1823w, 1753s, 1590m, 1494m, 1454s, 1429s, 1371s, 1263s, 1177s
br, 1119s br, 1072s, 1028s, 882s, 838s, 816s, 729s, 699s; δH (200
MHz, CDCl3) 1.14 (3 H, t, J 7.1, CH2CH3), 1.37 (3 H, s, CH3),
1.62 (3 H, s, CH3), 2.12 (2 H, apparent d, apparent J 8.2,
(3S,4R,5R)-2-Oxa-1,1-diphenyl-3-methyl-5-(propen-2-yl)-
silinan-4-ol (16) and (3S,4S,5R)-2-oxa-1,1-diphenyl-3-methyl-5-
(propen-2-yl)silinan-4-ol (18)
To a stirred solution of aldehyde 14 (228 mg, 0.70 mmol) in
anhydrous dichloromethane (7 mL) at room temperature was
added dimethylaluminium chloride (1.0 M in hexanes, 634 µL,
0.63 mmol). After 20 min the reaction was quenched by the
addition of saturated aqueous Na2SO4 solution (5 mL) and the
mixture partitioned between water (20 mL) and ether (20 mL).
The aqueous layer was extracted with ether (3 × 10 mL); the
combined organic layers washed with saturated aqueous
NaCl solution (40 mL), dried (Na2SO4) and solvents removed
in vacuo. The resulting oil was purified by flash column chrom-
atography (30 : 1, petrol : ether) to furnish the major product (16)
as colourless needles (109 mg, 48%) and a minor product (18) as
a colourless syrup (11 mg, 5%). Data for 16: Rf 0.38 (2 : 1, petrol
: ether); mp 82–85 ЊC (from ether); [α]2D2 Ϫ25.0 (c 0.62 in CHCl3);
νmax (KBr)/cmϪ1 3521m, 3071m, 2970m, 2878m, 1635w, 1590w,
1489w, 1430s, 1371m, 1334w, 1307w, 1264w, 1180w, 1157m,
1120s, 1072s, 1037m, 1018s, 997m, 978s, 941w, 910m, 892w,
824w, 804m, 772m, 743s, 712s, 701s; δH (400 MHz, CDCl3)
1.32–1.36 (2 H, m, SiCH2), 1.47 (3 H, d, J 6.0, CHCH3), 1.80
SiCH ), 3.90–4.10 (2 H, m, OCH ), 5.20 (1 H, br t, J 8.2, CH᎐
᎐
2
2
C), 5.28 (1 H, s, PhCH ), 7.33–7.70 (15 H, m, Ph); δC (50 MHz,
CDCl3) 14.0, 16.2, 17.6, 25.8, 61.0, 74.7, 117.1, 126.6, 127.8,
128.2, 128.8, 130.0, 131.5, 134.1, 135.0, 138.8, 171.7; m/z
ϩ
(CIϩ) 448 (MNH4 , 5%), 361 (100), 333 (12), 244 (9), 216 (10),
167 (14).
(S )-2-[(3-Methylbut-2-enyl)diphenylsilanyloxy]propionaldehyde
(14)
To a stirred solution of ester 12 (530 mg, 1.44 mmol) in
anhydrous dichloromethane (15 mL) cooled to Ϫ78 ЊC was
added di(isobutyl)aluminium hydride (1.0 M in dichloro-
methane, 2.16 mL, 2.16 mmol) dropwise and the solution
stirred at Ϫ78 ЊC for 45 min. The reaction was quenched by the
addition of a saturated solution of tartaric acid in methanol
(2 mL). The mixture was warmed to room temperature and
partitioned between aqueous tartaric acid solution (30% w/v,
20 mL) and ether (25 mL). The aqueous layer was extracted
with ether (2 × 25 mL) and the combined organic extracts
washed with saturated aqueous NaCl solution (40 mL), dried
(MgSO4) and solvents removed in vacuo. The crude product
was purified by flash column chromatography (30 : 1, petrol :
ether) to furnish aldehyde 14 as a colourless oil (285 mg, 61%).
Rf 0.26 (10 : 1, petrol : ether, [streaks]); [α]2D2 Ϫ14.7 (c 1.10,
CHCl3); νmax (film)/cmϪ1 3070m, 3050m, 3024m, 2975m, 2913m,
2856m, 2803w, 1960w, 1889w, 1822w, 1739s, 1590w, 1429s,
1376m, 1160m, 1118s, 1011m, 998m, 967w, 859w, 816m, 734s,
701s; δH (400 MHz, CDCl3) 1.29 (3 H, d, J 6.8, OCHCH3),
(3 H, br s, C(CH )᎐), 2.51 (1 H, td, J 10.0, 6.8, SiCH CH ), 3.25
᎐
3
2
(1 H, dd, J 10.0, 8.4, CH(OH)), 3.88 (1 H, qd, J 8.4, 6.0,
CHCH ), 4.88 and 4.94 (2 × 1 H, 2 × br s, C(CH )᎐CH ), 7.33–
᎐
3
3
2
7.50 (6 H, m, Ph), 7.54–7.57 (2 H, m, Ph), 7.67–7.71 (2 H, m,
Ph); δC (100 MHz, CDCl3) 15.0, 17.7, 21.8, 49.8, 74.4, 74.5,
113.8, 127.9, 128.2, 130.1, 130.3, 133.9, 134.3, 134.8, 147.5; m/z
ϩ
(CIϩ) 342 (MNH4 , 16%), 325 (MHϩ, 45), 307 (21), 281 (20),
255 (75), 247 (95), 233 (26), 216 (57), 203 (100), 181 (14), 156
(24), 138 (14), 109 (24); Accurate mass (CIϩ): Found 342.1879,
ϩ
C20H28NO2Si (MNH4 ) requires 342.1889. Data for 18: Rf
1.43 and 1.66 (2 × 3 H, 2 × d, J 1.2, ᎐C(CH ) ), 2.12 (2 H,
0.33 (2 : 1, petrol : ether); [α]2D2 Ϫ44.4 (c 0.50, CHCl3); νmax (film)/
cmϪ1 3455s, 3069m, 2973m, 2930m, 1643m, 1428s, 1375w,
1261w, 1118s, 1070m, 997m, 957m, 914w, 852w, 821w, 782m,
737s, 699s; δH (400 MHz, CDCl3) 1.11 (1 H, dd, J 14.4, 3.2,
SiCHHeq), 1.43 (3 H, d, J 6.8, CHCH3), 1.49 (1 H, t, J 14.4,
᎐
3
2
br apparent d, apparent J 8.0, SiCH2), 4.19 (1 H, qd, J 6.8,
1.2, OCHCH ), 5.23 (1 H, tsept, J 8.0, 1.2, CH᎐C(CH ) ), 7.38–
᎐
3
3 2
7.48 (6 H, m, Ph), 7.61–7.68 (4 H, m, Ph), 9.46 (1 H, d,
J 1.2, CHO); δC (100 MHz, CDCl3) 16.1, 17.6, 18.4, 25.7, 74.3,
116.9, 127.9, 128.0, 130.0, 130.2, 130.4, 131.7, 134.2, 134.3,
SiCH H), 1.70 (1 H, br s, CH(OH )), 1.84 (3 H, br s, C(CH )᎐),
᎐
3
ax
ϩ
134.7, 134.8, 135.4, 203.5; m/z (CIϩ) 342 (MNH4 , 39%),
2.46 (1 H, br d, J 14.4, SiCH2CH ), 3.66 (1 H, apparent s,
CH(OH)), 4.14 (1 H, qd, J 6.8, 1.2, CHCH3), 4.96–4.99 (2 H, m,
325 (MHϩ, 34), 255 (100), 243 (20), 216 (82), 78 (19); Accurate
ϩ
mass (CIϩ): Found 342.1891, C20H28NO2Si (MNH4 ) requires
C(CH )᎐CH ), 7.33–7.49 (6 H, m, Ph), 7.57–7.61 (2 H, m, Ph),
᎐
3
2
342.1889.
7.68–7.71 (2 H, m, Ph); δC (100 MHz, CDCl3) 8.2, 20.8, 22.0,
46.3, 71.9, 73.2, 111.1, 127.9, 128.2, 130.1, 130.3, 134.3, 134.4,
ϩ
[(3-Methylbut-2-enyl)diphenylsilanyloxy]phenylacetaldehyde
148.5; m/z (CIϩ) 342 (MNH4 , 87%), 325 (MHϩ, 20), 299 (85),
(15)
291 (44), 279 (50), 247 (61), 226 (19), 217 (65), 209 (88), 172
(100), 150 (71); Accurate mass (CIϩ): Found 342.1878,
Ester 13 (836 mg, 1.93 mmol) was dissolved in a mixture of
dichloromethane (4 mL) and heptane (6 mL) and cooled to
Ϫ78 ЊC. Di(isobutyl)aluminium hydride (1.94 mL, 1.0 M in
hexanes, 1.94 mmol) was added dropwise and the solution was
stirred at Ϫ78 ЊC for 1 h. Water (5 mL) was added, the solution
was warmed to room temperature and then partitioned between
ether (10 mL) and saturated aqueous Na2SO4 solution (10 mL).
The aqueous layer was extracted with ether (20 mL), the com-
bined organic extracts were washed with brine (20 mL) and
dried over MgSO4. The solvent was removed under reduced
pressure and the resulting oil was purified by flash column
chromatography on silica gel (25 : 1, petrol : ether) to give the
product as a colourless oil (425 mg, 57%). Rf 0.46 (4 : 1 petrol :
ether); νmax/cmϪ1 (film) 3070m, 3027m, 2966m, 2913m, 1737s,
1590w, 1490w, 1452m, 1429s, 1376w, 1118s br, 1073m, 923w,
857w, 733m, 699s; δH (200 MHz, CDCl3) 1.37 (3 H, s, CH3),
1.62 (3 H, s, CH3), 2.11 (2 H, apparent d, apparent J 8.1,
ϩ
C20H28NO2Si (MNH4 ) requires 342.1889.
2-Oxa-1,1,3-triphenyl-5-(propen-2-yl)silinan-4-ol (17) and (19)
To a solution of aldehyde 15 (264 mg, 0.68 mmol) in dichloro-
methane (10 mL) at room temperature was added dimethyl-
aluminium chloride (690 µL, 1 M in hexanes, 0.69 mmol). After
30 min a saturated aqueous Na2SO4 solution (10 mL) was
added and the mixture was extracted with ether (2 × 30 mL).
The combined organic extracts were washed with brine (20 mL)
and dried over MgSO4. The solvent was removed under reduced
pressure and the resulting oil was purified by flash column
chromatography on silica gel (15 : 1, petrol : ether) to give the
major product (17) as a colourless oil (151 mg, 57%) and the
minor product (19) as a colourless oil (21 mg, 8%). Data for 17:
Rf 0.23 (10 : 1 petrol : ether); νmax/cmϪ1 (film) 3458m br, 3069m,
2974s, 2926m, 2874s, 1958w, 1888w, 1823w, 1644w, 1590w,
1453m, 1429s, 1380m, 1305w, 1261w, 1174m, 1117s, 1058s,
1026s, 998m, 944w, 861s, 770m, 737s, 699s; δH (400 MHz,
CDCl3) 1.43–1.51 (2 H, m, SiCH2), 1.79 (3 H, s, CH3),
2.75 (1 H, ddd, J 10.4, 8.6, 6.8, CHCH2), 3.53 (1 H, dd, J 10.4,
8.7, CH(OH)), 4.72 (1 H, d, J 8.7, PhCH ), 4.90 (2 H, s,
SiCH ), 5.11 (1 H, d, J 1.8, PhCH ), 5.17 (1 H, br t, J 8.1, CH᎐
᎐
2
C), 7.22–7.52 (11 H, m, Ph), 7.56–7.67 (4 H, m, Ph), 9.64 (1 H,
J 1.8, CHO); δC (50 MHz, CDCl3) 16.2, 17.6, 25.7, 80.4, 116.8,
126.7, 127.9, 128.7, 130.2, 131.8, 133.9, 134.8, 136.1, 198.9; m/z
(EIϩ) 319 (Mϩ Ϫ C5H9, 32%), 199 (84), 139 (33), 105 (100), 77
(89); Accurate mass (CIϩ): Found 404.2051, C25H30NO2Si
C᎐CH ), 7.36–7.74 (15 H, m, Ph); [For 19: δ (400 MHz,
᎐
2
H
ϩ
(MNH4 ) requires 404.2046.
CDCl3) 1.11–1.32 (2 H, m, SiCH2), 1.86 (3 H, s, CH3), 2.70
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 5 8 – 3 7 6 7
3763