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Helvetica Chimica Acta Vol. 85 (2002)
J 7.6, CHCO2Et); 3.98 3.81( m, 1 OCH2Me); 1.37 (t, J 7.2, OCH2Me); 1.04 (t, J 7.2, 1OCH 2Me).
13C-NMR (75 MHz, CDCl3): 169.8 (CO); 168.1 (CO); 166.1 (CO); 148.1 (C); 147.8 (C); 128.3 (C); 119.7
(CH); 108.1 (CH); 106.2(CH); 101.3 (OCH2O); 79.9 (OCHAr); 62.7 (CH2O); 61.6 (CH2O); 49.8 (CH); 48.4
(CH); 13.9 (Me); 13.6 (Me). EI-MS: 350 (100, M ), 321 (0.83), 304 (13), 287 (2), 275 (9), 259 (10), 247 (4), 230
(19), 215 (4), 203 (27), 190 (12), 173 (17), 149 (85), 127 (79), 99 (69), 93 (6), 71 (4), 65 (10), 53 (8), 45 (4).
Anal. calc. for C17H18O8 (350.33): C 58.29, H 5.18; found: C 58.20, H 5.13.
Diethyl Tetrahydro-2-(4-methoxyphenyl)-5-oxofuran-3,4-dicarboxylate (5b). According to the G.P., with
dianion 2 (2.0 mmol) in THF (10 ml) and the THF (5 ml) soln. of anisaldehyde (384 mg, 2.8 mmol). The crude
product was purified by prep. TLC (SiO2, 20% AcOEt/hexane; double runs): 79 :4 :14 :3 mixture t,c/c,c/t,t/c,t-5b
(545 mg, 81%). Pale yellow solid. 1H-NMR (300 MHz, CDCl3): 7.37 7.24 (m, 2 arom. H of c,t, c,c, and t,t); 7.16
(d, J 8.7, 2 arom. H of t,c); 6.93, 6.87 (each app. d, J 8.7, 2 arom. H); 5.90 (c,t), 5.84 (t,c), 5.58 (c,c), 5.47 (t,t)
(each d, J 9.3, 7.8, 5.7, and 9.1, resp., OCHAr); 4.30 (q, J 7.2, OCH2Me of t,c); 4.35 4.10 (m, 2 OCH2Me of
c,t and t,t, OCH2Me of c,c); 4.20 (t,c), 4.06 (t,t), 3.99 (c,t) (each d, J 7.6, 10.8, and 9.3, resp., COCHCO); 4.15
(t,c), 3.53 (c,t) (each app. t, J 7.7 and 9.3, resp., CHCO2Et); 3.95 3.69 (m, OCH2Me of t,c, OCH2Me,
COCHCO and CHCO2Et of c,c, CHCO2Et of t,t, OMe of c,t, c,c, and t,t); 3.79 (s, OMe of t,c); 1.35 (t,c), 1.34 (c,t
and t,t), 1.29 (c,c) (each t, J 7.2, OCH2Me); 1.24 (c,t), 1.22 (t,t), 0.95 (t,c), 0.92 (c,c) (each t, J 7.2, 7.2, 7.2, and
7.6, resp., OCH2Me).
The pale yellow solid of diastereoisomer mixture 5b was recrystallized from AcOEt/hexane: pure t,c-5b.
White solid. M.p. 82 838. IR (nujol): 1801s, 1740s, 1693w, 1614m, 1581w, 1516m, 1454m, 1326s, 1304m, 1257m,
1241m, 1215m, 1181m, 1137m, 1015m, 968m, 847m, 806m. 1H-NMR (400 MHz, CDCl3): 7.18 (d, J 8.8, 1arom.
H); 6.90 (d, J 8.8, 1arom. H); 5.87 ( d, J 8.0, OCHAr); 4.33 (q, J 7.2, OCH2Me); 4.22 (d, J 7.2,
O2CCHCO2); 4.18 (app. t, J 7.8, CHCO2Et); 3.94 3.72 (m, OCH2Me); 3.82 (s, ArOMe); 1.37 (t, J 7.2,
OCH2Me); 0.98 (t, J 7.2, OCH2Me). 13C NMR (75 MHz, CDCl3): 170.0 (CO); 168.3 (CO); 166.3 (CO);
160.1 (C); 127.3 (CH, 2 peaks merged); 126.6 (C) ; 113.9 (CH, 2 peaks merged); 80.0 (OCHAr); 62.7 (OCH2);
61.5 (OCH2), 55.2 (OMe); 49.8 (CH); 48.5 (CH); 13.6 (Me). EI-MS: 336 (29, M ), 318 (2), 307 (1), 289 (8), 273
(1), 263 (9), 245 (5), 233 (2), 216 (10), 200 (40), 189 (17), 173 (22), 154 (32), 145 (18), 135 (81), 127 (100), 99
(93), 92 (7), 77 (22), 63 (6), 55 (13), 43 (6). Anal. calc. for C17H20O7 (336.35): C 60.71, H 5.99; found: C 60.38,
H 5.78.
Diethyl Tetrahydro-2-oxo-5-phenylfuran-3,4-dicarboxylate (5c). According to the G.P. with dianion 2
(2.0 mmol) in THF (10 ml) and a THF (2 ml) soln. of benzaldehyde (0.3 ml, 2.97 mmol). The crude product, a
71:6 :19 :4 mixture t,c/c,c/t,t/c,t-5c, was purified by radial chromatography (SiO2, 8% AcOEt/hexane):
68 :11:18 :3 mixture t,c/c,c/t,t/c,t-5c (478 mg, 78%). Pale yellow liquid. 1H-NMR (400 MHz, CDCl3): 7.48
7.24 (m, 5 arom. H); 5.97 (c,t), 5.91( t,c), 5.65 (c,c) and 5.56 (t,t) (each d, J 8.9, 7.0, 5.7, and 8.9, resp., OCHAr);
4.33 (q, J 7.1, OC H2Me of t,c); 4.31 4.12 ( m, COCHCO and CHCO2Et of t,c, 2 OCH2Me of c,t and t,t, and
OCH2Me of c,c); 4.09 (t,t), 4.02 (c,t), 3.95 (c,c) (each d, J 10.6, 9.3, and 7.2, resp., COCHCO); 3.92 3.67 (m,
OCH2Me of t,c, OCH2Me and CHCO2Et of c,c, CHCO2Et of t,t); 3.57 (t, CHCO2Et of c,t); 1.37 (t,c), 1.35 (c,t and
t,t), 1.32 (c,c) (each t, J 7.2, 7.2, and 7.2, resp., OCH2Me); 1.28 (c,t), 1.25 (t,t), 0.92 (t,c), and 0.87 (c,c) (each t,
J 7.0, 7.1, 7.2, and 7.2, resp., OCH2Me).
Attempted separation of the diastereoisomers was made by prep. TLC (SiO2, 20% AcOEt/hexane; double
runs) to give two bands of 5c (Fr. 1 and 2).
Fr. 1 (less polar) yielded c,t/t,t-5c (9 :91) contaminated with a small amount of t,c-5c. IR (neat): 3067m,
3038m, 2985m, 2940m, 2909m, 1789s, 1738s, 1498m, 1458m, 1372m, 1354m, 1305s, 1256s, 1213s, 1199s, 1157s,
1
1020s, 976m, 91 8m, 857m, 760m, 701s. H-NMR (300 MHz, CDCl3): 7.46 7.35 (m, 5 arom. H); 5.96 (c,t), 5.54
(t,t) (each d, J 9.0 and 8.8, resp., OCHAr); 4.34 4.15 (m, 2 OCH2Me); 4.07 (t,t), 4.00 (c,t) (each d, J 10.8
and 9.4, resp., COCHCO); 3.87 (dd, J 10.4, 8.9, CHCO2Et of t,t); 3.55 (app. t, J 9.1, CHCO2Et of c,t); 1.33
(app. t, J 7.2, OCH2Me); 1.24 (app. t, J 7.2, OCH2Me). 13C-NMR (75 MHz, CDCl3; major isomer t,t-5c):
169.2 (CO); 169.1 (CO); 166.2 (CO); 136.8 (C); 129.2 (CH); 128.7 (CH); 126.1 (CH); 80.8 (OCH); 62.6
(OCH2); 62.0 (OCH2); 51.9 (CH); 50.6 (CH); 13.92 (Me); 13.89 (Me).
Fr. 2 (more polar) yielded a 95 :5 mixture of the major t,c-5c contaminated with a small amount of c,c- and
t,t-5c. Pale yellow liquid. IR (neat): 3066w, 3036w, 2985m, 2940m, 2907m, 1791s, 1733s, 1607w, 1498m, 1457m,
1400m, 1382m, 1372m, 1314s, 1214s, 1159s, 1097m, 1020s, 964m, 855m, 752m, 700s. 1H-NMR (300 MHz, CDCl3):
7.41 7.20 ( m, 5 arom. H); 5.89 (d, J 7.6, OCHAr); 4.31( q, J 7.1, OC H2Me); 4.20 4.13 (m, COCHCO,
CHCO2Et); 3.89 3.64 (m, OCH2Me); 1.35 (t, J 7.2, OCH2Me); 0.90 (t, J 7.2, OCH2Me). 13C-NMR
(75 MHz, CDCl3; major isomer t,c-5c): 169.9 (CO); 168.1 (CO); 166.1 (CO); 134.6 (C); 129.0 (CH); 128.3
(CH, 2 peaks merged); 125.7 (CH, 2 peaks merged); 80.0 (OCHAr); 62.6 (OCH2); 61.4 (OCH2); 49.7 (CH);
48.9 (CH); 13.8 (Me); 13.2 (Me). EI-MS: 306 (15, M ), 278 (0.33), 260 (22), 243 (1), 232 (29), 215 (5), 203 (4),