Sarma and Jones
JOCArticle
the favored pathway. The pathways provide potential for
synthetic application in natural product synthesis and a
mechanism to produce diradicals using visible light. More
work is needed to understand how substituents and medium
direct the reaction down a particular pathway, so that
synthetically significant yields can be reliably obtained.
Photolysis of 11. A solution of 1153 (200 mg, 0.476 mmol) in
200 mL of benzene was irradiated using method B for 40 h. Flash
column chromatography with a hexane/EtOAc gradient gave
the following products:
1-(Benzyloxy)-4-hydroxy-9,10-anthraquinone (22). Compound
22 was obtained as a brick red solid and recrystallized from
hexanes/EtOAc to give 47.2 mg (0.143 mmol, 30%): mp 137-
138 °C; IR (KBr) 3064, 3031, 2864, 1662, 1632, 1593, 1570, 1475,
1442, 1429, 1352, 1237, 1169, 1041, 1071, 830, 787, 725 cm-1; 1H
NMR (300 MHz, CDCl3) δ 13.00 (s, 1H), 8.29 (dt, 2H, J = 7.6,
1.4 Hz), 7.82-7.72 (m, 2H), 7.58 (d, 2H, J = 7.3 Hz), 7.43-7.24
(m, 6H), 5.30 (s, 2H); 13C NMR (75 MHz, CDCl3) δ 187.6, 180.2,
156.9, 152.1, 135.7, 134.3, 134.0, 132.6, 131.7, 128.1, 127.4, 126.8,
126.5, 125.9, 125.8, 125.5, 119.9, 115.6, 72.2; HRMS (EI) calcd for
C21H14O4 Naþ [M þ Na]þ 353.078430, found 353.078143.
2-Benzyl-4-(benzyloxy)-1-hydroxy-9,10-anthraquinone (23).
Compound 23 was obtained as an orange solid (40 mg, 0.095
mmol, 20%): mp 169-171 °C; IR (KBr) 3433, 3027, 2918, 1661,
1630, 1588, 1427, 1348, 1262, 1243, 1008, 814, 799, 738 cm-1; 1H
NMR (300 MHz, CDCl3) δ 13.52 (s, 1H), 8.30 (m, 2H),
7.83-7.72 (m, 2H), 7.45-7.27 (m, 8H), 7.18-7.16 (m, 2H), 7.1
(s, 1H), 5.18 (s, 2H), 4.10 (s, 2H); 13C NMR (75 MHz, CDCl3) δ
189.2, 181.3, 156.3, 152.6, 139.7, 138.3, 136.4, 135.1, 134.7,
133.2, 132.4, 129.2, 128.7, 128.6, 127.9, 127.3, 127.2, 126.6,
126.4, 126.3, 118.5, 115.4, 71.7, 35.8; HRMS (EI) calcd for
C28H20O4 Naþ [M þ Na]þ 443.125380, found 443.125221.
10-Benzyl-4-(benzyloxy)-1,10-dihydroxyanthracen-9(10H)-one (24).
Compound 24 was obtained as an orange solid (44.2 mg, 0.104 mmol,
22%): mp 118-119 °C; IR (KBr) 3090, 3065, 3026, 2854, 1640, 1599,
Experimental Section
General Procedure for Relative Photolysis Rates (Method A).
Solutions of anthraquinone were prepared in 1:1 CD3OD/
DMSO-d6. A solution of anthraquinone was then photolyzed
alongside a control solution of 10 with equal A405. Each solution
was irradiated in borosilicate NMR tubes using a monochro-
mator set to 405 nm with a 10 nm bandpass in conjunction with a
focused 150 W Hg/Xe lamp. The disappearance of the 1-benzy-
1
loxymethylene H NMR signal was followed over time. Each
experiment was repeated at least three times.
General Procedure for Preparative Photochemical Reactions
(Method B). A solution of anthraquinone was prepared in the
solvent of choice (methanol, hexane, or benzene) and Ar was
passed through the solution for 2 h to remove oxygen. The
solution was photolyzed in a Rayonet photoreactor fitted with
eight lamps with peak emission at 419 nm. The reaction was
followed by TLC and stopped when the starting material was
found to be completely consumed. Solvent was removed in
vacuo and the crude product analyzed by 1H NMR. Major
products were then isolated using column chromatography.
Representative Procedures. 10-(Benzyloxy)-10b-hydroxy-1-
phenyl-1H-anthra[1,9-bc]furan-6(10bH)-one (33). A solution of
1352 (75 mg, 0.178 mmol) in 75 mL of benzene was irradiated
using method B for 18 h. Flash column chromatography with
1:1 hexane/EtOAc followed by recrystallization from hexane
gave 33 as a yellow solid (53 mg, 0.126 mmol, 71%): mp
159-161 °C ; IR (KBr) 3447, 3061, 3034, 2925, 1668, 1630,
1591, 1465, 1303, 1287, 1260, 1217, 1018, 888, 757, 733 cm-1; 1H
NMR (300 MHz, CDCl3) δ 7.84-7.79 (m, 3H), 7.56 (d, 1H, J =
7.7 Hz), 7.47-7.36 (m, 4H), 7.27-7.22 (m, 5H), 7.12 (d, 1H, J =
7.9 Hz), 6.97-6.89 (m, 3H), 5.86 (s, 1H), 4.84 (d, 1H, J = 14.0
Hz), 4.68 (d, 1H, J = 14.0 Hz), 2.57 (s, 1H); 13C NMR (75 MHz,
CDCl3) δ 184.0, 158.7, 154.6, 136.3, 136.0, 135.1, 134.1, 131.3,
130.9, 130.7, 130.5, 129.7, 128.8, 128.7, 128.0, 127.8, 126.6,
121.6, 118.2, 118.1, 114.6, 95.1, 73.7, 68.8; HRMS (EI) calcd
for C28H20O4Naþ [M þ Na]þ 443.125380, found 443.125090.
1
1460, 1402, 1352, 1233, 1050, 1004, 780, 702 cm-1; H NMR (300
MHz, CDCl3) δ12.47 (s, 1H), 8.00 (dd, 1H, J= 1.2, 6.7 Hz), 7.90 (dd,
1H, J = 0.6, 7.4 Hz), 7.70 (dt, 1H, J = 1.4, 6.5 Hz), 7.54-7.42 (m,
6H), 7.34 (d, 1H, J=9.2Hz),7.05-6.84 (m, 4H), 6.08 (d, 2H, J=7.1
Hz), 5.77 (s, 1H), 5.24 (s, 2H), 3.58 (d, 1H, J = 12.2 Hz), 3.20 (d, 1H,
J = 12.2 Hz); 13C NMR (75 MHz, CDCl3) δ 188.3, 157.3, 147.9,
145.9, 135.6, 134.9, 134.2, 132.5, 129.9, 129.7, 129.1, 128.8, 127.9, 127.8,
127.4, 126.7, 126.2, 125.7, 121.5, 117.3, 115.6, 74.9, 72.1, 53.6, 36.6;
HRMS (EI) calcd for C28H22O4 Naþ [M þ Na]þ 445.141030, found
445.140743.
Acknowledgment. This work was supported by the NSF
(CHE-0514576). We thank Dr. Marcus Wright and Dr. Cynthia
Day for assistance with NMR spectroscopy and X-ray crystal-
lography, respectively.
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Supporting Information Available: Additional experimental
procedures, 1D and 2D NMR spectra, and X-ray crystallo-
graphic information. This material is available free of charge via
J. Org. Chem. Vol. 75, No. 11, 2010 3813