628
HETEROCYCLES, Vol. 80, No. 1, 2010
hydrogen gas. The resulting solution was filtered through Celite, and the residue upon evaporation of the
solvent was chromatographed with hexane-AcOEt (85:15, v/v) as eluent to give the
2-hydroxyphenethyl-substituted tetramethoxybenzene 2 (924.7 mg, 94%) as colorless prisms; mp
1
104.9–107.2 ˚C (AcOEt/hexane); IR (KBr): 3357, 1592, 1460, 1226 cm−1; H-NMR (400 MHz, CDCl3)
2.70–2.74 (m, 2H), 2.82–2.86 (m, 2H), 3.86 (s, 6H), 3.88 (s, 6H), 6.47 (s, 1H), 6.58 (s, 1H), 6.85 (dt, J
13
= 1.2, 7.2 Hz, 1H), 6.92 (d, J = 7.2 Hz, 1H), 7.13-7.17 (m, 2H); C-NMR (100 MHz, CDCl3) 25.4
(CH2), 32.3 (CH2), 56.3 (CH3), 61.3 (CH3), 97.2 (CH), 115.8 (CH), 120.1 (CH), 127.1 (Cq), 127.9 (CH),
129.4 (Cq), 129.8 (CH), 140.5 (Cq), 149.0 (Cq), 154.7 (Cq); HRMS (ESI) m/z calcd for C18H22O5Na
[M++Na+] 341.1365, found 341.1356.
1,4,4a-Trimethoxy-10,11-dihydrodibenzo[b,f]oxepin-2(4aH)-one (4)
To a stirred solution of the 2-hydroxyphenethyl-substituted tetramethoxybenzene 2 (50 mg, 0.16 mmol)
in dioxane (4 mL) was added DDQ (178 mg, 0.79 mmol) in portions at rt. After the reaction mixture was
stirred at the same temperature for 10 h, the solvent was evaporated under reduced pressure. The residue
was chromatographed on silica gel with hexane-AcOEt (70:30 v/v) as eluent to give tricyclic quinone
monoacetal 4 (38.5 mg, 81%) as colorless prisms; mp 137.6–138.5 ˚C (AcOEt/hexane); IR (KBr): 3442,
1
2937, 1637, 1458, 1232 cm−1; H-NMR (400 MHz, CDCl3) 2.34–2.42 (m, 1H), 2.73–2.81 (m, 1H),
13
3.11–3.24 (m, 5H), 3.59 (s, 3H), 3.91 (s, 3H), 5.61 (s, 1H), 6.95–7.15 (m, 4H); C-NMR (100 MHz,
CDCl3) 22.2 (CH2), 29.8 (CH2), 51.9 (CH3), 56.4 (CH3), 60.8 (CH3), 98.7 (Cq), 103.1 (CH), 122.7 (CH),
125.1 (CH), 127.5 (CH), 129.0 (CH), 134.4 (Cq), 136.4 (Cq), 150.6 (Cq), 151.9 (Cq), 169.1 (Cq), 182.0
(Cq); HRMS (ESI) m/z calcd for C17H19O5 [M++H+] 303.1232, found 303.1231.
X-Ray crystallographic analysis of compound 4.6 A colorless block crystal having approximate
dimensions of 0.60 x 0.60 x 0.40 mm was mounted on a glass fiber. All measurements were made on a
Rigaku RAXIS RAPID imaging plate area detector with graphite monochromated Mo-K radiation. The
structure was solved by direct methods (SIR97) and expanded using Fourier techniques (DIRDIF99). The
non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined using the riding model.
The final cycle of full-matrix least-squares refinement on F was based on 13,033 observed reflections (I >
0.00(I)) and 218 variable parameters, and converged (largest parameter shift was 0.54 times its esd) with
unweighted and weighted agreement factors of R = 0.043 and R = 0.110. Crystal data for 4: C17H18O5,
w
M = 302.33, monoclinic, space group P21/n, a = 13.6538(8) Å, b = 8.4884(4) Å, c = 13.9424(9) Å, =
113.237(2)º, V = 1484.8(1) Å3, Z = 4, Dc = 1.352 g/cm3, F(000) = 640, (MoK) = 0.99 cm–3.