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V.Yu. Korotaev et al. / Tetrahedron 66 (2010) 1404–1409
7.05–7.10 (m, 2H, H-8, H-10), 7.16 (dd, 1H, H-11, J¼8.0, 1.5 Hz), 7.27
(td, 1H, H-9, J¼7.5, 1.5 Hz). Anal. Calcd for C14H12Cl3NO4: C, 46.12; H,
3.32; N, 3.84. Found: C, 46.14; H, 3.31; N, 3.73.
3.84 (dt,1H, H-2, J¼8.6, 7.5 Hz), 4.14 (td,1H, H-20, J¼8.6, 6.0 Hz), 4.15
(br d,1H, H-11b, J¼5.0 Hz), 5.79 (d,1H, H-6, J¼1.4 Hz), 6.11 (d,1H, H-
3a, J¼7.1 Hz), 6.66 (d, 1H, H-11, J¼2.9 Hz), 6.81 (dd, 1H, H-9, J¼8.9,
2.9 Hz), 7.01 (d, 1H, H-8, J¼8.9 Hz). Anal. Calcd for C15H14Cl3NO5: C,
45.65; H, 3.58; N, 3.55. Found: C, 45.61; H, 3.58; N, 3.46.
4.2.5. 3a,11c-cis-6,11b-trans-11b,11c-cis-10-Bromo-6-tri-
chloromethyl-1,2,11b,11c-tetrahydro-3aH,6H-chromeno[3,4-
c]furo[3,2-e][1,2]oxazin-5-oxide (2e). Yield 49%, mp 205–206 ꢀC
(decomp., CH2Cl2–hexane, 1:2); IR (KBr) 1608, 1578, 1480,
4.3. General procedure for the synthesis of fused
chromans (3a–c)
1371 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d
1.62 (dq, 1H, H-1, J¼13.3,
7.6 Hz), 1.80 (dddd, 1H, H-10, J¼13.3, 9.7, 7.6, 5.6 Hz), 3.34 (dtd, 1H,
H-11c, J¼9.7, 7.3, 5.3 Hz), 3.85 (dt, 1H, H-2, J¼9.0, 7.4 Hz), 4.15 (ddd,
1H, H-20, J¼9.0, 7.9, 5.6 Hz), 4.18 (br d, 1H, H-11b, J¼5.0 Hz), 5.84 (d,
1H, H-6, J¼1.4 Hz), 6.11 (d, 1H, H-3a, J¼7.0 Hz), 6.98 (d, 1H, H-8,
J¼8.7 Hz), 7.30 (d, 1H, H-11, J¼2.3 Hz), 7.37 (dd, 1H, H-9, J¼8.7,
A mixture of the corresponding chromene 1 (2.0 mmol) and
ethyl vinyl ether (0.29 g, 4.0 mmol) was kept at 40 ꢀC for the ap-
propriate time in a sealed tube (Table 2). The resulting reaction
mixture was concentrated under reduced pressure and the solid
product obtained at standing was recrystallized from CH2Cl2–hex-
ane (1:2) to give compounds 3 as colorless crystals.
2.3 Hz); 13C NMR (100 MHz, CDCl3)
d 26.35 (C-1), 34.74 (C-11b),
46.69 (C-11c), 68.53 (C-2), 79.04 (C-6), 98.92 (CCl3), 108.00 (C-3a),
115.85 (C-10), 117.81 (C-5a), 119.96 (C-8), 123.17 (C-11a), 130.10 (C-
11), 132.37 (C-9), 150.77 (C-7a). Anal. Calcd for C14H11BrCl3NO4: C,
37.91; H, 2.50; N, 3.16. Found: C, 37.86; H, 2.57; N, 3.09.
4.3.1. 2,10b-cis-5,10b-trans-2-Ethoxy-5-trichloromethyl-1,10b-dihy-
dro-2H,5H-chromeno[3,4-c][1,2]oxazin-4-oxide (3a). Yield 15%, mp
126–127 ꢀC; IR (KBr) 1608, 1587, 1492, 1456, 1368 cmꢁ1 1H NMR
;
(400 MHz, CDCl3)
d
1.23 (t, 3H, Me, J¼7.1 Hz), 2.02 (ddd, 1H, H-1,
4.2.6. 3a,11c-cis-6,11b-trans-11b,11c-cis-6-Trichloromethyl-10-nitro-
1,2,11b,11c-tetrahydro-3aH,6H-chromeno[3,4-c]furo[3,2-e][1,2]ox-
azin-5-oxide (2f). Yield 40%, mp 231–232 ꢀC (decomp.); IR (KBr)
J¼13.8, 10.6, 5.3 Hz), 2.88 (ddd, 1H, H-10, J¼13.8, 7.3, 5.9 Hz), 3.68
(dq, 1H, OCHH, J¼9.5, 7.1 Hz), 4.03–4.11 (m, 2H, OCHH, H-10b), 5.58
(t, 1H, H-2, J¼5.6 Hz), 5.95 (d, 1H, H-5, J¼1.1 Hz), 7.00–7.05 (m, 2H,
H-7, H-9), 7.10 (br d, 1H, H-10, J¼7.5 Hz), 7.23 (td, 1H, H-8, J¼7.8,
1.7 Hz). Anal. Calcd for C14H14Cl3NO4: C, 45.87; H, 3.85; N, 3.82.
Found: C, 45.80; H, 3.91; N, 3.78.
1651, 1619, 1582, 1522, 1478, 1343, 1331 cmꢁ1 1H NMR (400 MHz,
;
CDCl3)
d
1.58 (dq, 1H, H-1, J¼13.2, 7.8 Hz), 1.78 (dddd, 1H, H-10,
J¼13.2, 9.7, 7.5, 5.3 Hz), 3.44 (dtd, 1H, H-11c, J¼9.7, 7.5, 5.3 Hz), 3.86
(dt,1H, H-2, J¼9.1, 7.5 Hz), 4.17 (ddd,1H, H-20, J¼9.0, 8.1, 5.2 Hz), 4.35
(br d,1H, H-11b, J¼5.0 Hz), 5.97 (d,1H, H-6, J¼1.4 Hz), 6.16 (d,1H, H-
3a, J¼7.0 Hz), 7.23 (d, 1H, H-8, J¼8.9 Hz), 8.15 (d, 1H, H-11, J¼2.7 Hz),
8.18 (dd, 1H, H-9, J¼8.9, 2.7 Hz). Anal. Calcd for C14H11Cl3N2O6: C,
41.05; H, 2.71; N, 6.84. Found: C, 40.89; H, 2.67; N, 6.75.
4.3.2. 2,10b-cis-5,10b-trans-2-Ethoxy-9-nitro-5-trichloromethyl-
1,10b-dihydro-2H,5H-chromeno[3,4-c][1,2]oxazin-4-oxide (3b). Yield
35%, mp 164–165 ꢀC; IR (KBr) 1624, 1586, 1520, 1479, 1376,
1339 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d
1.24 (t, 3H, Me, J¼7.1 Hz),
2.27 (ddd, 1H, H-1, J¼12.9, 12.2, 2.8 Hz), 3.35 (ddd, 1H, H-10, J¼12.9,
7.5, 7.0 Hz), 3.73 (dq, 1H, OCHH, J¼9.5, 7.1 Hz), 3.95 (ddq, 1H, H-10b,
J¼12.2, 7.0, 1.0 Hz), 4.07 (dq, 1H, OCHH, J¼9.5, 7.1 Hz), 5.69 (dd, 1H,
H-2, J¼7.6, 2.8 Hz), 5.98 (d, 1H, H-5, J¼1.0 Hz), 7.21 (d, 1H, H-7,
J¼9.0 Hz), 8.06 (dd, 1H, H-10, J¼2.7, 1.3 Hz), 8.17 (ddd, 1H, H-8,
4.2.7. 3a,11c-cis-6,11b-trans-11b,11c-cis-6-Trichloromethyl-8-nitro-
1,2,11b,11c-tetrahydro-3aH,6H-chromeno[3,4-c]furo[3,2-e][1,2]oxazin-
5-oxide (2g). Yield 30%, mp 199–200 ꢀC (decomp., CH2Cl2–hexane,
1:2); IR (KBr) 1620, 1588, 1528, 1460, 1369 cmꢁ1; 1H NMR (400 MHz,
CDCl3) (endo-isomer, 85%)
d
1.68 (dq, 1H, H-1, J¼13.1, 7.5 Hz), 1.80
J¼9.0, 2.7, 1.0 Hz); 13C NMR (100 MHz, CDCl3)
d 14.72 (Me), 31.06 (C-
(dddd, 1H, H-10, J¼13.1, 9.6, 7.5, 5.3 Hz), 3.38 (dtd, 1H, H-11c, J¼9.6,
7.0, 5.3 Hz), 3.87 (dt,1H, H-2, J¼9.0, 7.4 Hz), 4.18 (ddd,1H, H-20, J¼9.0,
8.1, 5.7 Hz), 4.33 (br d, 1H, H-11b, J¼5.1 Hz), 6.00 (d, 1H, H-6,
J¼1.4 Hz), 6.15 (d, 1H, H-3a, J¼7.0 Hz), 7.22 (t, 1H, H-10, J¼7.9 Hz),
7.43 (br d, 1H, H-11, J¼7.8 Hz), 7.84 (dd, 1H, H-9, J¼8.1, 1.4 Hz); (exo-
10b), 36.31 (C-1), 65.63 (OCH2), 79.86 (C-5), 99.42 (CCl3), 104.20 (C-
2), 118.36 (C-4a), 118.87 (C-7), 121.73 (C-10), 122.73 (C-10a), 124.86
(C-8), 143.48 (C-9), 156.37 (C-6a). Anal. Calcd for C14H13Cl3N2O6: C,
40.85; H, 3.18; N, 6.81. Found: C, 41.00; H, 3.38; N, 6.82.
isomer, 15%)
d
2.12–2.28 (m, 2H, 2-CH2), 3.80–3.88 (m, 1H, H-11c),
4.3.3. 2,10b-cis-5,10b-trans-2-Ethoxy-7,9-dinitro-5-(trichloro-
methyl)-1,10b-dihydro-2H,5H-chromeno[3,4-c][1,2]oxazin-4-oxide
(3c). Yield 46%, mp 172–173 ꢀC (yellow powder); IR (KBr) 1630,
4.02 (td,1H, H-2, J¼8.8, 4.6 Hz), 4.14 (m,1H, H-11b), 4.28 (q,1H, H-20,
J¼8.5 Hz), 5.98 (d, 1H, H-6, J¼1.2 Hz), 6.22 (d, 1H, H-3a, J¼7.3 Hz),
7.25 (t, 1H, H-10, J¼7.9 Hz), 7.45 (dt, 1H, H-11, J¼7.8, 1.3 Hz), 7.83 (dd,
1H, H-9, J¼8.1, 1.4 Hz). Anal. Calcd for C14H11Cl3N2O6: C, 41.05; H,
2.71; N, 6.84. Found: C, 40.84; H, 2.58; N, 6.70.
1615, 1600, 1541, 1524, 1335 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d 1.24
(t, 3H, Me, J¼7.1 Hz), 2.32 (td, 1H, H-1, J¼12.4, 2.8 Hz), 3.40 (dt, 1H,
H-10, J¼12.8, 7.3 Hz), 3.74 (dq, 1H, OCHH, J¼9.6, 7.1 Hz), 4.02 (dddt,
1H, H-10b, J¼12.1, 7.1, 1.3, 1.0 Hz), 4.07 (dq, 1H, OCHH, J¼9.6, 7.1 Hz),
5.72 (dd, 1H, H-2, J¼7.5, 2.8 Hz), 6.14 (d, 1H, H-5, J¼1.0 Hz), 8.24 (dd,
1H, H-10, J¼2.7, 1.3 Hz), 8.68 (dd, 1H, H-8, J¼2.7, J¼1.0 Hz); 13C NMR
4.2.8. 3a,11c-cis-6,11b-trans-11b,11c-cis-6-Trichloromethyl-8,10-di-
nitro-1,2,11b,11c-tetrahydro-3aH,6H-chromeno[3,4-c]furo[3,2-
e][1,2]oxazin-5-oxide (2h). Yield 56%, mp 219–220 ꢀC (decomp.); IR
(100 MHz, CDCl3)
d 14.68 (Me), 31.21 (C-10b), 36.63 (C-1), 65.85
(KBr) 1617, 1598, 1537, 1464, 1375, 1341 cmꢁ1
;
1H NMR (400 MHz,
(OCH2), 80.23 (C-5), 98.73 (CCl3), 104.07 (C-2), 116.37 (C-4a), 120.47
(C-8), 124.41 (C-10), 126.52 (C-10a), 139.86 (C-7), 141.97 (C-9),
149.46 (C-6a). Anal. Calcd for C14H12Cl3N3O8: C, 36.83; H, 2.65; N,
9.20. Found: C, 36.79; H, 2.64; N, 9.06.
DMSO-d6)
d
1.43 (dq, 1H, H-1, J¼12.7, 7.7 Hz), 1.71–1.80 (m, 1H, H-
10), 3.67–3.74 (m, 1H, H-11c), 3.76 (dt, 1H, H-2, J¼8.4, 7.5 Hz), 4.03
(td, 1H, H-20, J¼8.4, 5.5 Hz), 4.72 (br d, 1H, H-11b, J¼5.1 Hz), 6.19 (d,
1H, H-3a, J¼6.9 Hz), 6.49 (d, 1H, H-6, J¼1.2 Hz), 8.70 (d, 1H, H-11,
J¼2.6 Hz), 8.82 (d,1H, H-9, J¼2.6 Hz). Anal. Calcd for C14H10Cl3N3O8:
C, 36.99; H, 2.22; N, 9.24. Found: C, 36.92; H, 2.45; N, 9.05.
4.4. 2,6-Diethoxy-12-nitro-8-(trifluoromethyl)-1,6,7,13b-
tetrahydro-2H-chromeno[3,4-c]isoxazolo[2,3-b][1,2]oxazine (4)
4.2.9. 3a,11c-cis-6,11b-trans-11b,11c-cis-10-Methoxy-6-trichloro-
methyl-1,2,11b,11c-tetrahydro-3aH,6H-chromeno[3,4-c]furo[3,2-
e][1,2]oxazin-5-oxide (2i). Yield 49%, mp 217–218 ꢀC; IR (KBr) 1610,
A mixture of chromene 1c (0.58 g, 2.0 mmol) and ethyl vinyl
ether (0.29 g, 4.0 mmol) was kept at 60 ꢀC for 3 h in a sealed tube.
The resulting reaction mixture was concentrated under reduced
pressure and the solid product that formed was recrystallized from
CH2Cl2–hexane (1:2) to give compound 4 as colorless crystals.
Yield 0.42 g (48%), mp 148–149 ꢀC; IR (KBr) 1590, 1528, 1487, 1449,
1600,1499,1464, 1373,1326 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d 1.68
(dq, 1H, H-1, J¼13.5, 7.5 Hz), 1.78 (dddd, 1H, H-10, J¼13.5, 9.7, 7.5,
6.0 Hz), 3.34 (dtd, 1H, H-11c, J¼9.7, 7.1, 5.3 Hz), 3.79 (s, 3H, MeO),