Selective Oxidation of Vinyl and Silyl Ethers
J . Org. Chem., Vol. 62, No. 21, 1997 7177
13C-NMR (CDCl3, 67.8 MHz) δ 106.0, 71.37, 63.5, 54.6, 31.7,
31.7, 29.3, 25.4, 22.5, 15.3, 14.0.
Ta ble 4. Oxid a tion of Sever a l Cyclic Silyl En ol Eth er s
by th e P CWP -H2O2 System a
1,1-Dieth oxy-2-h yd r oxyocta n e (5): IR (NaCl) 3474, 2927,
1731, 1457, 1375, 1120, 1063, 592 cm-1; 1H-NMR (CDCl3, 270
MHz) δ 4.25 (d, J ) 5.9 Hz, 1 H), 3.81-3.67 (m, J ) 6.9 Hz, 1
H), 3.63-3.52 (m, J ) 6.9 Hz, 4 H), 2.41 (br, 1 H), 1.59-1.20
(m, 16 H), 0.88 (t, J ) 6.9 Hz, 3 H); 13C-NMR (CDCl3, 67.8
MHz) δ 105.4, 72.0, 63.7, 63.3, 32.1, 29.6, 25.8, 22.9, 15.6, 14.3.
1-Eth oxy-1-m eth oxy-2-h yd r oxyh ep ta n e (7): IR (NaCl)
1
3466, 2930, 1066 cm-1; H-NMR (CDCl3, 270 MHz) δ 4.19 (d,
J ) 6.3 Hz, 1 H), 3.83-3.68 (m, J ) 6.9 Hz, 1 H), 3.65-3.53
(m, 2 H), 3.44 (s, 3 H), 3.41 (s, 3 H), 2.17 (br, 1 H), 1.58-1.21
(m, 11 H), 0.89 (t, J ) 6.6 Hz, 3 H); 13C-NMR (CDCl3, 67.5
MHz) δ 106.1, 71.5, 63.9, 63.7, 54.8, 32.0, 31.8, 25.2, 22.7, 15.4,
14.1.
1-Eth oxy-1-m eth oxy-2-h yd r oxyp r op a n e (9): IR (NaCl)
3443, 2977, 1453, 1372, 1065, 628 cm-1; 1H-NMR (CDCl3, 270
MHz) δ 4.15 (d, J ) 6.3 Hz, 1 H), 3.80-3.69 (m, 1 H), 3.66-
3.57 (m, J ) 7.3 Hz, 2 H), 3.43 (d, J ) 7.3 Hz, 3 H) 1.28-1.19
(m, J ) 6.9 Hz, 3 H); 13C-NMR (CDCl3, 67.8 MHz) δ 106.9,
67.7, 63.7, 54.7, 17.4, 15.3.
1-E t h oxy-1-m et h oxy-2-h yd r oxy-3-cycloh exylp r op a n e
(11): IR (NaCl) 3462, 2923, 2850, 1720, 1448, 1285, 1128, 1066
octene (1) were converted into the corresponding R-hy-
droxy acetal 2, preparation of which is difficult by
conventional methods, in a mixed solvent of alcohol and
dichloromethane. The oxidation of acyclic silyl enol
ethers such as 1-[(trimethylsilyl)oxy]-1-octene (15) gave
R-hydroxy ketones such as 1-hydroxy-2-octanone (3) in
satisfactory yields in a mixed solvent of methanol and
dichloromethane. Under phase-transfer conditions using
dichloromethane as the solvent, 15 was converted into a
cleaved product, heptanal 4. This provides a facile
method for preparing aldehydes with one carbon less
than the parent aldehydes.
1
cm-1; H-NMR (CDCl3, 400 MHz) δ 4.16 (d, J ) 6.2 Hz, 1 H),
3.76-3.68 (m, J ) 6.9 Hz, 2 H), 3.63-3.55 (m, J ) 7.0 Hz, 1
H), 3.44 (s, 3 H), 2.15 (s, 1 H), 1.85-0.84 (m, 16 H); 13C-NMR
(CDCl3, 100 MHz) δ 106.4, 69.0, 63.5, 54.8, 39.3, 34.5, 33.7,
32.4, 26.6, 26.4, 26.1, 15.3.
1,1-Dim et h oxy-2-h yd r oxy-2-p h en ylet h a n e (13): IR
(NaCl) 3444, 3063, 3032, 2938, 2833, 1688, 1604, 1495, 1454,
1360, 1191, 1068, 976, 915, 835, 763, 701, 578 cm-1; 1H-NMR
(CDCl3, 270 MHz) δ 7.43-7.26 (m, 5 H), 4.61 (d, J ) 6.6 Hz, 1
H), 4.29 (d, J ) 6.6 Hz, 1 H), 3.46 (s, 3 H), 3.26 (s, 3 H), 2.62
(br, 1 H); 13C-NMR (CDCl3, 67.5 MHz) δ 139.4, 128.2, 127.9,
127.1, 107.6, 74.0, 55.9, 54.9.
P r oced u r e for th e Oxid a tion of 9 to 14.27 To a stirred
solution of 9 (1 mmol) in CHCl3 (5 mL) and H2O (5 mL) were
added RuO2 (0.1 mmol), NaIO4 (6.5 mmol), K2CO3 (0.36 mmol),
and Et3NCH2PhCl (0.01 mmol). The reaction mixture was
stirred at 25 °C for 20 h. 2-Propanol (1 mL) was added to
consume unreacted NaIO4 and RuO4, and the mixture was
filtered through Celite. The organic layer was separated and
washed with H2O. The extract was dried over anhydrous
MgSO4 and evaporated under reduced pressure. The product
was purified by distillation.
Exp er im en ta l Section
Gen er a l P r oced u r es. Enol ethers 1, 6, 10,26 15, 17a , and
19a 25 were synthesized according to the literature procedures
and purified by distillation under reduced pressure or by
column chromatography on silica gel with hexane. 8, 12, and
18a were commercially available and used without further
purification. PCWP was prepared by the method reported
previously.16 GC analysis was performed with a flame ioniza-
tion detector using a 0.2 mm × 25 m capillary column (OV-1).
1H- and 13C-NMR were measured at 270 or 400 MHz and 67.5
or 100 MHz, respectively, in CDCl3 with Me4Si as the internal
standard. Infrared (IR) spectra were measured using NaCl
plate. GC-MS spectra were obtained at an ionization energy
of 70 eV. The product yields were estimated from the peak
areas based on the internal standard technique.
1-Eth oxy-2-m eth oxy-2-pr opan on e (14): 1H-NMR (CDCl3,
270 MHz) δ 4.49 (s, 1 H), 3.62-3.56 (q, J ) 6.9 Hz, 2 H), 3.42
(s, 3 H), 1.26 (t, J ) 6.9 Hz, 3 H); 13C-NMR (CDCl3, 67.5 MHz)
δ 204.1, 103.4, 63.4, 54.6, 24.7, 15.1.
Gen er a l P r oced u r e for t h e Oxid a t ion of Silyl E n ol
Eth er s. To a stirred solution of substrate (1 mmol) and PCWP
(10 mg, 0.5 mol %) in CH2Cl2 (5 mL) was added dropwise 35%
H2O2 (1 mmol) over a period of 1 h under nitrogen atmosphere.
The reaction mixture was stirred at room temperature, and
the workup was performed by the same method as described
above.
Gen er a l P r oced u r e for th e Oxid a tion of Vin yl Eth er s
to r-Hyd r oxy Aceta ls. To a stirred solution of substrate (1
mmol) and PCWP (10 mg, 0.5 mol %) in CH3OH (1 mL) and
CH2Cl2 (4 mL) was added dropwise 35% H2O2 (1 mmol) over a
period of 1 h. The reaction mixture was stirred at 40 °C for
16 h and extracted with dichloromethane. The extract was
dried over anhydrous MgSO4 and evaporated under reduced
pressure. The products were purified by column chromatog-
raphy on silica gel with hexane/ethyl acetate (10-3/1 v/v %).
1-Eth oxy-1-m eth oxy-2-h yd r oxyocta n e (2): IR (NaCl)
Ack n ow led gm en t. This work was financially sup-
ported by Research for the Future program J SPS and
Okishiran Chemical Company Ltd.
Su p p or tin g In for m a tion Ava ila ble: Copies of 13C NMR,
1H NMR, IR spectra for the compounds 2, 5, 7, 9, 11, 13, 14,
17b, 18b, and 19b (29 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
3454, 2927, 1467, 1377, 1279, 1119, 1067 cm-1 1H-NMR
;
(CDCl3, 270 MHz) δ 4.12 (d, J ) 6.2 Hz, 1 H), 3.70 -3.62 (m,
J ) 7.0 Hz, 1 H), 3.56-3.48 (m, J ) 7.0 Hz, 2 H), 3.37 (s, 3H),
2.21 (br, 1 H), 1.19-1.16 (m, 13 H), 0.81 (t, J ) 7.0 Hz, 3 H);
J O970440H
(26) Normant, J . F.; Commercon, A.; Bourgain, M.; Villiras, J .
Tetrahedron Lett. 1975, 3833.
(27) Morris, P. E., J r.; Kiely, D. E. J . Org. Chem. 1987, 52, 1149.