H. Cheng et al. / Tetrahedron 68 (2012) 1171e1176
1175
J¼6.5 Hz, 4H), 2.82e2.77 (m, 4H), 2.77e2.71 (m, 4H), 2.21e1.97 (m,
8H),1.88e1.60 (m, 8H),1.51e1.11 (m, 8H),1.05e0.94 (m, 4H), 0.84 (s,
After being cooled to ambient temperature, the reaction was di-
luted with water (100 mL) and extracted with EtOAc (3ꢂ50 mL).
The combined organic phases were washed with brine, dried
(MgSO4), concentrated in vacuo and purified by flash chromatog-
raphy on silica gel eluting with petroleum ether/ethyl acetate
(80:1) to afford 20 (colorless oil, 110 mg, 0.314 mmol, 25%). IR (KBr)
36H), ꢀ0.01 (s, 18H), ꢀ0.02 (s, 6H); 13C NMR (100 MHz, CDCl3)
d:
134.7, 133.8, 131.4, 130.5, 103.4, 100.2, 79.2, 77.1, 75.8, 74.4, 49.6,
49.2, 48.9, 48.4, 46.2, 45.8, 44.9, 37.9, 36.7, 36.6, 35.7, 35.5, 30.7,
29.0, 28.1, 26.7, 25.9, 25.8, 21.0, 20.8, 18.0, 18.0, ꢀ3.8, ꢀ3.8, ꢀ4.6,
ꢀ4.7; HRMS: m/z 391.2291 [MþNa]þ (calcd for C20H36NaO4Si,
391.2275).
nmax: 2953, 2933, 2858, 1760, 1680, 1582, 1466 cmꢀ1
(400 MHz, CDCl3)
;
1H NMR
d
: 6.17 (d, J¼8.9 Hz, 1H), 5.94 (t, J¼8.1 Hz, 1H),
5.57 (t, J¼7.0 Hz, 1H), 3.28 (s, 3H), 3.22e3.19 (m, 1H), 3.18 (s, 3H),
2.98 (d, J¼6.7 Hz, 1H), 2.54e2.38 (m, 1H), 2.36e2.01 (m, 3H),
1.84e1.52 (m, 2H), 1.27 (dd, J¼12.9, 4.7 Hz, 1H), 0.84 (s, 9H), ꢀ0.00
4.9. Preparation of compounds 17 and 18
Triflic anhydride (636
mL, 3.78 mmol) was slowly added to stir-
(s, 2H). 13C NMR (100 MHz, CDCl3)
d: 133.6, 130.5, 129.9, 123.6,
red solution of 16 (0.69 g, 1.89 mmol) and pyridine (611
m
L,
109.6, 95.3, 76.6, 50.7, 49.7, 45.1, 42.9, 42.5, 39.8, 39.0, 33.6, 25.9,
25.9, 21.3, 18.1, ꢀ4.0, ꢀ4.4; HRMS: m/z 351.2283 [MþH]þ (calcd for
C20H35O3Si, 351.2277).
7.56 mmol) in CH2Cl2 (8 ml) at ꢀ10 ꢁC (acetone/ice) under argon.
Pyridinium triflate salt precipitated and the solution turned brown.
The reaction was complete after 10 h. The reaction mixture was
poured onto ice water (20 mL). The aqueous layer was extracted
with CH2Cl2 (4ꢂ10 mL). The combined organic layers were washed
with brine, dried (MgSO4), concentrated in vacuo and purified by
flash chromatography on silica gel eluting with petroleum ether/
ethyl acetate (60:1) to yield compound 17 (colorless oil, 580 mg,
62.8%) and compound 18 (colorless oil, 132 mg, 20%). Compound 17.
IR (KBr) nmax: 3438, 3075, 2932, 2860, 1749, 1638, 1545, 1456,
4.12. Preparation of compound 21
A solution of 19 (225 mg, 0.615 mmol) in MeOH (5 mL) was
treated with NaBH4 (47 mg, 1.23 mmol) at 0 ꢁC under argon for 3 h.
After evaporation most solution of the reaction mixture, water
(10 mL), and CH2Cl2 (10 mL) was added. The layers were separated
and the aqueous layer was extracted with CH2Cl2 (2ꢂ10 mL). The
combined organic phases were washed with brine, dried (Na2SO4),
concentrated and purified by flash chromatography on silica gel
eluting with petroleum ether/ethyl acetate (16:1) to give crude
colorless oil (180 mg). A solution of the crude oil (180 mg) in THF
(5 mL) was treated with NaH (189 mg, 4.93 mmol) and CH3I
1413 cmꢀ1; 1H NMR (400 MHz, CDCl3)
d
: 6.34 (t, J¼7.4 Hz, 1H), 5.81
(d, J¼8.2 Hz, 1H), 4.50 (s, 1H), 3.26 (s, 6H), 3.01 (td, J¼10.4, 3.8 Hz,
1H), 2.96e2.91 (m, 1H), 2.21e2.10 (m, 1H), 2.01 (d, J¼12.7 Hz, 1H),
1.79 (dd, J¼19.6, 8.2 Hz, 2H), 1.56e1.45 (m, 1H), 1.45e1.31 (m, 1H),
1.31e1.17 (m, 2H), 0.85 (s, 9H), 0.00 (s, 6H); 13C NMR (100 MHz,
CDCl3)
d: 132.0, 131.5, 119.9, 116.8, 102.2, 92.6, 75.8, 49.4, 49.3, 44.6,
(153 m
L, 2.465 mmol) at 50 ꢁC for 30 min. The reaction mixture was
43.1, 36.4, 35.2, 31.2, 27.8, 25.8, 20.6, 18.0, ꢀ3.8, ꢀ4.8; HRMS: m/z
501.1953 [MþH]þ (calcd for C21H36F3O6SSi, 501.1948). Compound
18. IR (KBr) nmax: 3437, 3064, 2934, 2859, 1712, 1664, 1442 cmꢀ1; 1H
diluted with water (10 mL) and EtOAc (5 mL). The layers were
separated and the aqueous layer was extracted with EtOAc
(2ꢂ5 mL). The combined organic extracts were washed with brine,
dried (MgSO4), concentrated in vacuo and purified by flash chro-
matography on silica gel eluting with petroleum ether/ethyl acetate
(20:1) to yield 21 (colorless oil, 172 mg, 0.45 mmol, 73% for two
NMR (400 MHz, CDCl3)
d
: 6.25 (dd, J¼5.9, 3.1 Hz, 1H), 5.71 (dd,
J¼5.9, 3.1 Hz, 1H), 3.84e3.77 (m, 1H), 3.23 (s, 3H), 3.20 (s, 3H), 2.78
(s, 1H), 2.61 (d, J¼17.5 Hz, 1H), 2.52 (d, J¼2.1 Hz, 1H), 2.02 (dd,
J¼41.0, 17.3 Hz, 2H), 1.86e1.65 (m, 2H), 1.55e1.42 (m, 2H), 0.90 (s,
steps). IR (KBr) nmax: 2932, 2857, 1677, 1628, 1457 cmꢀ1
(400 MHz, CDCl3)
;
1H NMR
9H), 0.05 (d, J¼4.8 Hz, 6H); 13C NMR (100 MHz, CDCl3)
d: 137.5,
d
: 5.52 (d, J¼3.1 Hz, 1H), 3.50 (s, 1H), 3.40 (s, 3H),
134.6, 129.4, 129.3, 111.1, 69.9, 50.4, 49.2, 48.9, 41.8, 32.7, 30.2, 29.1,
25.8, 19.4, 18.1, ꢀ4.2, ꢀ4.7; HRMS: m/z 351.2344 [MþH]þ (calcd for
C20H35O3Si, 351.2331).
3.31e3.24 (m, 1H), 3.23 (s, 3H), 3.19 (s, 3H), 2.48 (d, J¼6.1 Hz, 1H),
2.44e2.34 (m, 2H), 2.33e2.26 (m,1H), 2.25e2.19 (m, 1H), 2.02e1.86
(m, 2H), 1.84e1.72 (m, 1H), 1.40e1.26 (m, 1H), 0.86 (s, 9H), 0.01 (s,
6H); 13C NMR (100 MHz, CDCl3)
d: 142.1, 118.8, 107.6, 84.5, 81.3, 57.1,
4.10. Preparation of compound 19
50.7, 47.9, 47.4, 46.5, 38.7, 37.2, 36.7, 33.9, 28.3, 25.8, 25.7, 17.9, ꢀ4.2,
ꢀ4.6. HRMS: m/z 405.2384 [MþNa]þ (calcd for C21H38O4SiNa,
405.2432).
DBU (626 mL, 4.018 mmol) was added to a solution of 17
(520 mg, 1.05 mmol) in DMSO (10 mL) at ambient temperature
under argon. The reaction mixture was rapidly warm to 120 ꢁC and
stirred for 1 h. After cooling to ambient temperature, the reaction
was diluted with water (100 mL) and extracted with EtOAc
(3ꢂ50 mL). The combined organic phases were washed with brine,
dried (MgSO4), concentrated in vacuo and purified by flash chro-
matography on silica gel eluting with petroleum ether/ethyl acetate
(16:1) to afford 19 (colorless oil, 270 mg, 85.2%). IR (KBr) nmax: 2932,
4.13. Preparation of compound 22
To a solution of NaHCO3 (10.7 mg, 0.127 mmol) and mCPBA
(25.5 mg, 85.8%, 0.127 mmol) in CH2Cl2 (2 mL) at 0 ꢁC under argon
a solution of 21 (32 mg, 0.0844 mmol) in CH2Cl2 (0.5 mL) was
added. The resulting mixture was stirred at ambient temperature
for 6 h, and then diluted with satd aq Na2S2O3 (2 mL) and satd aq
Na2HCO3 (10 mL). The layers were separated and the aqueous layer
was extracted with CH2Cl2 (4ꢂ5 mL). The combined organic phases
were washed with brine, dried (Na2SO4), concentrated in vacuo and
purified by flash chromatography on silica gel eluting with petro-
leum ether/ethyl acetate (6:1) to give compound 22 (colorless oil,
2858, 1677, 1627, 1457 cmꢀ1 1H NMR (400 MHz, CDCl3)
; d: 5.91 (s,
1H), 3.26e3.18 (m, 4H), 3.11 (s, 3H), 2.99 (d, J¼7.4 Hz, 1H), 2.85 (d,
J¼6.4 Hz, 1H), 2.66e2.52 (m, 2H), 2.48e2.38 (m, 1H), 2.29e2.20 (m,
1H), 2.11e2.01 (m, 1H), 1.93e1.78 (m, 1H), 1.50e1.35 (m, 1H), 1.15
(dd, J¼13.8, 4.6 Hz, 1H), 0.84 (s, 9H), ꢀ0.02 (d, J¼6.0 Hz, 6H); 13C
NMR (100 MHz, CDCl3)
d
: 201.5, 164.0, 125.0, 110.4, 80.4, 54.1, 51.2,
28 mg, 82%). IR (KBr) nmax: 2933, 2857, 1761, 1724, 1462 cmꢀ1
NMR (400 MHz, CDCl3)
;
1H
49.6, 47.9, 47.1, 37.5, 36.3, 30.5, 27.7, 25.7, 25.7, 17.8, ꢀ4.3, ꢀ4.7;
d
: 3.54 (t, J¼8.5 Hz, 1H), 3.49 (s, 3H), 3.26 (s,
HRMS: m/z 367.2229 [MþH]þ (calcd for C20H35O4Si, 367.2226).
3H), 3.18 (d, J¼3.1 Hz, 1H), 3.14 (s, 3H), 2.47 (d, J¼6.4 Hz, 1H), 2.30
(d, J¼7.4 Hz, 2H), 2.24e2.08 (m, 2H), 1.90e1.76 (m, 1H), 1.76e1.62
(m, 2H),1.56e1.40 (m, 2H), 0.95 (dd, J¼13.2, 4.2 Hz,1H), 0.88 (s, 9H),
4.11. Preparation of compound 20
0.06 (s, 6H); 13C NMR (100 MHz, CDCl3)
d: 181.4, 108.9, 83.3, 78.7,
To a solution of 17 (625 mg, 1.258 mmol) in toluene (10 mL) DBU
(0.75 mL, 5.03 mmol) was added at ambient temperature under
argon. The reaction mixture was warm to 120 ꢁC and stirred for 1 h.
61.4, 57.1, 54.4, 51.1, 46.8, 44.7, 41.8, 40.3, 35.9, 33.9, 33.4, 25.8, 22.0,
17.9, ꢀ4.0, ꢀ4.6; HRMS: m/z 399.2511 [MþH]þ (calcd for
C21H38O5Si, 399.2561).