stable oil which was immediately reacted with ethane-1,2-diol
(0.36 ml, 6.5 mmol), toluene-p-sulfonic acid (1 crystal) and
toluene (50 ml) in a Dean–Stark apparatus until no more water
was collected. The toluene was removed in vacuo and the
residue chromatographed on silica gel (1:5 ethyl acetate–
hexane) to give the title compound, 14 as a colourless oil (1.7 g,
85%); Rf (30% EtOAc–hexane) 0.4; νmax/cmϪ1 2927 (m, C–H),
0.7, H-4), 7.24 (1H, td, J 7.5, 1.2, H-6), 7.06 (1H, s, H-1Ј), 7.01
(1H, td, J 7.5, 1, H-5), 6.77 (1H, d, J 7.5, H-7), 5.85 (1H, m,
H-2Љ), 5.21 (2H, m, H-3Љ), 4.36 (2H, dt, J 5.3, 1.7, H-1Љ), 1.00
(9H, s, SiC(CH3)3), 0.31 (6H, s, Si(CH3)2); δC(CDCl3) 166.7
(C᎐O), 142.9 (C-7a), 142.2 (C-3a), 138.3 (C-4), 131.8 (C-2Љ),
᎐
129.7 (C-6), 123.4 (C-3), 121.9 (C-5), 120.1 (C-1Ј), 117.3 (C-1Љ),
108.8 (C-7), 42.1 (2C, CH2, C-3Љ), 26.5 (SiC(CH3)3), 17.2
(SiC(CH3)3), Ϫ6.1 (Si(CH3)2); m/z 299 (7.4%, Mϩ), 242 (100,
Mϩ Ϫ C4H9), 186 (75%) (Found: Mϩ, 299.1695. C18H25NOSi
requires M 299.1705).
1652 (s, C᎐O); δ (360 MHz; CDCl ) 7.64 (1H, dd, J 8, 1.5,
᎐
H
3
H-3), 7.48 (1H, dd, J 8, 1.5, H-6), 7.35 (1H, td, J 8, 1.5, H-4),
7.21 (1H, td, J 8, 1.5, H-5), 5.18 (1H, dd, J 5.3, 4.4, H-2Љ), 4.38
(1H, dd, J 14.2, 4.4, H-1Љ), 3.90 (4H, m, OCH2CH2O), 3.25
(1H, dd, J 14.2, 5.3, H-1Љ), 0.67 (9H, s, C(CH3)3), Ϫ0.07 (3H,
E-Isomer. A green oil (74 mg, 10%), Rf (30% EtOAc–hexane)
0.49; νmax/cmϪ1 2927 (m, C–H), 1703 (s, C᎐O) 1610 (s, C᎐C),
᎐
᎐
s, Si–CH ), Ϫ0.09 (3H, s, Si–CH ); δ (CDCl ) 154.0 (C᎐O),
1468 (s, benzene ring); δH(360 MHz; CDCl3) 7.58 (1H, d, J 7.6,
H-4), 7.31 (1H, s, H-1Ј), 7.25 (1H, td, J 7.6, 1.1, H-6), 7.01
(1H, td, J 7.6, 1, H-5), 6.81 (1H, d, J 7.6, H-7), 5.84 (1H,
m, H-2Љ), 5.23 (2H, m, H-3Љ), 4.39 (2H, dt, J 5.2, 1.6, H-1Љ), 1.02
(9H, s, SiC(CH3)3), 0.33 (6H, s, Si(CH3)2); δC(CDCl3) 166.0
᎐
3
3
C
3
141.0 (C-1), 133.3 (C-3), 132.2 (C-6), 130.0 (C-5), 128.1 (C-4),
124.1 (C-2), 101.0 (C-2Љ), 97.0 (C-2Ј), 96.8 (C-3Ј), 64.9, 64.8
(OCH2CH2O), 49.8 (C-1Љ), 25.7 (C-(CH3)3), 16.2 (C-(CH3)3),
Ϫ5.4 (Si-Me2); m/z 425 (29%, Mϩ, 81Br), 423 (29%, Mϩ, 79Br),
167 (35), 73 (100) (Found: Mϩ (79Br) 423.0886. C19H2679BrNO3Si
requires M 423.0865).
(C᎐O), 148.0 (C-7a), 144 (C-3a), 137.8 (C-4), 131.6 (C-2Љ),
᎐
129.8 (C-6), 123.8 (C-1Ј), 122.5 (C-3), 121.8 (C-5), 117.5 (C-1Љ),
109.1 (C-7), 42.4 (2C, CH2, C-3Љ), 26.3 (SiC(CH3)3), 18.0
(SiC(CH3)3), Ϫ5.4 (Si(CH3)2); m/z 299 (9%, Mϩ), 242 (100,
Mϩ Ϫ C4H9) (Found: Mϩ, 299.1697. C18H25NOSi requires M
299.1705).
Radical cyclisations: general procedure
The amide in toluene was heated at 80 ЊC under argon. AIBN
(0.1 equivalents) and tributyltin hydride were then added simul-
taneously, dropwise. AIBN (0.1 equivalents) was then added
every hour for 3 hours. The reaction was then allowed to stir
overnight at 80 ЊC. Toluene was removed in vacuo. The residue
was dissolved in ethyl acetate and washed with 20% ammonia
solution (5 × 100 ml). The organic layer was dried (MgSO4)
and the solvent removed in vacuo.
N-(1,3-Dioxolan-2-ylmethyl)-3-tert-butyldimethylsilylmethyl-
ideneindol-2(3H)-one, 15. Amide 14 (1.7 g, 3.99 mmol) and
tributyltin hydride (1.28 g, 4.38 mmol) gave 15 as a mixture
of E- and Z-isomers separable by chromatography (SiO2, 3%
EtOAc–hexane).
Z-Isomer. A green oil (0.62 g, 45%), Rf (30% EtOAc–hexane)
0.67; νmax/cmϪ1 3054 (olefinic C–H), 2926 (C-H), 1652 (tertiary
N-Methyl-3-tert-butyldimethylsilylmethylideneindol-2(3H)-
one, 10a. Amide 9a (0.2 g, 0.57 mmol) and tributyltin hydride
(0.17 ml, 0.63 mmol) gave 10a as a mixture of E- and Z-isomers
which were separable by chromatography (SiO2, 2% EtOAc–
hexane).
amide C᎐O), 1456 (benzene ring), 1265 (C–O); δ (360 MHz;
᎐
H
CDCl3), 7.43 (1H, d, J 7.6, H-4), 7.26 (1H, td, J 7.6, 1.0, H-6),
7.04 (1H, s, H-1Ј), 7.02 (1H, d, J 7.6, H-5), 6.99 (1H, t, J 7.6,
H-7), 5.15 (1H, t, J 4.1, H-2Љ), 3.97 (2H, m, H-4Љ or H-5Љ), 3.91
(2H, d, J 4.1, H-1Љ), 3.87 (2H, m, H-4Љ or H-5Љ), 0.99 (9H, s,
Si(CH3)3), 0.30 (6H, s, 2 × Si(CH3)); δC(CDCl3) 138.3 (C-4),
129.8 (C-6), 127.2 (C-3), 121.9 (C-5), 120.0 (C-1Ј), 109.3 (C-7),
101.9 (C-2Љ), 65.2 (CH2), 42.9 (C-1Љ), 26.5 (SiC(CH3)3), 17.2
(SiC(CH3)3), Ϫ6.2 (Si(CH3)2); m/z 346 (33%, Mϩ ϩ1), 345 (100,
Mϩ), 288 (65, Mϩ Ϫ C4 H9) (Found: Mϩ 345.1780. C19H27NO3Si
requires M 345.1760).
Z-Isomer. A green solid (71 mg, 46%), mp 84–86 ЊC; Rf (30%
EtOAc–hexane) 0.56; νmax/cmϪ1 2925 (m, C–H), 1703 (s, C᎐O),
᎐
1611 (s, C᎐C), 1469 (s, benzene ring); δ (360 MHz; CDCl ) 7.43
᎐
H
3
(1H, dd, J 7.5, 0.6, H-4), 7.27 (1H, td, J 7.5, 1.1, H-6), 7.03 (1H,
s, H-1Ј), 7.01 (1H, td, J 7.5, 0.8, H-5), 6.76 (1H, d, J 7.5, H-7),
3.21 (3H, s, NMe), 1.00 (9H, s, C(CH3)3), 0.31 (6H, s, 2(CH3));
δ (CDCl ) 167.1 (C᎐O), 143.5 (C-7a), 142.3 (C-3a), 138.0
᎐
C
3
E-Isomer. A green oil (0.3 g, 22%), Rf (30% EtOAc–hexane)
0.54; νmax/cmϪ1 3054 (olefinic C–H), 2926 (C–H), 1652 (tertiary
(C-4), 129.8 (C-6), 123.2 (C-3), 121.9 (C-5), 120.0 (C-1Ј), 107.9
(C-7), 26.5 (C-(CH3)3), 25.8 (N-CH3), 17.1 (C-(CH3)3), Ϫ6.2
(Si-Me2); m/z 273 (12.2%, Mϩ), 258 (52.3, Mϩ Ϫ CH3), 216
(100, Mϩ Ϫ C(CH3)3), 201 (54.4), 186 (70.4), 158 (35) (Found:
Mϩ, 273.1541. C16H23NOSi requires M 273.1549).
amide C᎐O), 1456 (benzene ring), 1265 (C–O); δ (360 MHz;
᎐
H
CDCl3), 7.56 (1H, d, J 7.3, H-4), 7.30 (1H, s, H-1Ј), 6.99–7.13
(3H, m, H-5, H-6, H-7), 5.13–5.17 (1H, m, H-2Љ), 3.97 (2H,
m, H-4Љ or H-5Љ), 3.95 (2H, d, J 4.1, H-1Љ), 3.87 (1H, m, H-4Љ
or H-5Љ), 1.01 (9H, s, Si(CH3)3), 0.32 (6H, s, 2 × Si(CH3));
E-Isomer. A green solid (25 mg, 16%), Rf (30% EtOAc–
hexane) 0.50; νmax/cmϪ1 2929 (C-H), 1708 (s, C᎐O), 1611 (s,
᎐
δ (CDCl ) 166.8 (C᎐O), 144.4 (C-7a), 141.5 (C-3a), 137.7 (C-4),
᎐
C
3
C᎐C), 1470 (s, benzene ring), 1265 (s, Si–C); δ (360 MHz;
᎐
H
129.8 (C-6), 128.0 (C-3), 123.6 (C-1Ј), 121.8 (C-5), 109.4 (C-7),
101.7 (C-2Љ), 65.1 (CH2), 42.9 (C-1Љ), 26.4 (SiC(CH3)3), 17.3
(SiC(CH3)3), Ϫ5.4 (Si(CH3)2); m/z 345 (17.6%, Mϩ), 288 (100,
Mϩ Ϫ C4H9) (Found: Mϩ 345.1783. C19H27NO3Si requires M
345.1760).
CDCl3) 7.57 (1H, d, J 7.6, H-4), 7.30 (1H, s, H-1Ј), 7.29 (1H,
t, J 7.6, H-6), 7.02 (1H, t, J 7.6, H-5), 6.81 (1H, d, J 7.6, H-7),
3.24 (3H, s, NMe), 1.01 (9H, s, C(CH3)3), 0.32 (6H, s, 2(CH3));
δ (CDCl ) 167.1 (C᎐O), 145.0 (C-7a), 141.8 (C-3a), 137.5
᎐
C
3
(C-4), 129.9 (C-6), 123.7 (C-3), 122.6 (C-1Ј), 121.8 (C-5),
108.5 (C-7), 29.7 (N-Me), 26.9 (C-(CH3)3), 17.4 (C-(CH3)3),
Ϫ5.4 (Si-Me2); m/z 273 (35.6%, Mϩ), 258 (13.9, Mϩ Ϫ CH3),
216 (85.6, Mϩ Ϫ C(CH3)3), 201 (7.8), 186 (41.5), 158 (4.4),
28.0 (100) (Found: Mϩ, 273.1544. C16H23NOSi requires M
273.1549).
N-Methyl-3Ј-(tert-butyldimethylsilyl)spiro[indole-3,2Ј-
oxiran]-2-one, 16a. MCPBA (0.14 g, 50% w/v, 0.4 mmol) was
added portionwise to a solution of Z-10a (0.1 g, 0.37 mmol)
in dichloromethane (5 ml) at room temperature. The reaction
mixture was stirred for 16 hours after which time a further
quantity of MCPBA (0.14 g) was added. The reaction mixture
was stirred for a further 2 hours and then sodium sulfite
solution (10 ml, 10% w/v) was added to quench the reaction.
The organic layer was washed with saturated sodium
bicarbonate solution (3 × 5 ml), water (3 × 5 ml) and finally
brine (3 × 5 ml). The organic layer was dried and evaporated
under reduced pressure. Chromatography (SiO2, 15% EtOAc–
hexane) gave the title compound, 16a as a pale yellow oil (0.045
g, 43%); Rf (3:7 EtOAc–hexane) 0.52; νmax/cmϪ1 2928 (C–H),
N-(Prop-2-enyl)-3-tert-butyldimethylsilylmethylideneindole-2-
(3H)-one, 10b. Amide 9b (0.9 g, 2.38 mmol) and tributyltin
hydride (0.75 g, 2.61 mmol) gave 10b as a mixture of E- and
Z-isomers which were separable by chromatography (SiO2, 3%
EtOAc–hexane).
Z-Isomer. A green oil (0.35 g, 49%), Rf (30% EtOAc–hexane)
0.56; νmax/cmϪ1 2927 (m, C–H), 1705 (s, C᎐O), 1610 (s, C᎐C),
᎐
᎐
1470 (s, benzene ring); δH(360 MHz; CDCl3) 7.45 (1H, dd, J 7.5,
J. Chem. Soc., Perkin Trans. 1, 2000, 763–768
767