1490 J . Org. Chem., Vol. 61, No. 4, 1996
Ben´ıtez et al.
3-[1-(ter t-Bu tyld im eth ylsilyloxy)vin -1-yl]fu r a n (5). A
suspension of anhyd zinc chloride (2.7 g, 20.0 mmol) in
triethylamine (5.3 mL , 40.0 mmol) was stirred at rt for 1 h
until it became milky. A solution of 3-acetylfuran (2.2 g, 20.0
mmol) in benzene (20 mL) was added followed by tert-
butyldimethylchlorosilane (6.0 g, 40.0 mmol). The reaction
was stirred at rt for 1 h then at 70 °C for 4 h. The reaction
was poured into ether (100 mL), filtered through Celite, and
concentrated. The residue was distilled to give 5 as a colorless
oil (2.12 g, 54%): bp 48-50 °C (0.5 mmHg); IR (CHCl3) 2958,
2932, 1633, 1561, 1508, 1323, 1168, 1015, 833 cm-1; 1H NMR
(CDCl3, 200 MHz) δ 7.52 (s, 1H), 7.34 (t, J ) 1.8 Hz, 1H), 6.46
(dd, J ) 1.8, 0.8 Hz, 1H), 4.57 (d, J ) 1.5 Hz, 1H), 4.29 (d, J
) 1.5 Hz, 1H), 0.98 (s, 9H), 0.21 (s, 6H); 13C NMR (CDCl3, 25
MHz) δ 150.76, 143.60, 140.64, 125.97, 108.54, 90.92, 26.22,
18.67, -4.19; MS (EI) m/ z (rel intensity) 224 (M+, 18), 183
(100). Anal. Calcd for C12H20O2Si: C, 64.24; H, 8.98. Found:
C, 64.13; H, 9.16.
(5aRS,8aRS)-7-P h en yl-5,5a,8a,8b-tetr ah ydr o-3aH-1-oxa-
7-a za -a s-in d a cen e-4,6,8-tr ion e (12), N,N-d ip h en yl (1SR,
2SR,8SR,9SR,10RS)-6-(ter t-b u t yld im et h ylsilyloxy)-11-
oxa tr icyclo[6.2.1.02,7]u n d ec-6-en e-3,4,9,10-tetr a ca r boxim -
id e (13), a n d N,N-Dip h en yl (1SR,2SR,8SR,9RS,10SR)-6-
(ter t -b u t yld im et h ylsilyloxy)-11-oxa t r icyclo[6.2.1.02,7]-
u n d ec-6-en e-3,4,9,10-tetr a ca r boxim id e (14). A solution of
the vinylfuran 5 (0.3 g, 1.3 mmol) and N-phenylmaleimide (0.7
g, 4.0 mmol) in toluene (8 mL) was stirred at rt for 48 h.
Compound 13 precipitated from the reaction (220 mg) mixture
and was collected by filtration. The filtrate was evaporated
in vacuo, and the residue was purified by flash chromatogra-
phy (hexane-acetone, 9:1) to yield compound 12 (33 mg, 9%),
compound 13 (53 mg; total 273 mg, 36%), and compound 14
(146 mg, 19%) as solids. Spectroscopic data for 12: mp 173-
175 °C (hexane-EtOAc); IR (CHCl3) 3021, 1723, 1693, 1500,
1
1380 cm-1; H NMR (CDCl3, 200 MHz) δ 7.54 (d, J ) 2.5 Hz,
1H), 7.52-7.34 (m, 3H), 7.28-7.18 (m, 2H), 6.76 (d, J ) 2.1
Hz, 1H), 4.52 (d, J ) 8.1 Hz, 1H), 3.84 (dt, J ) 8.4, 2.9 Hz,
1H), 3.35 (dd, J ) 17.8, 2.9 Hz, 1H), 2.87 (dd, J ) 17.8, 8.4
Hz, 1H); 13C NMR (CDCl3, 25 MHz) δ 189.41, 175.89, 171.43,
156.69, 146.28, 131.63, 129.74, 129.50, 126.61, 122.98, 107.40,
40.70, 39.19, 34.99; MS (EI) m/ z (rel intensity) 281(M+, 40),
134 (100). Anal. Calcd for C16H11NO4‚1/10H2O: C, 67.89; H,
3.99; N, 4.95. Found: C, 67.82; H, 4.06; N, 4.84. Spectroscopic
data for 13: mp 260-262 °C (CH2Cl2-hexane); IR (CHCl3)
3025, 2932, 1780, 1719, 1501, 1387, 1192, 829 cm-1; 1H NMR
(CDCl3, 200 MHz) δ 7.52-7.33 (m, 6H), 7.37-7.16 (m, 4H),
5.65 (s, 1H), 5.35 (s, 1H), 3.43 (t, J ) 8.4 Hz, 1H), 3.31 (ddd,
J ) 8.7, 5.8, 1.9 Hz, 1H), 3.21 (d, J ) 7.1 Hz, 1H), 3.14 (d, J
) 7.1 Hz, 1H), 2.79 (dd, J ) 15.4, 1.8 Hz , 1H), 2.50 (d, J ) 8.4
Hz, 1H), 2.35 (dd, J ) 15.4, 5.6 Hz, 1H), 0.94 (s, 9H), 0.20 (s,
3H), 0.14 (s, 3H); 13C NMR (CDCl3, 25 MHz) δ 177.71, 176.30,
176.18, 175.55, 142.94, 132.27, 129.63, 129.27, 129.12, 126.97,
126.88, 115.62, 80.77, 78.02, 49.97, 44.83, 41.25, 40.86, 30.20,
25.98, 18.56, -3.35,-3.61; MS (CI) m/ z (rel intensity) 588 (M+
+ 18, 100). Anal. Calcd for C32H34N2O6Si: C, 67.43; H, 6.00;
N, 4.91. Found: C, 67.28; H, 5.97; N, 4.89. Spectroscopic data
for 14: mp 204-205 °C (CH2Cl2-hexane); IR (CHCl3) 3020,
2932, 1778, 1718, 1500, 1386, 1367, 1186, 829 cm-1; 1H NMR
(CDCl3, 200 MHz) δ 7.56-7.31 (m, 6H), 7.27-7.09 (m, 4H),
5.59 (d, J ) 6.1 Hz, 1H), 5.36 (d, J ) 5.4 Hz, 1H), 3.74 (dd, J
) 9.3, 6.1 Hz, 1H), 3.65 (dd, J ) 9.2, 5.7 Hz, 1H), 3.29 (m,
2H), 2.86 (d, J ) 15.1 Hz, 1H), 2.51 (m, 1H), 2.31 (dd, J )
15.4, 3.7 Hz, 1H), 0.94 (s, 9H), 0.20 (s, 3H), 0.13 (s, 3H); 13C
NMR (CDCl3, 25 MHz) δ 177.51, 176.37, 175.07, 173.25,
144.82, 132.36, 132.05, 129.80, 129.61, 129.42, 129.08, 126.78,
113.20, 79.57, 77.10, 51.57, 50.84, 42.45, 41.23, 41.02, 29.98,
26.00, 18.47, -3.37, -3.44; MS (EI) m/ z (rel intensity) 588
(M+ - 57, 100). Anal. Calcd for C32H34N2O6Si‚1/4 H2O: C,
66.82; H, 6.04; N, 4.87. Found: C, 66.68; H, 6.00; N, 4.92.
(1SR,2SR,8SR,9SR,10RS)-6-(ter t-Bu tyldim eth ylsilyloxy)-
11-oxa tr icyclo[6.2.1.02,7]u n d ec-6-en e-3,4,9,10-tetr a ca r box-
ylic Acid Tetr a m eth yl Ester (17) a n d (1SR,2SR,8SR,9RS,
10S R )-6-(t er t -b u t yld im e t h ylsilyloxy)-11-oxa t r icyclo-
[6.2.1.02,7]u n d ec-6-en e-3,4,9,10-tetr a ca r boxylic Acid Tet-
r a m eth yl Ester (18). A solution of the vinylfuran 5 (500 mg,
2.2 mmol) and dimethyl maleate (0.96 mL, 6.6 mmol) in
toluene (10 mL) was heated at reflux for 56 h. The solvent
was removed, and the crude product was purified by flash
chromatography (hexane-acetone, 4:1) to obtain the double
addition adducts 17 and 18 (0.44 g, 39%). A pure sample of
each was obtained by flash chromatography (hexane-EtOAc,
7:3). Spectroscopic data for 17: IR (CHCl3) 3026, 2955, 1739,
1438, 1364, 1259, 1169, 841 cm-1; 1H NMR (CDCl3, 200 MHz)
δ 5.30 (s, 1H), 4.88 (s, 1H), 3.74 (s, 3H), 3.69 (s, 3H), 3.68 (s,
3H), 3.67 (s, 3H), 3.40 (ddd, J ) 7.8, 3.5, 1.4 Hz, 1H), 3.25 (d,
J ) 9.5 Hz, 1H), 3.14 (d, J ) 9.2 Hz, 1H), 2.61 (dt, J ) 18.0,
1.7 Hz, 1H), 2.45-2.25 (m, 3H), 0.94 (s, 9H), 0.14(s, 3H), 0.12
(s, 3H); 13C NMR (CDCl3, 25 MHz) δ 173.62, 173.46, 171.28,
141.58, 117.80, 81.56, 78.54, 53.51, 52.63, 49.98, 43.69, 42.40,
41.74, 31.50, 26.02, 18.50, -3.88; MS (EI) m/ z (rel intensity)
512 (M+, 6), 455 (68), 367 (100). Anal. Calcd for C24H36O10Si:
C, 56.23; H, 7.08. Found: C, 56.48; H, 7.10. Spectroscopic
data for 18: IR (CHCl3) 3027, 2954, 1739, 1438, 1361, 1258,
1175, 841 cm-1; 1H NMR (CDCl3, 200 MHz) δ 5.22 (d, J ) 5.6
4-(ter t-Bu t yld im et h ylsilyloxy)b en zofu r a n -6,7-d ica r -
boxylic Acid Dim eth yl Ester (6) a n d (1SR,2RS,8RS)-6-
(ter t -b u t yld im et h ylsilyloxy)-11-oxa t r icyclo[6.2.1.02,7]-
u n d eca -3,6,9-tr ien e-3,4,9,10-tetr a ca r boxylic Acid Tetr a -
m eth yl Ester (7). A solution of vinylfuran 5 (250 mg, 1.1
mmol) and dimethyl acetylenedicarboxylate (0.41 mL, 3.3
mmol) in toluene (4 mL) was stirred at rt for 72 h. The solvent
was removed and the residue purified by flash chromatography
(hexane-EtOAc, 9:1) to obtain the benzofuran 6 (156 mg, 39%)
and compound 7 (90 mg, 16%) as oils. Spectroscopic data for
6: IR (CHCl3) 3024, 2958, 1729, 1438, 1272, 1044 cm-1 1H
;
NMR (CDCl3, 200 MHz) δ 7.67 (d, J ) 2.2 Hz, 1H), 7.12 (s,
1H), 6.82 (d, J ) 2.2 Hz, 1H), 3.99 (s, 3 H), 3.91 (s, 3H), 1.02
(s, 9H), 0.25 (s, 6H); 13C NMR (CDCl3, 25 MHz) δ 167.63,
166.79, 153.69, 151.12, 147.19, 127.69, 124.97, 113.83, 112.85,
104.99, 53.52, 53.23, 26.06, 18.73, -3.88; MS (EI) m/ z (rel
intensity) 364 (M+, 60), 307 (100). Anal. Calcd for C18H24O6-
Si: C, 59.32; H, 6.64. Found: C, 59.22 ; H, 6.77. Spectroscopic
data for 7: IR (CHCl3) 3026, 2955, 1722, 1639, 1437, 1265,
1
842 cm-1; H NMR (CDCl3, 200 MHz) δ 5.59 (d, J ) 1.2 Hz,
1H), 5.08 (d, J ) 1.2 Hz, 1H), 3.70 (s, 3 H), 3.67 (s, 3H), 3.64
(s, 3H), 3.61 (s, 3H), 2.93 (br s, 3H), 0.81 (s, 9H), 0.01 (s, 3H),
0.004 (s, 3H); 13C NMR (CDCl3, 25 MHz) δ 167.44, 166.34,
162.67, 162.24, 145.54, 143.98, 142.00, 138.18, 135.14, 109.91,
82.12, 80.07, 52.50, 52.37, 44.31, 34.80, 25.54, 18.06, -4.09,
-4.46; MS (EI) m/ z (rel intensity) 324 (M+ - 184, 19), 153
(100). Anal. Calcd for C24H32O10Si: C, 56.67; H, 6.34.
Found: C, 56.63; H, 6.42.
Dim eth yl F u r a n -3,4-d ica r boxyla te a n d 4-(ter t-bu tyld i-
m eth ylsilyloxy)p h th a lic Acid Dim eth yl Ester (8).
A
solution of 7 (0.5 g, 0.98 mmol) and p-toluenesulfonic acid (18
mg, 0.098 mmol) in CH2Cl2 (12 mL) was stirred at rt for 2 h.
The solvent was removed and the residue purified by prep TLC
(hexane-acetone, 7:3) to give dimethyl furan-3,4-dicarboxylate
(76 mg, 42%) which was identical to a commercial sample and
compound 8 (140 mg, 49%) as an oil: IR (CHCl3) 3028, 2955,
1723, 1603, 1305, 1125, 845 cm-1; 1H NMR (CDCl3, 200 MHz)
δ 7.74 (d, J ) 8.5 Hz, 1H), 7.21 (d, J ) 2.4 Hz, 1H), 6.93 (dd,
J ) 8.5, 2.5 Hz, 1H), 3.91 (s, 3H), 3.87 (s, 3H), 0.98 (s, 9H),
0.23 (s, 6H); 13C NMR (CDCl3, 25 MHz) δ 168.59, 166.96,
158.70, 135.47, 131.43, 123.01, 121.59, 119.89, 52.67, 52.33,
25.51, 18.16, -4.44; MS (EI) m/ z (rel intensity) 324 (M+, 6),
235 (100). Anal. Calcd for C16H24O5Si: C, 59.23; H, 7.45.
Found: C, 59.57; H, 7.75.
4-Hyd r oxyn a p h th o[1,2-b]fu r a n -6,9-d ion e (11). A solu-
tion of vinylfuran 5 (0.5 g, 2.2 mmol) and 1,4-benzoquinone
(0.71 g, 6.6 mmol) in toluene (10 mL) was stirred at rt for 5
days. The solvent was removed, and the dark residue was
purified by prep TLC (hexane-acetone, 7:3) to give compound
11 (278 mg, 45%) as a red solid, mp 220 °C dec. (toluene); IR
(CHCl3) 3115, 1658, 1572, 1361, 1336, 1277, 1079 cm-1 1H
;
NMR (CDCl3-DMSO-d6, 200 MHz) δ 10.80 (br s, 1H, D2O
exchange), 7.82 (d, J ) 2.2 Hz, 1H), 7.39 (s, 1H), 7.05 (d, J )
2.1 Hz, 1H), 6.85 (s, 2H); 13C NMR (CDCl3-DMSO-d6, 25 MHz)
δ 187.97, 182.71, 156.71, 153.67, 147.53, 138.94, 137.11,
130.65, 122.65, 110.51, 106.42, 104.32; MS (EI) m/ z (rel
intensity) 214 (M+, 100), 186 (26), 158 (18). Anal. Calcd for
C12H6O4‚1/7H2O: C, 66.49; H, 2.92. Found: C, 66.19; H, 2.93.