S. Reim et al. / Tetrahedron Letters 47 (2006) 6903–6905
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9. General procedure for the synthesis of biaryls 6: A
dioxane solution of the boronic acid, potassium phos-
phate, Pd(PPh3)4 and of the triflate 4 was stirred at
110 ꢁC for 4–20 h. After cooling to ambient temperature,
a saturated aqueous solution of NH4Cl was added. The
organic and the aqueous layer were separated and the
latter was extracted with diethyl ether. The combined
organic layers were dried (Na2SO4), filtered and the
filtrate was concentrated in vacuo. The residue was
purified by chromatography. Synthesis of 6a: Starting
with 4-methoxyphenylboronic acid (140 mg, 0.91 mmol),
potassium phosphate (240 mg, 1.12 mmol), Pd(PPh3)4
(24 mg, 0.02 mmol), 5a (230 mg, 0.70 mmol) and dioxane
(1.8 mL), 6a was isolated by chromatography (silica gel,
n-heptane/EtOAc = 9:1) as a colorless oil (158 mg, 79%).
1H NMR (500 MHz, CDCl3): d = 2.23 (s, 3H, CH3),
2.28 (s, 3H, CH3), 2.33 (s, 3H, CH3), 3.61 (s, 3H,
OCH3), 3.83 (s, 3H, OCH3), 6.91 (m, 2H, CH), 7.02 (s,
1H, CH), 7.29 (m, 2H, CH). 13C NMR (125.8 MHz,
CDCl3): d = 15.4, 17.3, 20.7 (CH3), 51.7, 55.2 (OCH3),
113.6, 128.8, 129.3 (CH), 131.7, 133.1, 133.5, 134.2,
136.5, 137.7, 158.8 (C), 171.1 (C@O). IR (neat, cmꢀ1):
70 eV): m/z (%) = 285 (18), 284 (M+, 100), 253 (69), 252
(26), 238 (27). HRMS (EI): calcd for C18H20O3 (M+):
284.14070, found: 284.13999.
10. General procedure for the synthesis of fluorenones 7:
Compound 6 was dissolved in concentrated H2SO4. After
stirring for 1 h, the solution was poured into ice water and
extracted (3·) with diethyl ether. The combined organic
layers were dried (Na2SO4), filtered and the filtrate was
concentrated in vacuo to give 7 as a yellow solid. Synthesis
of 7a: Starting with 6a (96 mg, 0.34 mmol) in H2SO4
(4 mL), 7a was isolated as a yellow solid (73 mg, 85%),
1
mp = 135–136 ꢁC. H NMR (500 MHz, CDCl3): d = 2.13
(s, 3H, CH3), 2.29 (s, 3H, CH3), 2.57 (s, 3H, CH3), 3.83 (s,
3
4
3H, OCH3), 6.91 (dd, 1H, J = 8.2 Hz, J = 2.5 Hz, CH),
4
7.03 (s, 1H, CH), 7.12 (d, 1H, J = 2.5 Hz, CH), 7.29 (d,
1H, 3J = 8.2 Hz, CH). 13C NMR (125.8 MHz, CDCl3):
d = 13.8, 14.6, 15.4 (CH3), 55.7 (OCH3), 108.9, 119.1,
119.7, 120.4 (CH), 129.3, 135.9, 136.3, 136.6, 138.7, 142.7,
143.2, 160.5 (C), 195.2 (C@O). IR (KBr, cmꢀ1): v ¼ 3437
~
(br, m), 2952 (w), 2937 (w), 2833 (w), 1696 (s), 1601 (s),
1482 (m), 1462 (s), 1433 (s), 1372 (w), 1289 (s), 1259 (m),
1222 (s), 1200 (w), 1192 (w), 1069 (w), 1031 (w). MS (EI,
70 eV): m/z (%) = 253 (18), 252 (M+, 100), 237 (67), 165
(48). HRMS (EI): calcd for C17H16O2 (M+): 252.1145,
found: 252.1143. Anal. Calcd for C17H16O2 (252.31): C,
80.93; H, 6.39. Found: C, 80.90; H, 6.51.
~
m ¼ 3031 (w), 2997 (m), 2948 (m), 2865 (w), 2837 (m),
1725 (br s), 1610 (m), 1578 (w), 1516 (s), 1462 (s), 1435
(s), 1394 (m), 1321 (w), 1290 (s), 1260 (s), 1248 (s), 1180
(s), 1164 (s), 1129 (m), 1080 (w), 1043 (s). MS (EI,