10.1002/ejoc.201900745
European Journal of Organic Chemistry
FULL PAPER
Dinaphtho[2,1-b:1',2'-d]furan (2l): The product was isolated as a white
solid (27 mg, 49%), mp 102-103 oC. 1H NMR (400 MHz, CDCl3) δ 9.17 (d,
J = 8.5 Hz, 2H), 8.08 (d, J = 8.0 Hz, 2H), 7.97 (d, J = 8.8 Hz, 2H), 7.85 (d,
J = 8.9 Hz, 2H), 7.80 – 7.70 (m, 2H), 7.60 (t, J = 7.2 Hz, 2H) ppm. 13C
NMR (100 MHz, CDCl3) δ 154.5, 131.4, 129.7, 128.8, 128.5, 126.3,
3-(Trifluoromethoxy)-9H-xanthene (4e): The product was isolated as a
o
1
white solid (27 mg, 51%), mp 142-143 C. H NMR (400 MHz, CDCl3) δ
7.20 (dd, J = 20.3, 7.9 Hz, 3H), 7.06 (t, J = 6.8 Hz, 2H), 6.94 (s, 1H), 6.90
(d, J = 8.4 Hz, 1H), 4.04 (s, 2H) ppm. 13C NMR (100 MHz, CDCl3) δ
152.6, 151.5, 148.5, 130.4, 129.8, 129.1, 128.7, 128.0, 123.6, 121.9,
121.1, 120.1, 119.4, 119.3, 116.6, 115.6, 109.7, 27.5 ppm. HRMS (EI)
m/z calcd for C14H9F3O2 [M]+: 266.0549, found: 266.0555.
125.8, 124.6, 119.6, 112.9 ppm. HRMS (APCI) m/z calcd for C20H13
[M+H]+: 269.0961, found: 269.0961.
O
2,4,7-Trimethyldibenzo[b,d]furan (2m): The product was isolated as a
white solid (32 mg, 76%), mp 71-72 oC. 1H NMR (400 MHz, CDCl3) δ
7.77 (d, J = 7.8 Hz, 1H), 7.53 (s, 1H), 7.37 (s, 1H), 7.13 (d, J = 7.8 Hz,
1H), 7.05 (s, 1H), 2.55 (s, 3H), 2.52 (s, 3H), 2.47 (s, 3H) ppm. 13C NMR
(100 MHz, CDCl3) δ 156.9, 153.5, 137.3, 132.1, 128.9, 123.9, 123.8,
122.2, 121.3, 120.3, 117.8, 112.0, 22.1, 21.4, 15.3 ppm. HRMS (ESI) m/z
calcd for C15H15O [M+H]+: 211.1117, found: 211.1120.
3-Chloro-9H-xanthene (4f): The product was isolated as a white solid
(27 mg, 62%), mp 129-130 oC. 1H NMR (400 MHz, CDCl3) δ 7.23 – 7.13
(m, 2H), 7.09 (d, J = 8.1 Hz, 1H), 7.07 – 6.97 (m, 4H), 4.01 (s, 2H) ppm.
13C NMR (100 MHz, CDCl3) δ 152.6, 151.6, 132.8, 129.9, 129.1, 128.0,
123.5, 123.2, 120.2, 119.2, 116.9, 116.7, 27.6 ppm. HRMS (EI) m/z calcd
for C13H9ClO [M]+: 216.0336, found: 216.0340.
3-Methoxy-9H-xanthene (4g): The product was isolated as a white solid
(28 mg, 67%), mp 82-83 oC. 1H NMR (400 MHz, CDCl3) δ 8.33 (d, J = 7.9
Hz, 1H), 8.26 (d, J = 8.9 Hz, 1H), 7.69 (t, J = 7.7 Hz, 1H), 7.46 (d, J = 8.3
Hz, 1H), 7.37 (t, J = 7.2 Hz, 1H), 6.95 (d, J = 8.9 Hz, 1H), 6.89 (s, 1H),
3.94 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3) δ 176.4, 165.2, 158.2,
156.3, 134.4, 128.4, 126.8, 124.0, 122.1, 117.8, 115.9, 113.4, 100.3,
100.1, 56.0 ppm. HRMS (EI) m/z calcd for C14H12O2 [M]+: 212.0832,
found: 212.0836.
8-Methoxy-2,4-dimethyldibenzo[b,d]furan (2n): The product was
isolated as a white solid (38 mg, 83%), mp 82-83 oC. 1H NMR (400 MHz,
CDCl3) δ 7.54 (s, 1H), 7.45 (d, J = 8.9 Hz, 1H), 7.37 (d, J = 2.6 Hz, 1H),
7.07 (s, 1H), 7.02 (dd, J = 8.9, 2.7 Hz, 1H), 3.91 (s, 3H), 2.55 (s, 3H),
2.47 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3) δ 155.8, 154.4, 151.3,
132.0, 129.5, 125.3, 124.0, 121.5, 118.0, 114.9, 112.2, 104.0, 56.2, 21.4,
15.3 ppm. HRMS (ESI) m/z calcd for C15H15O2 [M+H]+: 227.1067, found:
227.1061.
Methyl 2,7-dimethoxy-9H-xanthene-1-carboxylate (4h): The product
was isolated as a white solid (32 mg, 53%), mp 116-117 oC. 1H NMR
(400 MHz, CDCl3) δ 7.05 (d, J = 9.0 Hz, 1H), 6.94 (d, J = 8.9 Hz, 1H),
6.81 (d, J = 9.0 Hz, 1H), 6.75 (dd, J = 8.9, 3.0 Hz, 1H), 6.66 (d, J = 2.9
Hz, 1H), 3.97 (s, 5H), 3.82 (s, 3H), 3.77 (s, 3H) ppm. 13C NMR (100 MHz,
CDCl3) δ 167.9, 155.4, 152.2, 146.2, 145.7, 122.6, 119.9, 119.1, 118.5,
117.1, 113.9, 113.2, 111.2, 56.7, 55.8, 52.6, 26.6 ppm. HRMS (ESI) m/z
calcd for C17H17O5 [M+H]+: 301.1071, found: 301.1072.
Methyl
6,8-dimethyldibenzo[b,d]furan-3-carboxylate (2o): The
product was isolated as a white solid (27 mg, 54%), mp 98-99 oC. 1H
NMR (400 MHz, CDCl3) δ 8.24 (s, 1H), 8.03 (d, J = 8.1 Hz, 1H), 7.92 (d,
J = 8.1 Hz, 1H), 7.60 (s, 1H), 7.15 (s, 1H), 3.97 (s, 3H), 2.57 (s, 3H), 2.48
(s, 3H) ppm. 13C NMR (100 MHz, CDCl3) δ 167.2, 155.9, 154.9, 132.8,
130.9, 129.1, 128.6, 124.0, 122.9, 121.8, 120.3, 118.7, 113.3, 52.4, 21.4,
15.3 ppm. HRMS (ESI) m/z calcd for C16H15O3 [M+H]+: 255.1016, found:
255.1011.
tert-Butyl 9H-xanthene-9-carboxylate (4i): The product was isolated as
a white solid (33 mg, 59%), mp 132-133 oC. 1H NMR (400 MHz, CDCl3) δ
7.33 – 7.22 (m, 4H), 7.16 – 7.11 (m, 2H), 7.08 (td, J = 7.4, 1.2 Hz, 2H),
4.87 (s, 1H), 1.35 (s, 9H) ppm. 13C NMR (100 MHz, CDCl3) δ 171.3,
151.5, 128.9, 123.2, 119.1, 117.0, 81.8, 46.6, 27.9 ppm. 13C NMR (100
MHz, dept135, CDCl3) δ 128.9, 128.8, 123.1, 116.9, 46.4, 27.8 ppm.
HRMS (ESI) m/z calcd for C18H19O3 [M+H]+: 283.1329, found: 283.1330.
9H-Xanthene (4a): The product was isolated as a white solid (31 mg,
85%), mp 101-102 oC. 1H NMR (400 MHz, CDCl3) δ 7.19 (dd, J = 13.7,
7.2 Hz, 4H), 7.09 – 7.04 (m, 4H), 4.06 (s, 2H) ppm. 13C NMR (100 MHz,
CDCl3) δ 152.1, 129.1, 127.8, 123.1, 120.7, 116.6, 28.0 ppm. HRMS (EI)
m/z calcd for C13H10O [M+H]+: 182.0726, found: 182.0730.
3-Fluoro-9H-xanthene (4b): The product was isolated as a white solid
(28 mg, 69%), mp 113-114 oC. 1H NMR (400 MHz, CDCl3) δ 7.19 (dd, J =
18.0, 8.3 Hz, 2H), 7.14 – 7.08 (m, 1H), 7.07 – 7.00 (m, 2H), 6.76 (dd, J =
13.0, 9.0 Hz, 2H), 4.01 (s, 2H) ppm. 13C NMR (100 MHz, CDCl3) δ 163.3,
160.9, 152.7, 152.6, 151.6, 129.8, 129.8, 129.1, 127.9, 123.5, 120.4,
116.6, 116.3, 110.3, 110.0, 104.2, 103.9, 27.4 ppm. HRMS (EI) m/z calcd
for C13H9FO [M+H]+: 200.0632, found: 200.0636.
9-Phenyl-9H-xanthene (4j): The product was isolated as a yellow solid
(42 mg, 82%), mp 136-137 oC. 1H NMR (400 MHz, CDCl3) δ 7.92 – 7.86
(m, 1H), 7.35 – 7.20 (m, 7H), 7.11 – 7.05 (m, 3H), 6.94 (d, J = 7.5 Hz,
2H), 5.85 (s, 1H) ppm. 13C NMR (100 MHz, CDCl3) δ 146.4, 142.8, 140.1,
131.2, 129.9, 128.5, 128.4, 128.2, 128.1, 126.6, 60.9 ppm. 13C NMR (100
MHz, dept135, CDCl3) δ 140.0, 131.0, 129.8, 128.4, 128.3, 128.1, 126.5,
60.8 ppm. HRMS (EI) m/z calcd for C19H14O [M]+: 258.1039, found:
258.1040.
2-Fluoro-9H-xanthene (4c): The product was isolated as a white solid
(21 mg, 53%), mp 117-118 oC. 1H NMR (400 MHz, CDCl3) δ 7.25 – 7.12
(m, 2H), 7.03 (dd, J = 7.8, 4.7 Hz, 2H), 7.01 – 6.96 (m, 1H), 6.90 (dd, J =
14.0, 5.7 Hz, 2H), 4.04 (s, 2H) ppm. 13C NMR (100 MHz, CDCl3) δ 159.7,
157.3, 152.0, 148.2, 128.9, 129.0, 123.3, 122.2, 122.1, 119.7, 117.7,
117.6, 116.6, 115.1, 114.9, 114.6, 114.4, 28.3 ppm. HRMS (EI) m/z calcd
for C13H9FO [M]+: 200.0632, found: 200.0633.
General procedure to synthesize xanthone derivatives (5). To a tube
was added 6-membered CDPIs (0.2 mmol, 1.0 equiv), TEMPO (1.2
equiv), Na2CO3 (3.0 equiv), Cu(OAc)2 (0.1 equiv), 1,2-glycol (3.0 equiv),
5 % H2O/DMF (1.0 mL, 0.2 M). Then the tube was sealed, degassed and
recharged with argon. The reaction proceeded at 100 oC for 12 h under
argon atmosphere. The remained mixture was extracted with EtOAc, the
combined organic layers were washed with H2O and brine and dried over
anhydrous Na2SO4, evaporated in vacuo. The residue was purified by
3-(Trifluoromethyl)-9H-xanthene (4d): The product was isolated as a
o
1
white solid (32 mg, 65%), mp 124-125 C. H NMR (400 MHz, CDCl3) δ
7.30 (s, 1H), 7.25 (d, J = 5.9 Hz, 2H), 7.23 – 7.14 (m, 2H), 7.05 (dd, J =
7.4, 3.7 Hz, 2H), 4.08 (s, 2H) ppm. 13C NMR (100 MHz, CDCl3) δ 152.2,
151.6, 130.5, 130.2, 129.6, 129.0, 128.2, 125.3, 124.7, 123.7, 122.6,
119.8, 119.7, 119.6, 116.7, 114.0, 113.9 ppm. HRMS (APCI) m/z calcd
for C14H8F3O [M-H]-: 249.0533, found: 249.0536.
column chromatography on
a silica gel (PE/EtOAc) to provide
compounds 5.
9H-Xanthen-9-one (5a): The product was isolated as a white solid (28
mg, 71%), mp 171-172 oC. 1H NMR (400 MHz, CDCl3) δ 8.53 (d, J = 7.6
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