A. Marrocchi et al. / Tetrahedron 57 02001) 4959±4965
4963
4.1.4. 11c-Nitro-2,3,4a,5,11b,11c-hexahydronaphtho[2,1-
b]benzo[b]furan-451H)-one 56a). It was obtained 535%
yield) by column chromatography 5SiO2, 4:1 hexane/ethyl
acetate) from the crude reaction mixture of the cyclo-
addition between 1a and 2 performed under high pressure
5entry 1ÐTable 1);white microcrystalline solid, mp
1258C 5dec.) 52:1 hexane/ethyl acetate);5found: C, 67.6;
H, 5.3;N, 4.8. C 16H15NO4 requires C, 67.36;H, 5.30;N,
4.91%);IR 1722 5s, C vO), 1546 5s, ±NO2) cm21; 1H NMR
d 2.06 5m, 1H, H-2), 2.32 5ddd, 1H, J18.0, 7.8, 3.4 Hz,
H-5), 2.38 5m, 1H, H-2), 2.56 5ddd, 1H, J14.3, 7.8, 1.2 Hz,
H-3), 2.70 5m, 1H, H-3), 2.73 5m, 1H, H-1), 3.05 5m, 1H,
H-1), 3.09 5ddd, 1H, J18.0, 3.2, 1.0 Hz, H-5), 3.65 5dt, 1H,
J7.8, 1.0 Hz, H-4a), 4.08 5dt, 1H, J3.0, 1.0 Hz, H-11b),
5.11 5ddd, 1H, J3.4, 3.2, 3.0 Hz, H-6), 6.94 5ddd, 1H,
J7.6, 7.5, 0.9 Hz, H-10), 7.23 5m, 1H, H-11), 7.26 5m,
1H, H-9); 13C NMR d 19.2 5C-5), 21.3 5C-2), 33.8 5C-1),
40.0 5C-3), 42.3 5C-11b), 52.8 5C-4a), 93.1 5C-11c), 94.3
5C-6), 110.3 5C-8), 122.1 5C-10), 123.5 5C-11a), 123.8
5C-11), 129.0 5C-9), 150.7 5C-7a), 157.6 5C-6a), 205.1
5C-4).
MS m/e 5rel. int.) 76 527), 104 513), 152 534), 180 582),
208 599), 236 5M1, 100).
4.1.7. 2,3,5,6-Tetrahydronaphtho[2,1-b]benzo[b]thiophen-
451H)-one 57b). The reaction mixture obtained by the
cycloaddition reaction between 1b and 2 performed under
high pressure 5entry 3ÐTable 1) was treated with DBN as
described above for the synthesis of 7a. Usual work up and
chromatography on silica gel 5eluent: 4:1 hexane/ethyl
acetate) afforded pure 7b 537% overall yield) as white crys-
talline solid, mp 162±1638C 5methanol);5found: C, 75.7;H,
5.6. C16H14OS requires C, 75.55;H, 5.55%);IR 1642 5s,
1
CvO) cm21; H NMR d 2.17 5m, 2H, Hs-2), 2.56 5dd,
2H, J7.0, 6.3 Hz, Hs-3), 2.70 5dd, 2H, J9.2, 8.2 Hz,
Hs-5), 2.92 5dd, 2H, J9.2, 8.2 Hz, Hs-6), 3.12 5dd, 2H,
J6.3, 6.2 Hz, Hs-1), 7.31 5ddd, 1H, J7.9, 7.2, 1.2 Hz,
H-9), 7.38 5ddd, 1H, J7.8, 7.2, 1.2 Hz, H-10), 7.82 5dd,
1H, J7.9, 1.2 Hz, H-8), 7.98 5dd, 1H, J7.8, 1.2 Hz,
H-11); 13C NMR d 20.8 5C-5), 21.9 5C-6), 22.4 5C-2),
27.5 5C-1), 37.5 5C-3), 111.8 5C-8), 114.4 5C-11a), 119.9
5C-11), 123.6 5C-10), 123.9 5C-9), 125.3 5C-11b), 125.8
5C-4a), 149.1 5C-11c), 155.5 5C-7a), 160.6 5C-6a), 197.5
5C-4);MS m/e 5rel. int.) 99 512), 152 515), 165 519), 184
522), 197 574), 211 533), 226 578), 254 5M1, 100).
4.1.5. 2,3,5,6-Tetrahydronaphtho[2,1-b]benzo[b]furan-
451H)-one 57a). The crude reaction mixture obtained by
cycloaddition reaction of 1a and 2 5entry 1ÐTable 1)
dissolved in dry THF 56 mL) was treated with DBN
50.28 mL) for 0.5 h at 08C, then poured into H2O and
extracted with ether. The organic layer was washed with
brine, dried 5Na2SO4) and evaporated in vacuo. Chroma-
tography on silica gel of the crude product and elution
with 4:1 hexane/ethyl acetate gave pure 7a 543% overall
yield) as a white microcrystalline solid, mp 142±1438C
52:1 hexane/ethyl acetate);5found: C, 80.5;H, 6.0.
C16H14O2 requires C, 80.65;H, 5.92%);IR 1642 5s,
4.1.8. 2,3-Dihydronaphtho[2,1-b]benzo[b]thiophen-451H)-
one 58b). The 1b±2 reaction mixture obtained, according to
entry 3ÐTable 1, was treated with DBN as described
above for the synthesis of 8a. Usual work up and column
chromatography of the residue 54:1 hexane/ethyl acetate)
gave pure 8b 537% overall yield) as a pale yellow solid,
mp 140±1418C 5ethanol);5found: C, 76.3;H, 4.8.
C16H12OS requires C, 76.16;H, 4.79%);IR 1675 5s,
1
CvO) cm21; H NMR d 2.34 5m, 2H, Hs-2), 2.77 5dd,
1
CvO) cm21; H NMR d 2.16 5m, 2H, Hs-2), 2.53 5dd,
2H, J6.9, 6.5 Hz, Hs-3), 3.63 5t, 2H, J6.2 Hz, Hs-1),
7.53 5m, 2H, H-9, H-10), 7.81 5d, 1H, J8.5 Hz, H-6),
7.92 5m, 1H, H-8), 8.22 5d, 1H, J8.5 Hz, H-5), 8.40 5m,
1H, H-11); 13C NMR d 23.3 5C-2), 29.4 5C-1), 38.8 5C-3),
121.6 5C-6), 123.8 5C-8), 125.4 5C-10), 125.8 5C-5), 126.0
5C-11), 127.0 5C-9), 130.6 5C-6a), 133.7 5C-7a), 136.7
5C-11b), 140.6 5C-11a), 142.4 5C-4a), 146.1 5C-11c),
198.7 5C-4);MS m/e 5rel. int.) 76 58), 98 516), 152 525),
196 560), 224 563), 252 5M1, 100).
2H, J7.1, 6.6 Hz, Hs-3), 2.86 5m, 2H, Hs-5), 2.95 5m,
2H, Hs-6), 2.99 5m, 2H, Hs-1), 7.27 5m, 2H, H-9, H-10),
7.50 5m, 1H, H-8), 7.67 5m, 1H, H-11); 13C NMR d 20.8
5C-5), 21.9 5C-6), 22.4 5C-2), 27.5 5C-1), 37.5 5C-3), 111.8
5C-8);114.4 5C-11a), 119.9 5C-11), 123.6 5C-10), 123.9
5C-9), 125.3 5C-11b), 125.8 5C-4a), 49.1 5C-11c), 155.5
5C7a), 160.6 5C-6a), 197.5 5C-4);MS m/e 5rel. int.) 76
516), 152 530), 181 586), 208 545), 221 527), 238 5M1, 100).
4.1.6. 2,3-Dihydronaphtho[2,1-b]benzo[b]furan-451H)-
one 58a). When the mixture obtained from the cycloaddition
reaction between 1a and 2 5entry 1ÐTable 1) was treated
with DBN 50.42 mL) in dry THF 59 mL) for 36 h at room
temperature, crude 8a was obtained. It was chromato-
graphed 5SiO2, hexane/ethyl acetate 4:1) to afford the title
compoud 8a 542% overall yield) as a pale yellow micro-
crystalline solid, mp 100±1018C 54:1 hexane/ethyl acetate);
5found: C, 81.2;H, 5.1. C 16H12O2 requires C, 81.34;H,
4.1.9. DDQ oxidation of compounds 7. A benzene solution
53 mL) of ketone 7a or 7b 51.2 mmol), and DDQ 50.6 g),
was heated at re¯ux temperature for 1 h under nitrogen.
After cooling, the reaction mixture was diluted with ben-
zene 510 mL), washed with 10% aqueous Na2S2O4 solution,
10% aqueous KOH solution and saturated brine.
Drying 5Na2SO4), ®ltration and concentration in vacuo of
the solvent afforded a residue which was chromatographed
on silica gel. Elution with 95:5 hexane/ethyl acetate gave
pure 8a 598%) or 8b 599%).
1
5.12%);IR 1676 5s, C vO) cm21; H NMR d 2.35 5m,
2H, Hs-2), 2.77 5dd, 2H, J6.5, 6.3 Hz, Hs-3), 3.50 5t,
2H, J6.2 Hz, Hs-1), 7.41 5ddd, 1H, J7.8, 7.3, 1.0 Hz,
H-10), 7.50 5d, 1H, J8.7 Hz, H-6), 7.51 5ddd, 1H, J8.3,
7.3, 1.4 Hz, H-9), 7.62 5dd, 1H, J8.3, 1.0 Hz, H-8), 8.06
5dd, 1H, J7.8, 1.4 Hz, H-11), 8.24 5d, 1H, J8.7 Hz, H-5);
13C NMR d 22.9 5C-2), 27.2 5C-1), 38.6 5C-3), 110.3 5C-6),
112.0 5C-8), 122.0 5C-11b), 122.4 5C-11), 123.4 5C-10),
124.2 5C-11a), 127.2 5C-9), 127.3 5C-5);128.3 5C-4a),
140.9 5C-11c), 156.7 5C-7a), 158.9 5C-6a), 197.4 5C-4);
4.1.10. Tetracyclic hydrocarbons 9. A 1:1 methanol±
dichloromethane solution 520 mL) of ketone 7a or 7b
51.3 mmol) and NaBH4 50.31 g) was stirred for 2 h at
room temperature. The reaction mixture was then worked
up as usual and the crude product was dissolved in triglyme
510 mL) and treated with 10% Pd±C catalyst 50.3 g) at
re¯ux temperature for 24 h. Usual work up afforded a