1.0 mmol), the thio-
phenone 14 (0.15 g, 1.1 mmol), and DBU (0.35 mL, 2.3 mmol) in
absolute THF (1.4 mL), to which a small amount of molecular
sieves (3 Å) was added, was refluxed for 19 h in the dark and under
argon. The reaction mixture was decanted from the molecular si-
eves which was repeatedly washed with chloroform, as long as the
solvent showed colour. The combined organic phases were washed
with a solution of Na2CO3 (2 , 3ϫ100 mL), with a solution of
saturated KH2PO4 (3ϫ100 mL), and with a solution of saturated
NaHCO3 (3ϫ100 mL). After drying over Na2SO4, the solvent was
evaporated. Column chromatography of the remaining crude mate-
rial (0.58 g) with dichloromethane and ethyl acetate (19:1) as eluent
yielded the expected reaction product 27 (0.21 g, 0.5 mmol, 49%)
as a yellow-orange solid, m.p. 67–68 °C. 1H NMR (400 MHz,
CDCl3): δ = 1.06 (t, 3J = 7.58 Hz, 3 H, 92-CH3), 1.56 [s, 9 H,
CO2C(CH3)3], 2.12 (s, 3 H, 81-CH3), 2.27 (s, 3 H, 41-CH3), 2.42 (q,
3J = 7.60 Hz, 2 H, 91-CH2), 2.52 (t, 3J = 7.87 Hz, 2 H, 32-CH2),
(3ϫ100 mL), and with
a solution of saturated NaHCO3
(3ϫ100 mL). After drying over Na2SO4, the solvent was evapo-
rated. Column chromatography of the remaining crude material
(0.46 g) with dichloromethane and ethyl acetate (49:1) as eluent
yielded the expected reaction product 25 (0.36 g, 0.9 mmol, 86%)
1
as yellow crystals, m.p. 134–135 °C. H NMR (400 MHz, CDCl3):
δ = 1.12 (t, 3J = 7.61 Hz, 3 H, 92-CH3), 1.57 [s, 9 H, CO2C-
(CH3)3], 2.09 (s, 3 H, 41-CH3), 2.11 (s, 3 H, 81-CH3), 2.37 (q, J =
3
7.66 Hz, 2 H, 91-CH2), 2.52 (t, J = 7.87 Hz, 2 H, 32-CH2), 2.99 (t,
3
3J = 8.00 Hz, 2 H, 31-CH2), 3.65 (s, 3 H, CO2CH3), 5.88 (s, 1 H, 6-
CH), 9.70 (br. s, 1 H, NH) ppm. 13C NMR (101 MHz, CDCl3): δ
= 9.64 (C-41), 12.77 (C-92), 17.28 (C-91), 20.51 (C-81), 28.36
[C(CH3)3], 31.20 (C-31), 34.85 (C-32), 51.47 (CO2CH3), 81.35
[C(CH3)3], 95.90 (C-6), 123.15 (C-3), 125.55, 126.45, 128.37, 128.40
(C-2,-4,-5,-9), 146.59, 146.80 (C-7,-8), 160.07 [CO2C(CH3)3],
3
2.99 (t, J = 7.89 Hz, 2 H, 31-CH2), 3.64 (s, 3 H, CO2CH3), 6.93 (s,
1 H, 6-CH), 8.98 (br. s, 1 H, NH) ppm. 13C NMR (101 MHz,
CDCl3): δ = 9.07 (C-41), 12.66 (C-91), 13.11 (C-92), 18.97 (C-81),
20.35 (C-31), 28.33 [CO2C(CH3)3], 34.64 (C-32), 51.48 (CO2CH3),
81.69 [CO2C(CH3)3], 114.31 (C-6), 124.28, 125.66, 127.87, 129.07,
131.21 (C-2,-3,-4,-5,-7), 139.59 (C-9), 153.09 (C-8), 159.82
168.96 (C-10), 173.61 (CO CH ) ppm. IR (KBr): ν = 3448, 3066,
˜
2
3
2978, 2878, 1759, 1735, 1680, 1622, 1445, 1394, 1367, 1298, 1278,
1268, 1256, 1193, 1172, 1161, 1138, 1131, 1115, 1097, 1006, 944,
848, 673, 613 cm–1. UV/Vis (n-hexane): λmax (ε) = 254 (32000), 389
(48100), 409 nm (45200). MS (EI, 130 °C): m/z (%) = 403 (18) [M+],
347 (100), 316 (7), 303 (10), 287 (20), 286 (2), 274 (9), 272 (3), 270
(3), 269 (2), 256 (5), 254 (2), 244 (7), 241 (3), 230 (5), 228 (3),
226 (2), 200 (3), 135 (3). HRMS (EI): m/z: calcd. for C22H29NO6:
403.199489; found: 403.199617.
[CO C(CH ) ], 173.44 (CO CH ), 192.32 (C-10) ppm. IR (KBr): ν
˜
2
3 3
2
3
= 3429, 2974, 2952, 2934, 2875, 1740, 1675, 1608, 1583, 1537, 1437,
1383, 1368, 1276, 1197, 1165, 1140, 1054, 985, 961, 884, 847, 816,
778, 741, 708, 649, 545, 514, 473 cm–1. UV/Vis (n-hexane): λmax (ε)
= 267 (12900), 401 (21800), 419 nm (21300). MS (EI, 120 °C): m/z
(%) = 419 (26) [M+], 363 (100), 317 (13), 303 (24), 290 (6), 244 (3),
tert-Butyl 5-{[3,4-Dimethyl-5-oxofuran-2(5H)-ylidene]methyl}-3-[2-
(methoxycarbonyl)ethyl]-4-methyl-1H-pyrrole-2-carboxylate (26): A 216 (2), 166 (1), 129 (2), 91 (1), 73 (1), 57 (3). HRMS (ESI pos,
solution of the pyrrole 24 (0.30 g, 1.0 mmol), the furanone 11
(0.11 g, 1.0 mmol), and DBU (0.35 mL, 2.3 mmol) in absolute THF
methanol + dichloromethane): m/z: calcd. for C22H29NNaO5S [M
+ Na]+: 442.166415; found: 442.16614.
5756
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Eur. J. Org. Chem. 2007, 5749–5758