S. R. Taylor et al. / Tetrahedron 63 (2007) 11377–11385
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according to oxidative coupling method B. Mp 122–124 ꢀC.
1H NMR: d 7.20 (t, 2H, J¼8.1 Hz, Ar–H-50), 6.97 (s, 2H,
Ar–H-6), 6.79 (s, 2H, Ar–H-3), 6.74 (dd, 2H, J¼8.1,
2.1 Hz, Ar–H-60), 6.54 (dd, 2H, J¼8.1, 2.1 Hz, Ar–H-40),
6.50 (t, 2H, J¼2.1 Hz, Ar–H-20), 3.94 (s, 6H, OCH3-4),
3.79 (s, 6H, OCH3-3), 3.73 (s, 6H, OCH3-30), 3.62 (ABq,
4H, J¼16.2 Hz, Ar–CH2). 13C NMR: d 170.3 (C]O),
160.3 (Ar–C–OCH3-30), 151.5 (Ar–C-10), 148.4 (Ar–C–
OCH3-3), 147.7 (Ar–C–OCH3-4), 132.9 (Ar–C-1), 129.6
(Ar–C–H-50), 124.3 (Ar–C-2), 113.5 (Ar–C–H-5), 113.4
(Ar–C–H-40), 112.7 (Ar–C–H-2), 111.5 (Ar–C–H-60),
107.4 (Ar–C–H-20), 55.9 (Ar–OCH3-4), 55.8 (Ar–OCH3-
3), 55.2 (Ar–OCH3-30), 38.3 (Ar–CH2–CO). MS (EI+): m/z
602 (M+, 10%), 299 (100%). HRMS (EI+) calcd for
C34H34O10: 602.2151 (M+), found: 602.2160.
4.3.10. Dimethyl 2,20-(4,40,5,50-tetramethoxybiphenyl-
2,20-diyl)diacetate 6.38 The title compound was prepared
in 41% yield (clear crystals, 53 mg) from 5 (129 mg,
0.62 mmol) in the presence of PIFA (250 mg, 0.58 mmol),
BF3$Et2O (150 mL) and MeCN (10 mL) according to oxida-
tive coupling method A. Mp 142–144 ꢀC (lit.38 mp 145 ꢀC).
1H NMR: d 6.84 (s, 2H, Ar–H-6), 6.72 (s, 2H, Ar–H-3), 3.92
(s, 6H, OCH3-5), 3.83 (s, 6H, OCH3-4), 3.60 (s, 6H,
CO2CH3), 3.35 (ABq, 4H, J¼16.5 Hz, Ar–CH2). 13C
NMR: d 172.4 (C]O), 148.1 (Ar–C–OCH3-4), 147.4 (Ar–
C–OCH3-5), 132.8 (Ar–C-1), 124.6 (Ar–C-2), 113.2
(Ar–C–H-3), 112.5 (Ar–C–H-6), 55.8 (Ar–OCH3), 55.7
(Ar–OCH3), 51.8 (CO2CH3), 37.9 (Ar–CH2). MS (CI+): m/z
419 (M+H, 100%). HRMS (EI+) calcd for C22H26O8:
418.1627 (M+), found: 418.1615.
4.3.8. Di-(4-methoxyphenyl)-2,20-(4,40,5,50-tetramethoxy-
biphenyl-2,20-diyl)diacetate 3d. The title compound was
prepared in 50% yield (white solid, 49.5 mg) from 1d
(100 mg, 0.28 mmol) in the presence of PIFA (149 mg,
0.34 mmol), BF3$Et2O (83 mL) and MeCN (5 mL) accord-
ing to oxidative coupling method A. The title compound
was also prepared in 63% yield (clear film, 49.5 mg) from
1d (50 mg, 0.14 mmol) in the presence of TTFA (44 mg,
0.082 mmol), BF3$Et2O (100 mL) and MeCN (1 mL) ac-
cording to oxidative coupling method B. Mp 102–104 ꢀC.
1H NMR: d 6.97 (s, 2H, Ar–H-6), 6.86 (d, 4H, J¼9.0 Hz,
Ar–H-20, 60), 6.82 (d, 4H, J¼9.0 Hz, Ar–H-30, 50), 6.79 (s,
2H, Ar–H-3), 3.95 (s, 6H, OCH3), 3.79 (s, 6H, OCH3),
3.77 (s, 6H, OCH3), 3.59 (ABq, 4H, J¼16.2 Hz, Ar–CH2).
13C NMR: d 170.8 (C]O), 157.1 (Ar–C–OCH3-40), 148.3
(Ar–C–OCH3-5), 147.6 (Ar–C–OCH3-4), 144.0 (Ar–C–10),
132.9 (Ar–C-1), 124.3 (Ar–C-2), 122.1 (2ꢂAr–C–H-20,
60), 114.2 (2ꢂAr–C–H-30, 50), 113.3 (Ar–C–H-3), 112.6
(Ar–C–H-6), 55.9 (Ar–OCH3), 55.8 (Ar–OCH3), 55.4 (Ar–
OCH3), 38.2 (Ar–CH2–CO). MS (EI+): m/z 602 (M+, 2%).
HRMS (EI+) calcd for C34H34O10: 602.2151 (M+), found:
602.2182.
4.3.11. 4,5-Dimethoxy-2-(4-methoxy-3,6-dioxocyclohexa-
1,4-dien-1-yl)phenyl acetate 8. The title compound was
prepared in 70% yield (cloudy film, 49 mg) from 7 (100 mg,
0.51 mmol) in the presence of PIFA (227 mg, 0.53 mmol),
BF3$Et2O (130 mL) and MeCN (5 mL) according to oxidative
coupling method A. The title compound was also prepared in
62% yield (clear film, 44 mg) from 3,4-dimethoxyphenyl-
acetate (100 mg, 0.51 mmol) in the presence of TTFA
(44 mg, 0.082 mmol), BF3$Et2O (100 mL) and MeCN (1 mL)
according to oxidative coupling method B. 1H NMR:
d 6.75 (s, 1H, Ar–H-3), 6.73 (s, 1H, Ar–H-6), 6.72 (s, 1H,
Q–H-b), 6.03 (s, 1H, Q–H-e), 3.89 (s, 3H, –OCH3-5), 3.87
(s, 3H, OCH3-4), 3.86 (s, 3H, Q–OCH3), 2.16 (s, 3H,
COCH3). 13C NMR: d 185.4 (Q–C]O-c), 181.8 (Q–C]
O-f), 168.9 (C]O), 158.4 (Q–C–OCH3), 150.6 (Ar–C–
OCH3-5), 146.5 (Ar–C–OCH3-4), 144.2 (Ar–C-1), 142.1
(Q–C-a), 132.2 (Q–C–H-b), 117.1 (Ar–C-2), 112.8 (Ar–C–
H-3), 107.7 (Q–C–H-e), 106.6 (Ar–C–H-6), 56.2 (Ar–OCH3-
5), 56.1 (Ar–OCH3-4), 56.0 (Q–OCH3), 20.8 (COCH3).
MS (EI+): m/z 332 (M+, 16%), 292 (100%). HRMS (EI+)
calcd for C17H16O7: 332.0896 (M+), found: 332.0896.
4.3.12. 4,5-Dimethoxy-2-(4-methoxy-3,6-dioxocyclohexa-
1,4-dien-1-yl)phenyl 3,4-dimethoxybenzoate 12a. The
title compound was prepared in 98% yield (red crystals,
55 mg) from 11a (79 mg, 0.25 mmol) in the presence of
PIFA (112 mg, 0.26 mmol), BF3$Et2O (63 mL) and DCM
(5 mL) according to oxidative coupling method A. Mp
4.3.9. 4,5-Dimethoxy-2-(4-methoxy-3,6-dioxocyclohexa-
1,4-dien-1-yl)phenyl (3-methoxyphenyl)acetate 4e. The
title compound was prepared in 38% yield (pale film,
34 mg) from 3,4-dimethoxyphenyl (3-methoxyphenyl)ace-
tate 1e (123 mg, 0.41 mmol) in the presence of PIFA
(184 mg, 0.43 mmol), BF3$Et2O (104 mL) and MeCN
(5 mL) according to oxidative coupling method A. 1H
NMR: d 7.16 (t, 1H, J¼7.8 Hz, Ar–H-5), 6.82 (dd, 1H,
J¼7.8, 2.7 Hz, Ar–H-6), 6.79 (d, 1H, J¼2.1 Hz, Ar–H-2),
6.76 (dd, 1H, J¼7.8, 2.7 Hz, Ar–H-4), 6.71 (s, 1H, Ar–H-
60), 6.65 (s, 1H, Ar–H-30), 6.52 (s, 1H, Q–H-b), 5.78 (s,
1H, Q–H-e), 3.87 (s, 3H, OCH3-50), 3.83 (s, 3H, OCH3-40),
3.81 (s, 3H, OCH3-3), 3.77 (s, 3H, Q–OCH3), 3.66 (s, 2H,
Ar–CH2). 13C NMR: d 185.5 (Q–C]O-c), 181.4 (Q–C]
O-f), 169.3 (C]O), 159.6 (Ar–C–OCH3-3), 158.0 (Q–C–
OCH3-d), 150.5 (Ar–C–OCH3-40), 146.7 (Ar–C–OCH3-50),
144.0 (Ar–C-10), 141.8 (Q–C-a), 134.2 (Ar–C-1), 132.4
(Q–C–H-b), 129.7 (Ar–C–H-5), 121.5 (Ar–C–H-6), 117.4
(Ar–C-20), 114.5 (Ar–C–H-2), 113.1 (Ar–C–H-4), 112.5
(Ar–C–H-30), 107.5 (Q–C–H-e), 106.4 (Ar–C–H-60),
56.2 (Ar–OCH3-40), 56.1 (Ar–OCH3-50), 56.0 (Ar–OCH3-
3), 55.1 (Q–OCH3), 41.3 (Ar–CH2). MS (EI+): m/z 438
(M+, 16%), 292 (100%). HRMS (EI+) calcd for C24H22O8:
438.1314 (M+), found: 438.1331.
1
196–198 ꢀC. H NMR: d 7.71 (dd, 1H, J¼8.7, 2.1 Hz, Ar–
H-6), 7.54 (d, 1H, J¼2.1 Hz, Ar–H-2), 6.91 (d, 1H,
J¼8.7 Hz, Ar–H-5), 6.84 (s, 1H, Ar–H-60), 6.81 (s, 1H,
Ar–H-30), 6.79 (s, 1H, Q–H-b), 5.94 (s, 1H, Q–H-e), 3.95
(s, 3H, OCH3), 3.93 (s, 3H, OCH3), 3.91 (s, 3H, OCH3),
3.90 (s, 3H, OCH3), 3.79 (s, 3H, Q–OCH3). 13C NMR:
d 185.5 (Q–C]O-c), 181.7 (Q–C]O-f), 164.4 (C]O),
158.3 (Q–C–OCH3), 153.6 (Ar–C–OCH3-3), 150.7 (Ar–C–
OCH3-40), 148.7 (Ar–C–OCH3-4), 146.6 (Ar–C–OCH3-50),
144.3 (Ar–C-10), 142.5 (Q–C-a), 132.5 (Q–C–H-b), 124.3
(Ar–C–H-6), 121.1 (Ar–C-1), 117.4 (Ar–C-20), 112.8 (Ar–
C–H-30), 112.2 (Ar–C–H-2), 110.4 (Ar–C–H-5), 107.7
(Q–C–H-e), 106.7 (Ar–C–H-60), 56.3 (Ar–OCH3), 56.2
(Ar–OCH3), 56.1 (Ar–OCH3), 56.0 (Ar–OCH3), 55.9 (Q–
OCH3). MS (EI+): m/z 454 (M+, 2%). HRMS (EI+) calcd
for C24H22O9: 454.1263 (M+), found: 454.1256.
4.3.13. 4,5-Dimethoxy-2-(4-methoxy-3,6-dioxocyclohexa-
1,4-dien-1-yl)phenyl 2,3,4-trimethoxybenzoate 12b. The