Alkyltelluride-Mediated Tandem SRN1/SHi Reactions
J . Org. Chem., Vol. 64, No. 18, 1999 6769
34.3, 43.4, 109.9, 120.5, 124.1, 128.7, 131.0, 160.0; 125Te NMR
δ 202; HRMS calcd for C13H18O130Te 320.0420, found 320.0425.
Rea ction of 20a w ith Sod iu m n -Bu tyltellu r ola te: P r ep a -
r ation of Ben zo[b]tellu r oph en e19,20 (23) an d 2-(2-Iodoph e-
n yl)eth a n ol30 (21). Oxirane (20a ) (49 mg, 0.21 mmol) was
reacted according to the standard protocol (A) with di-n-butyl
ditelluride (145 mg, 0.33 mmol) and sodium borohydride (27
mg, 0.72 mmol). Flash chromatography (90:10 petroleum ether/
ether) afforded a 1:1 mixture of compounds consistent with
21 and 22. The crude mixture was dissolved in benzene (1.5
mL), p-toluenesulfonic acid (ca. 5 mg) added, and the mixture
heated at reflux for 30 min. Workup and vacuum chromatog-
raphy afforded 2-(2-iodophenyl)ethanol (21) and benzo[b]-
tellurophene (23) exhibiting NMR spectral data identical to
those previously reported.19,20,28
Sch em e 5
2-(2-Iodophenyl)ethanol (21): 1H NMR δ 3.03 (2H, t, J )
6.6 Hz), 3.87 (2H, t, J ) 6.6 Hz), 6.89-6.95 (2H, m), 7.23-
7.26 (2H, m), 7.84 (1H, d, J ) 8.4 Hz).
Benzo[b]tellurophene (23): 1H NMR δ 7.15 (1H, t, J ) 7.2
Hz), 7.38 (1H, t, J ) 7.8 Hz), 7.85 (1H, d, J ) 6.9 Hz), 7.97
(2H, d, J ) 7.2 Hz), 8.71 (1H, d, J ) 6.8 Hz); 125Te NMR δ
727.
Rea ction of 20b w ith Sod iu m n -Bu tyltellu r ola te: 2-(2-
Iod op h en yl)-2-p h en yla ceta ld eh yd e (24). Oxirane (20b) (56
mg, 0.174 mmol) was reacted according to the standard
protocol (A) with di-n-butyl ditelluride (119 mg, 0.269 mmol)
and sodium borohydride (22 mg, 0.587 mmol). Flash chroma-
tography (90:10 petroleum ether/ether) afforded 24 as a pale
oil (25 mg, 45%): 1H NMR δ 5.40 (1H, s), 6.99 (1H, t, J ) 7.8
Hz), 7.18-7.32 (5H, m), 7.62 (1H, t, J ) 7.2 Hz), 7.82 (2H, d,
J ) 7.8 Hz), 9.98 (1H, s); HRMS calcd for C13H10IO 308.9776,
found 308.9780.
Eth yl 3-(ter t-Bu tyld im eth ylsilyloxy)p h en yla ceta te. To
a solution of tert-butylchlorodimethylsilane (2.70 g, 17.8 mmol)
in DMF (8 mL) at ambient temperature were added imidazole
(3.03 g, 44.5 mmol) and ethyl 3-hydroxyphenylacetate (3.20
g, 17.8 mmol) under an atmosphere of dry nitrogen. The
resulting mixture was then stirred at ambient temperature
for 72 h. Standard workup (addition of water, extraction with
diethyl ether (3×), washing with water, brine, drying (MgSO4),
and concentration in vacuo) afforded the title compound (5.14
g, 98%), which was isolated as a pale yellow oil and was used
in the next step without further purification: 1H NMR δ 0.20
(6H, s), 0.98 (9H, s), 1.25 (3H, t, J ) 7.1 Hz), 3.55 (2H, s), 4.14
(2H, q, J ) 7.1 Hz), 6.75 (1H, m), 6.78 (1H, m), 6.87 (1H, m),
7.17 (1H, t, J ) 7.8 Hz); 13C NMR δ -4.4, 14.2, 18.2, 25.7,
41.4, 60.8, 118.7, 121.0, 122.2, 129.4, 135.5, 155.7, 171.4. MS
m/z (relative intensity) 294 (M+, 66.4). Anal. Calcd for C16H26O3-
Si: C, 65.26; H, 8.90. Found: C, 65.08; H, 8.88.
ter t-Bu tyldim eth ylsilyl 3-(2-Hydr oxyeth yl)ph en yl Eth er
(34). To a solution of ethyl 3-(tert-butyldimethylsilyloxy)-
phenylacetate (2.50 g, 8.49 mmol) in dry diethyl ether (80 mL)
was added LiAlH4 (0.400 g, 10.2 mmol) in one portion at -20
°C under an atmosphere of dry nitrogen. After 70 min of
stirring at 0 °C, the reaction was quenched by addition of
aqueous HCl (1 M) and the organic layer separated. Standard
workup afforded the title compound (2.07 g, 96%) as a pale
yellow oil, which was used in the next step without further
purification: 1H NMR δ 0.20 (6H, s), 0.98 (9H, s), 1.43 (1H,
s(br)) 2.82 (2H, t, J ) 6.6 Hz), 3.84 (2H, m), 6.69-6.73 (2H,
m), 6.82 (1H, m), 7.17 (1H, dd, J ) 8.8, 7.5 Hz); 13C NMR δ
-4.4, 18.2, 25.7, 39.1, 63.6, 118.1, 120.8, 121.9, 129.5, 139.9,
155.8. MS m/z (relative intensity) 252 (M+, 37.5). Anal. Calcd
for C14H24O2Si: C, 66.61; H, 9.58. Found: C, 66.34; H, 9.70.
ter t-Bu tyld im eth ylsilyl 3-(2-Hyd r oxyeth yl)-4-iod op h e-
n yl Eth er . A solution of iodine (1.82 g, 7.17 mmol) in
chloroform (30 mL) was added dropwise to a magnetically
stirred solution of compound 34 (1.81 g, 7.17 mmol) and silver
trifluoroacetate (1.59 g, 7.17 mmol) in chloroform (40 mL)
under an atmosphere of dry nitrogen. The reaction was then
stirred at ambient temperature for 2.5 h. After filtration from
reaction vessel was purged with nitrogen, and methanol (ca.
1 mL) was added dropwise, with caution, until a persistent
pale yellow solution was obtained. 1-(2-Iodophenyl)-1-methyl-
oxirane (12) (118 mg, 0.45 mmol) in THF (1 mL) was added
rapidly and the resultant mixture stirred overnight while
shielded from background light. Water (5 mL) was added, the
product was extracted into ether (3 × 10 mL), the combined
extracts were dried (MgSO4), and the solvent was removed in
vacuo. The residue was purified by flash chromatography (85:
15 petroleum ether/ether to give 13 as a yellow solid (74 mg,
62%): mp ) 71-73 °C; 1H NMR δ 1.71 (3H, s), 2.43 (1H, s(br)),
3.74 (1H, d, J ) 10.5 Hz), 3.79 (1H, d, J ) 10.5 Hz), 7.17-
7.24 (3H, m), 7.39-7.42 (1H, m); 13C NMR δ 23.8, 26.9, 86.4,
116.6, 125.7, 126.7, 129.1, 132.9, 151.7; 125Te NMR δ 418. Anal.
Calcd for C9H10OTe: C, 41.3; H, 3.9. Found: C, 41.7; H, 4.1.
3-Meth ylben zo[b]tellu r op h en e.19,20 A solution of 13 (17
mg, 65 µmol) and p-toluenesulfonic acid (ca. 10 mg) in benzene
(2 mL) was heated under reflux for 30 min. The solution was
cooled and the solvent removed in vacuo. Dichloromethane (5
mL) was added, the solution washed with water (2 × 5 mL)
and dried (MgSO4), and the solvent removed in vacuo to afford
the title compound (16 mg, 94%) as a yellow oil exhibiting
spectral data identical to those reported previously:19,20 1H
NMR δ 2.40 (3H, d, J ) 0.6 Hz), 7.22 (1H, t, J ) 7.8 Hz), 7.42
(1H, t, J ) 7.8 Hz), 7.69 (1H, d, J ) 8.1 Hz), 7.96 (1H, d, J )
7.7 Hz), 8.22 (1H, s); 13C NMR δ 19.8, 114.6, 124.5, 124.9,
126.2, 132.4, 143.0, 147.3; 125Te NMR δ 652.
2,3-D i h y d r o -3-h y d r o x y -3-m e t h y lb e n z o [b ]s e le n o -
p h en e (17) was prepared according to the standard protocol
(A) using 1-benzylseleno-2-(2-iodophenyl)propan-2-ol (5a , R )
Me) (106 mg, 0.25 mmol), di-n-butyl ditelluride (85 mg, 0.23
mmol), and sodium borohydride (35 mg, 0.93 mmol). Flash
chromatography (70:30 petroleum ether/ether) afforded 17 as
a pale yellow solid (39 mg, 74%): mp ) 69-70 °C; 1H NMR δ
1.63 (3H, s), 2.37 (1H, s(br)), 3.37 (1H, d, J ) 10.8 Hz), 3.43
(1H, d, J ) 10.8 Hz), 7.11-7.20 (3H, m), 7.25-7.28 (1H, m);
13C NMR δ 25.9, 41.0, 83.8, 124.3, 125.6, 126.5, 129.3, 134.8,
146.4; 77Se NMR δ 259. Anal. Calcd for C9H10OSe: C, 50.7; H,
4.7. Found: C, 50.6; H, 4.8.
3-(n -Bu tyltellu r o)m eth yl-2,3-dih ydr oben zo[b]fu r an (18)
was prepared according to the standard protocol (A) using
1-allyloxy-2-iodobenzene (15) (105 mg, 0.41 mmol), di-n-butyl
ditelluride (72 mg, 0.21 mmol), and sodium borohydride (21
mg, 0.56 mmol). Flash chromatography (95:5 petroleum ether/
ether) afforded 18 as an unstable yellow oil (22 mg, 17%): 1H
NMR δ 0.91 (3H, t, J ) 7.5 Hz), 1.31-1.43 (2H, m), 1.66-1.76
(2H, m), 2.64 (2H, t, J ) 7.5 Hz), 2.79 (1H, dd, J ) 6.1, 9.3
Hz), 3.07 (1H, dd, J ) 4.5, 12.0 Hz), 3.71-3.80 (1H, m), 4.29
(1H, dd, J ) 6.1, 9.3 Hz), 4.68 (1H, t, J ) 8.7 Hz), 6.79 (1H, d,
J ) 7.8 Hz), 6.87 (1H, t, J ) 7.5 Hz), 7.15 (1H, t, J ) 7.8 Hz),
7.23 (1H, d, J ) 7.5 Hz); 13C NMR δ 3.5, 7.5, 13.4, 25.1, 29.7,
(30) Acheson, R. M.; Lee, G. C. M. J . Chem. Soc., Perkin Trans. 1
1987, 2321.