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M. M. Meloni et al. / Tetrahedron 63 (2007) 299–311
portionwise [CAUTION: evolution of H2 gas]. After 10 min
benzyl chloride (6.32 g, 0.05 mol) was added and the result-
ing solution was gradually warmed to rt. After 6 h, crushed
ice was added to the mixture followed by extraction with
Et2O (3ꢂ100 mL). The combined organic layers were
washed with water (3ꢂ200 mL), dried (MgSO4) and con-
centrated under reduced pressure to give a yellow liquid.
Purification was achieved by distillation (87–90 ꢀC at
0.02 mmHg) or by chromatography (hexane/EtOAc, 3:1)
to afford 6 (7.10 g, 36.50 mmol, 73%) as a colourless liquid.
1H NMR and bp data were consistent with the literature.31
Rf: 0.43 (hexane/EtOAc, 3:1); FTIR (neat) nmax: 3417 (br,
O–H), 2969 (m), 2934 (m), 1453 (m), 1364 (s), 1152 (s,
C–O), 1095 (s, C–OH), 736 (s); 1H NMR (300 MHz,
CDCl3) d: 7.41–7.20 (m, 5H), 4.50 (s, 2H), 3.69 (t,
J¼6.0 Hz, 2H), 3.44 (br s, 1H), 1.79 (t, J¼6.0 Hz, 2H),
1.23 (s); 13C NMR (75 MHz, CDCl3) d: 137.5 (s), 128.1
(d), 127.4 (d), 127.3 (d), 72.9 (t), 70.0 (s), 67.3 (t), 41.3
(t), 29.0 (q).
for siloxane 8, compound 9 was obtained as a colourless
oil (1.33 g, 3.28 mmol, 90%) by the reaction between silyl
chloride 7 and MeOH. Rf: 0.44 (hexane/CH2Cl2, 1:1);
FTIR (neat) nmax: 3068 (w), 2971 (w), 2937 (w), 1429 (m),
1
1366 (m), 1113 (s), 1078 (s), 1025 (s), 738 (s); H NMR
(300 MHz, CDCl3) d: 7.70–7.50 (m, 4H), 7.45–7.20 (m,
11H), 4.46 (s, 2H), 3.67 (t, J¼7.3 Hz, 2H), 3.51 (s, 3H),
1.89 (t, J¼7.3 Hz, 2H), 1.27 (s, 6H); 13C NMR (75 MHz,
CDCl3) d: 138.5 (s), 134.8 (d), 134.6 (s), 129.8 (d), 128.2
(d), 127.6 (d), 127.5 (d), 127.4 (d), 74.8 (s), 72.9 (t), 67.0
(t), 50.0 (q), 43.9 (t), 30.2 (q); ESMS: m/z: 429 [M+Na]+;
HR ESMS exact mass calculated for C25H30O3SiNa
[M+Na]: 429.1856; found 429.1851.
3.1.5. (2S)-[(3-Benzyloxy-1,1-dimethylpropoxy)di-
methylsilanoxy]propionic acid methyl ester (10). Follow-
ing the general method described for siloxane 8, compound
10 was obtained as a colourless oil (1.62 g, 3.39 mmol, 93%)
by the reaction between silyl chloride 7 and S-(ꢁ)-methyl
lactate (17). Rf: 0.50 (hexane/EtOAc, 5:1); [a]D: ꢁ1.84 (c
5.2, EtOAc); FTIR (neat) nmax: 3068 (w), 3035 (w), 2983
(w), 1748 (s), 1360 (w), 1124 (s), 1062 (s), 854 (s), 850
3.1.2. [3-(Benzyloxy)-1,1-dimethylpropoxy](chloro)-di-
phenylsilane (7). To a rapidly stirred solution of 3ꢀ alcohol
6 (710 mg, 3.65 mmol) in CH2Cl2 (15 mL) at 0 ꢀC, Et3N
(1.52 mL, 10.96 mmol) was added, followed by dichlorodi-
phenylsilane (0.77 mL, 3.66 mmol) and DMAP (447 mg,
3.66 mmol). After the complete disappearance of the start-
ing material by TLC (5 min required, Rf: 0.65, hexane/
EtOAc, 3:1) the chlorosiloxane formed was used in situ for
further transformations.
1
(s), 741 (s); H NMR (300 MHz, CDCl3) d: 7.65 (m, 4H),
7.25–7.50 (m, 11H), 4.46 (s, 2H), 4.44 (q, J¼6.6 Hz, 1H),
3.66 (t, J¼7.3 Hz, 2H), 3.59 (s, 3H), 1.88 (t, J¼7.3 Hz,
2H), 1.37 (d, J¼6.6 Hz, 3H), 1.27 (s, 3H), 1.26 (s, 3H);
13C NMR (75 MHz, CDCl3) d: 174.0 (s), 138.5 (s), 135.1
(d), 134.3 (d), 134.1 (d), 130.0 (d), 128.3 (d), 127.6 (d),
127.5 (s), 75.2 (s), 72.9 (t), 68.2 (d), 67.0 (t), 51.7 (q), 43.8
(t), 30.2 (q), 21.2 (q); 29Si NMR (80 MHz, CDCl3) d:
ꢁ56.4; CIMS m/z: 285 [Ph2Si]O–CH(CH3)(C]O)OMe]+
(50%), 177 [BnOCH2CH2(CH3)2C]+ (36%), 91 [C6H5CH2]+
(100%); HR ESMS exact mass calculated for C28H34O5SiNa
[M+Na]: 501.2068; found 501.2080. Anal. Calcd for
C28H34O5Si: C, 70.26 H, 7.16; found: C 70.30, H 7.07.
3.1.3. General method for the formation of siloxanes 8–
12: [3-(benzyloxy)-1,1-dimethylpropoxy]diphenyl-{[(E)-
3-phenyl-2-propenyl]oxy}silane (8). To a rapidly stirred
solution of 7 (3.65 mmol, theoretical) in CH2Cl2 (15 mL)
prepared using the above procedure, further Et3N (1.52 mL,
10.96 mmol) was added followed by trans-cinnamyl alcohol
(15, 490 mg, 3.66 mmol) and DMAP (446 mg, 3.65 mmol)
under N2. After 20 min, the reaction mixture was partitioned
between water (100 mL) and Et2O (150 mL). The organic
phase was then washed with 10% aqueous KHSO4 (2ꢂ
100 mL), saturated Na2CO3 (2ꢂ100 mL) and brine
(100 mL). Evaporation of the solvent under reduced pressure
and chromatography on silica afforded siloxane 8 as a clear
oil (1.80 g, 3.57 mmol, 98%). Rf: 0.76 (hexane/EtOAc,
3:1); FTIR (neat) nmax: 3049 (w), 2978 (w), 1943 (w), 1450
(w), 1427 (w), 1365 (w), 1110 (s), 1058 (s), 963 (s), 736
3.1.6. (1R,2S,5R)-(3-Benzyloxy-1,1-dimethylpropoxy)-(2-
isopropyl-4-methylcyclohexyloxy)diphenylsilane (11).
Following the general method described for siloxane 8,
compound 11 was obtained as a colourless oil (1.74 g,
3.28 mmol, 90%) by the reaction between silyl chloride 7
and (1R,2S,5R)-(ꢁ)-menthol (18). Rf: 0.57 (hexane/
CH2Cl2, 1:1); [a]D: ꢁ0.25 (c 1, EtOAc); FTIR (neat) nmax
:
3067 (w), 2953 (w), 2921 (w), 1156 (m), 1111 (s), 1049
(s), 740 (s); H NMR (300 MHz, CDCl3) d: 7.70–7.60 (m,
1
4H), 7.45–7.25 (m, 11H), 4.46 (s, 2H), 3.68 (t, J¼7.0 Hz,
2H), 3.49 (td, J¼10.0, 4.0 Hz, 1H), 2.32 (m, 1H), 1.95 (m,
1H), 1.86 (t, J¼7.0 Hz, 2H), 1.47–1.60 (m, 2H), 1.35–1.00
(m, 9H), 0.86 (d, J¼7.3 Hz, 3H), 0.81 (d, J¼6.0 Hz, 3H,
overlapped with 2H, m), 0.49 (d, J¼6.0 Hz, 3H); 13C
NMR (75 MHz, CDCl3) d: 138.6 (s), 136.0 (s), 135.5 (d),
135.1 (d), 129.6 (d), 128.3 (d), 127.6 (d), 127.4 (d), 74.7
(s), 73.5 (d), 72.9 (t), 67.2 (t), 50.2 (d), 45.4 (t), 43.9 (t),
34.4 (t), 31.5 (d), 30.3 (q), 25.2 (d), 22.6 (t), 22.3 (q),
21.3 (q), 15.6 (q); 29Si NMR (80 MHz, CDCl3) d: ꢁ49.3;
EIMS m/z: 395 [(CH3)2C]OSiPh2OMenthyl]+ (8%), 337
[Ph2Si]OMenthyl]+ (10%), 199 [Ph2Si]OH]+ (89%), 91
[C6H5CH2]+ (100%); HR ESMS exact mass calculated for
C34H46O3SiNa [M+Na]: 553.3108; found: 553.3104.
1
(s,), 712 (s); H NMR (300 MHz, CDCl3) d: 7.90–7.70 (dt,
J¼5.8, 1.4 Hz, 4H), 7.40–7.10 (m, 16H), 6.54 (dt, J¼15.4,
1.5 Hz, 1H), 6.20 (dt, J¼15.4, 5.1 Hz, 1H), 4.40 (s, 2H),
4.34 (dd, J¼5.1, 1.5 Hz, 2H), 3.62 (t, J¼7.2 Hz, 2H), 1.86
(t, J¼7.2 Hz, 2H), 1.24 (s, 6H); 13C NMR (75 MHz,
CDCl3) d: 138.5 (s), 137.0 (s), 135.0 (s), 134.7 (d), 130.0
(d), 129.9 (d), 128.5 (d), 128.4 (d), 128.3 (d), 127.7 (d),
127.6 (d), 127.5 (d), 127.4 (d), 126.4 (d), 75.0 (s), 73.3 (t),
67.1 (t), 63.6 (t), 44.0 (t), 30.7 (q, CH3); 29Si NMR
(80 MHz, CDCl3) d: –45.9; CIMS m/z: 315 [Ph2Si]
OCH2CH]CHPh]+ (2%), 177 [BnOCH2CH2(CH3)2C]+
(36%), 117 [PhCH]CH–CH2]+ (28%), 91 [C6H5CH2]+
(100%). Anal. Calcd for C33H36O3Si: C 77.91, H 7.13; found:
C 77.72, H 7.16.
3.1.7. (1S,2R)-(3-Benzyloxy-1,1-dimethylpropoxy)-di-
phenyl-(1,1,7-trimethylbicyclo[2.2.1]hept-2-yloxy)silane
(12). Following the general method described for siloxane 8,
3.1.4. (3-Benzyloxy-1,1-dimethylpropoxy)methoxydi-
phenylsilane (9). Following the general method described