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Reaction of Tetrahydropyranyl Ethers with Triethylsilyl Trifluoromethanesulfonate
temperature. The reaction mixture was quenched with phos-
phate buffer (pH 7), and extracted with CH2Cl2. The organic
layer was washed with brine, dried over Na2SO4, filtered,
and evaporated under vacuum. The residue was purified by
flash SiO2 column chromatography using hexanes-AcOEt
(100/1) to give 6 (yield: 9.8 mg, 23%). Colorless oil; IR
(0.55 mL, 4.14 mmol), and 10a (0.19 mL, 2.76 mmol); yield:
355 mg (80%). Eluent: hexanes-AcOEt (20/1). Colorless
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oil; IR (KBr): n=2875, 1099, 748 cmÀ1; H NMR (300 MHz,
CDCl3): d=0.57 (6H, q, J=7.9 Hz), 0.93 (9H, t, J=7.9 Hz),
1.34–1.44 (2H, m), 1.49–1.70 (7H, m), 3.58 (2H, t, J=
6.4 Hz), 3.88–4.10 (4H, m), 4.56 (1H, t, J=5.7 Hz), 5.14
(1H, d, J=9.6 Hz), 5.26 (1H, dd, J=17.1, 1.2 Hz), 5.51–5.76
(2H, m), 5.83–5.96 (1H, m); 13C NMR (75 MHz, CDCl3):
d=4.3, 6.7, 17.7, 21.1, 32.6, 33.2, 62.6, 66.0, 66.1, 101.9,
116.5, 127.4, 129.2, 134.8; anal. calcd. for C18H36O3Si: C
65.80, H 11.04; found: C 65.79, H 10.93.
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(KBr): n=1097 cmÀ1; H NMR (300 MHz, CDCl3): d=0.57
(12H, q, J=8.0 Hz), 0.97 (18H, t, J=8.0 Hz), 1.22–1.38
(16H, m), 1.45–1.58 (4H, m), 3.59 (4H, t, J=6.7 Hz);
13C NMR (75 MHz, CDCl3): d=4.4, 6.8, 25.8, 29.5, 29.59,
29.63, 32.9, 63.0; anal. calcd. for C24H54O2Si2: C 66.90, H
12.63; found: C 67.18, H 12.49.
Mixed acetal 11b: Obtained from 9b[13] (323 mg,
1.90 mmol), TESOTf (0.86 mL, 3.80 mmol), 2,4,6-collidine
(0.75 mL, 5.70 mmol), and 10a (0.26 mL, 3.80 mmol); yield:
516 mg (79%). Eluent: hexanes-AcOEt (25/1). Colorless
Experiment in Scheme 6
oil; IR (KBr): n=912, 742 cmÀ1
;
1H NMR (300 MHz,
According to the general procedure, treatment of
(36.6 mg, 0.059 mmol) with 2,4,6-collidine (23 mL,
0.177 mmol) and TESOTf (27 mL, 0.118 mmol) gave
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CDCl3): d=0.59 (6H, q, J=7.9 Hz), 0.85–0.98 (12H, m),
1.38–1.69 (8H, m), 3.57–3.62 (2H, m), 3.81–4.13 (3H, m),
4.55–4.62 (1H, m), 5.11–5.32 (4H, m), 5.56–5.97 (2H, m);
13C NMR (75 MHz, CDCl3): d=4.4, 6.8, 9.5, 9.8, 21.0, 21.1,
28.1, 28.5, 32.6, 33.7, 62.7, 64.7, 66.2, 79.0, 79.3, 99.9, 101.7,
115.9, 116.3, 116.5, 117.2, 134.9, 135.1, 138.8, 139.4; anal.
calcd. for C19H38O3Si: C 66.61, H 11.18; found: C 66.72, H
11.06.
8
(yield: 22.4 mg, 71%) after purification by flash SiO2
column chromatography using hexanes-AcOEt (10/1). Col-
orless oil; [a]2D0: À12.6 (c 1.40, CHCl3); IR (KBr): n=3482,
1
1612, 1514, 1463 cmÀ1; H NMR (300 MHz, CDCl3): d=0.11
(3H, s), 0.14 (3H, s), 0.62 (6H, q, J=7.2 Hz), 0.91 (9H, s),
0.93 (9H, t, J=7.2 Hz), 1.62-1.77 (3H, m), 1.98 (1H, dd, J=
14.7, 9.0 Hz), 2.07–2.13 (2H, m), 3.35–3.46 (2H, m), 3.80
(3H, s), 3.84 (1H, dd, J=10.8, 4.2 Hz), 4.11–4.18 (2H, m),
4.50 (2H, s), 5.62–5.64 (2H, m), 6.86 (2H, d, J=8.7 Hz),
7.26 (2H, d, J=8.7 Hz); 13C NMR (75 MHz, CDCl3): d=
À4.6, À4.4, 6.6, 6.8, 7.0, 7.1, 18.0, 24.5, 25.7, 25.8, 28.8, 41.8,
55.1, 66.0, 72.7, 74.5, 77.7, 113.5, 127.7, 129.1, 130.6, 133.0,
158.9; HR-MS (FAB): m/z=559.3265, calcd. for
C29H52O5Si2Na (M+ +Na): 559.3251.
Mixed acetal 11c: Obtained from 9c[13] (149 mg,
1.05 mmol), TESOTf (0.47 mL, 2.10 mmol), 2,4,6-collidine
(0.42 mL, 3.15 mmol), and 10b (0.27 mL, 3.15 mmol); yield:
290 mg (84%). Eluent: hexanes-AcOEt (30/1). Colorless
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oil; IR (KBr): n=2875, 1004, 746 cmÀ1; H NMR (300 MHz,
CDCl3): d=0.59 (6H, q, J=7.9 Hz), 0.96 (9H, t, J=7.9 Hz),
1.26–1.45 (2H, m), 1.51–1.68 (4H, m), 2.33 (2H, qt, J=6.6,
1.2 Hz), 3.46-3.54 (1H, m), 3.58–3.66 (3H, m), 3.96–4.14
(2H, m), 4.55 (1H, t, J=5.7 Hz), 5.02–5.19 (3H, m), 5.28
(1H, dq, J=17.1, 1.7 Hz), 5.76–5.98 (2H, m); 13C NMR
(75 MHz, CDCl3): d=4.4, 6.8, 21.1, 32.6, 33.1, 34.3, 62.7,
64.5, 66.3, 102.5, 116.4, 116.6, 134.8, 135.3; anal. calcd. for
C18H36O3Si: C 65.80, H 11.04; found: C 66.02, H 10.87.
General Procedure for Preparation of Mixed Acetals
5 and 11a–d
2,4,6-Collidine (3.0 equivs.) and TESOTf (2.0 equivs.) were
added to a solution of a THPether, 1a or 9a–d, in CH2Cl2
(0.1M) at 08C under nitrogen. The mixture was stirred at
the same temperature. After checking for the disappearance
of the THPether on TLC, EtOH (1.5 equivs.) or an alkenol
10a–c (equivalents are shown in Table 4), was added to the
mixture and the resulting mixture was stirred at room tem-
perature. Disappearance of the polar component was ascer-
tained by TLC. The mixture was quenched with water and
extracted with CH2Cl2. The organic layer was dried over
Na2SO4, filtered, and evaporated under vacuum. The residue
was purified by flash SiO2 column chromatography to give a
mixed acetal, 5 or 11a–d.
Mixed acetal 11d: Obtained from 9d[14] (104 mg,
0.67 mmol), TESOTf (0.30 mL, 1.33 mmol), 2,4,6-collidine
(0.26 mL, 2.00 mmol), and 10c (0.17 mL, 2.00 mmol); yield:
203 mg (89%). Eluent: hexanes-AcOEt (30/1). Colorless
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oil; IR (KBr): n=2952, 1099, 744 cmÀ1; H NMR (300 MHz,
CDCl3): d=0.59 (6H, q, J=7.9 Hz), 0.96 (9H, t, J=7.9 Hz),
1.34–1.44 (2H, m), 1.50–1.72 (7H, m), 2.33 (2H, q, J=
6.7 Hz), 3.45–3.65 (4H, m), 3.91 (1H, dd, J=11.5, 6.4 Hz),
4.04 (1H, dd, J=11.4, 5.7 Hz), 4.53 (1H, t, J=5.8 Hz), 5.03–
5.13 (2H, m), 5.52–5.90 (3H, m); 13C NMR (75 MHz,
CDCl3): d=4.4, 6.7, 17.7, 21.1, 32.6, 33.1, 34.3, 62.7, 64.3,
66.3, 102.3, 116.2, 127.5, 129.2, 135.3; anal. calcd. for
C19H38O3Si: C 66.61, H 11.18; found: C 66.69, H 11.07.
Mixed acetal 5: Obtained from 1a (37.3 mg, 0.15 mmol),
TESOTf (70 mL, 0.31 mmol), 2,4,6-collidine (61 mL,
0.46 mmol), and EtOH (14 mL, 0.23 mmol); yield: 51.2 mg
(83%). Eluent: hexanes-AcOEt (30/1). Colorless oil; IR
1
(KBr): n=2856, 912, 744 cmÀ1; H NMR (300 MHz, CDCl3):
General Procedure for Preparation of Cyclic Acetals
12a and b
d=0.59 (6H, q, J=7.9 Hz), 0.88 (3H, t, J=6.6 Hz), 0.96
(9H, t, J=7.9 Hz), 1.17-1.44 (19H, m), 1.51-1.74 (6H, m),
3.37-3.69 (6H, m), 4.47 (1H, t, J=5.7 Hz); 13C NMR
(75 MHz, CDCl3): d=4.4, 6.6, 14.1, 15.3, 21.1, 22.7, 26.2,
29.3, 29.5, 29.56, 29.59, 29.9, 31.9, 32.7, 33.3, 60.9, 62.7, 65.5,
103.0; anal. calcd. for C23H50O3Si: C 68.59, H 12.51; found:
C 68.76, H 12.36.
Grubbsꢁ 2nd generation catalyst (10 mol%) was added to a
solution of mixed acetal 11a, b in CH2Cl2 (0.05M) at room
temperature under argon. The mixture was stirred at the
same temperature. After checking for the disappearance of
the mixed acetal on TLC, the mixture was evaporated under
vacuum. The residue was purified by flash SiO2 column
chromatography to give the cyclic acetal 12a, b.
Mixed acetal 11a: Obtained from 9a[10a] (216 mg,
1.38 mmol), TESOTf (0.62 mL, 2.76 mmol), 2,4,6-collidine
Adv. Synth. Catal. 2007, 349, 636 – 646
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
645