Y. Liu et al. / Tetrahedron 60 (2004) 4867–4873
4871
1
acetate, 9:1 v/v) to afford the corresponding benzoins and/or
benzils.
(2c). White solid; mp 111–113 8C; H NMR (400 MHz,
CDCl3) d 7.90–7.94 (m, 2H), 7.25–7.28 (m, 2H), 6.85–
6.90 (m, 4H), 5.87 (d, 1H, J¼5.2 Hz), 4.60 (d, 1H,
J¼5.2 Hz), 3.84 (s, 3H), 3.78 (s, 3H); 13C NMR d
(CDCl3): 197.3, 164.0, 159.6, 132.4, 131.9, 131.6, 129.0,
114.5, 113.9, 75.3, 55.5, 55.2; IR (KBr) 3465, 3077, 2939,
1667, 1598, 1514, 1469 cm21; mass spectrum, m/z
(relative intensity, %) 272 (0.61, Mþ), 255 (0.88,
Mþ2OH), 137 (100), 135 (86.2), 107 (17.31), 77 (80.38).
Anal. Calcd for C16H16O4: C, 70.58; H, 5.92. Found: C,
70.89; H, 5.88.
3.3. Sm/DMF/I2 system promoted rearrangement
reaction of diarylketones with DMF
General procedure. To a mixture of Sm powder (2 mmol)
and diarylketone (2 mmol) in freshly distilled N,N-
dimethylformamide (DMF, 10 mL) I2 (0.13 g, 0.5 mmol)
was added at room temperature, with magnetic stirring
under a nitrogen atmosphere. The reaction mixture was then
heated to a certain temperature so as to ensure that the
reaction occurred (as indicated in Table 2). After the
completion of the reaction (monitored by TLC), dilute
hydrochloric acid (2 M, 5 mL) was added and the resulting
mixture was extracted with diethyl ether (3£20 mL). The
combined organic layer was washed with brine, dried over
anhydrous sodium sulfate, and concentrated under reduced
pressure. The crude products were purified with flash
chromatography (silica/hexanes–ethyl acetate, 9:1 v/v) to
afford the corresponding benzoins and/or benzils.
3.4.4. 1,2-Bis-(4-dimethylamino-phenyl)-2-hydroxy-
ethanone (2d). White solid; mp 153–156 8C; 1H NMR
(400 MHz, CDCl3) d 7.85–7.88 (m, 2H), 7.20–7.22 (m,
2H), 6.66–6.68 (m, 4H), 5.80 (d, 1H, J¼6.0 Hz), 4.68 (d,
1H, J¼6.0 Hz), 2.92 (s, 6H), 3.03 (s, 6H); 13C NMR d
(CDCl3): 196.6, 154.2, 153.6, 132.2, 131.5, 128.6, 110.8,
110.6, 74.9, 40.1, 39.9; IR (KBr) 3420, 2916, 1681, 1595,
1546, 1483 cm21; mass spectrum, m/z (relative intensity, %)
298 (0.24, Mþ), 150 (2.16), 148 (100), 120 (5.51). Anal.
Calcd for C18H22N2O2: C, 72.46; H, 7.43; N, 9.39. Found:
C, 72.54; H, 7.50; N, 9.45.
3.4. SmI2/THF system promoted rearrangement
reaction of diarylketones with DMF
3.4.5. 2-Hydroxy-2-phenyl-1-p-tolyl-ethanone (2f). The
title compound was obtained as a mixture with 3f; white
solid; H NMR (400 MHz, CDCl3) d 7.83–7.85 (m, 2H),
7.14–7.35 (m, 7H), 5.94 (d, 1H, J¼6.0 Hz), 4.61 (d, 1H,
J¼6.0 Hz), 2.38 (s, 3H); IR (KBr) 3441, 3059, 2945, 1675,
1607, 1510, 1491, 1452, 1390 cm21; mass spectrum, m/z
(relative intensity, %) 227 (0.28, Mþþ1), 226 (0.72, Mþ),
209 (2.59, Mþ2OH), 119 (100), 107 (10.37), 91 (55.09), 77
(57.75). Anal. Calcd for C15H14O2: C, 79.62; H, 6.24.
Found: C, 79.48; H, 6.28.
General procedure. To a solution of SmI2 (3 mmol) in THF
(20 mL), diarylketone (1 mmol) was added at room
temperature under a nitrogen atmosphere. The deep blue
color of the solution turned red immediately, and DMF
(0.5 mL) was added. The color of resultant solution
vanished immediately, which indicated that the reaction
had completed. After being stirred for 5–10 min, dilute
hydrochloric acid (2 M, 5 mL) was added and the resulting
mixture was extracted with diethyl ether (3£20 mL). The
combined organic layer was washed with brine, dried over
anhydrous sodium sulfate, and concentrated under reduced
pressure. The crude products were purified with flash
chromatography (silica/hexanes–ethyl acetate, 9:1 v/v) to
afford the corresponding benzoins and/or benzils.
1
3.4.6. 2-Hydroxy-1-phenyl-2-p-tolyl-ethanone (3f). The
title compound was obtained as a mixture with 2f; white
1
solid; H NMR (400 MHz, CDCl3) d 7.93–7.95 (m, 2H),
7.15–7.37 (m, 7H), 5.94 (d, 1H, J¼6.0 Hz), 4.52 (d, 1H,
J¼6.0 Hz), 2.31 (s, 3H); IR (KBr) 3441, 3059, 2945, 1675,
1607, 1510, 1491, 1452, 1390 cm21; mass spectrum, m/z
(relative intensity, %) 227 (0.28, Mþþ1), 226 (0.72, Mþ),
209 (2.59, Mþ2OH), 121 (82.30), 105 (24.30), 91 (55.09),
77 (57.75). Anal. Calcd for C15H14O2: C, 79.62; H, 6.24.
Found: C, 79.48; H, 6.28.
3.4.1. 2-Hydroxy-1,2-diphenyl-ethanone (2a). White
solid, mp 134–136 8C; 1H NMR (400 MHz, CDCl3) d
7.92–7.95 (m, 2H), 7.52–7.54 (m, 1H), 7.40–7.44 (m, 2H),
7.28–7.36 (m, 5H), 5.97 (d, 1H, J¼6.0 Hz), 4.56 (d, 1H,
J¼6.0 Hz); IR (KBr) 3417, 3060, 2933, 1680, 1596, 1491,
1450 cm21; mass spectrum, m/z (relative intensity, %) 213
(1.16, Mþþ1), 212 (0.43, Mþ), 195 (13.95, Mþ2OH), 107
(61.01), 105 (100), 77 (89.62). Anal. Calcd for C14H12O2: C,
79.23; H, 5.70. Found: C, 79.48; H, 5.74.
3.4.7. 1-Biphenyl-4-yl-2-hydroxy-2-phenyl-ethanone
(2g). The title compound was obtained as a mixture with
1
3g; white solid; H NMR (400 MHz, CDCl3) d 8.01–8.03
(m, 2H), 7.29–7.65 (m, 12H), 6.00 (d, 1H, J¼6.0 Hz), 4.60
(d, 1H, J¼6.0 Hz); IR (KBr) 3422, 3031, 1678, 1603, 1560,
1487, 1450, 1407 cm21; mass spectrum, m/z (relative
intensity, %) 181 (38.10), 153 (19.85), 107 (6.91), 77
(100). Anal. Calcd for C20H16O2: C, 83.31; H, 5.59. Found:
C, 83.10; H, 5.56.
3.4.2. 2-Hydroxy-1,2-di-p-tolyl-ethanone (2b). White
1
solid, mp 86–88 8C; H NMR (400 MHz, CDCl3) d 7.83–
7.85 (m, 2H), 7.19–7.24 (m, 4H), 7.13–7.15 (m, 2H), 5.91
(d, 1H, J¼6.0 Hz), 4.55 (d, 2H, J¼6.0 Hz), 2.37 (s, 3H),
2.31 (s, 3H); 13C NMR d (CDCl3): 198.6, 144.9, 138.3,
136.4, 131.0, 129.8, 129.4, 129.3, 127.7, 75.8, 21.7, 21.2; IR
(KBr) 3473, 3038, 2921, 1676, 1607, 1513 cm21; mass
spectrum, m/z (relative intensity, %) 241 (0.36, Mþþ1), 240
(1.20, Mþ), 223 (1.79, Mþ2OH), 121 (85.90), 119 (95.45,
Mþ), 91 (100). Anal. Calcd for C16H16O2: C, 79.97; H, 6.71.
Found: C, 79.68; H, 6.73.
3.4.8. 2-Biphenyl-4-yl-2-hydroxy-1-phenyl-ethanone
(3g). The title compound was obtained as a mixture with
1
2g; white solid; H NMR (400 MHz, CDCl3) d 7.97–8.00
(m, 2H), 7.29–7.65 (m, 12H), 6.02 (d, 1H, J¼6.0 Hz), 4.59
(d, 1H, J¼6.0 Hz); IR (KBr) 3422, 3031, 1678, 1603, 1560,
1487, 1450, 1407 cm21; mass spectrum, m/z (relative
intensity, %) 183 (32.29), 153 (19.85), 105 (28.57), 77
3.4.3. 2-Hydroxy-1,2-bis-(4-methoxyphenyl)-ethanone