3410
column chromatography on silica gel (hexane:ethyl acetate, 4:1) gave 6: mp 54–56°C. 1H NMR (CDCl3,
200 MHz) δ 2.29 (s, 3H), 2.85 (m, 4H), 3.78 (s, 3H), 6.84 (d, 2H, J=8.7 Hz), 7.03–7.20 (m, 6H). Anal.
calcd for C16H18O: C, 84.91; H, 8.02. Found: C, 84.58; H, 7.84 (compound 7 purified with hexane:ethyl
acetate, 5:1).
General procedure for the manganese(III)-promoted radical reaction: To a solution of the ketoester
or diketone (1.1 mmol) in benzene under nitrogen was added Mn(III)OAc3. A solution of complex 1
(1 mmol) in benzene was added slowly and the solution was stirred at room temperature until all the
complex has been consumed (10–15 h). A solution of Na2SO3 was then added, and the mixture filtered
with Celite and washed well with ether. The organic layer was washed with brine, dried over MgSO4,
and concentrated in vacuo. Purification of the crude product by column chromatography on silica gel
(hexane:ethyl acetate, 4:1) gave 9: 1H NMR (CDCl3, 200 MHz) δ 2.17 (s, 3H), 2.98 (d, 2H, J=8.8 Hz),
3.52 (t, 1H, J=4.4 Hz), 3.57 (s, 3H), 3.65 (s, 3H), 6.69 (d, 2H, J=8.4 Hz), 6.97 (d, 2H, J=8.4 Hz). Anal.
calcd for C13H16O4: C, 66.09; H, 6.83. Found: C, 65.92; H, 6.65. Compound 10 (hexane:ethyl acetate,
4:1): 1H NMR (CDCl3, 300 MHz) δ 1.95 (m, 4H), 2.40 (m, 2H), 3.10 (q, 2H, J=2.4 Hz), 3.72 (s, 3H),
3.78 (s, 3H), 6.79 (d, 2H, J=8.4 Hz), 7.04 (d, 2H, J=8.4 Hz). Anal. calcd for C15H18O4: C, 68.69; H, 6.92.
Found: C, 68.42; H, 6.97. Compound 11 (hexane:ethyl acetate, 5:1): 1H NMR (CDCl3, 200 MHz) δ 1.93
(s, 3H), 3.19 (close s, 4H), 3.65 (s, 3H), 3.76 (s, 3H), 7.07–7.26 (m, 9H). Anal. calcd for C20H22O4: C,
73.60; H, 6.79. Found: C, 73.15; H, 6.46. Compound 12 (hexane:ethyl acetate, 3:1): 1H NMR (CDCl3,
200 MHz) δ 2.10 (s, 6H), 2.60 (d, 2H, J=7.2 Hz), 3.17 (s, 2H), 3.77 (s, 3H), 5.03 (d, 1H, J=15.8 Hz),
5.18 (d, 1H, J=15.8 Hz), 5.54 (m, 1H), 6.79 (d, 2H, J=8.7 Hz), 6.96 (d, 2H, J=8.7 Hz). HRMS calcd. for
C16H20O3 (M+): 259.3310. Found: 259.2754.
Acknowledgements
We are grateful to the National Council of Taiwan for financial support.
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