Reactions of Allylsilanes with Alkyl Halides
FULL PAPER
08C then for 1 h at RT, then quenched at 08C with saturated aqueous
NH4Cl (20 mL). The organic layer was separated and the aqueous layer
was extracted with Et2O (2 ꢂ). The combined extracts were dried over
MgSO4 and concentrated under reduced pressure. The crude product was
filtered through a short pad of silica (petroleum ether), affording 1b as a
white solid (5.7 g, 94%).[28] Rf =1 (Petroleum ether); m.p. 1318C;
1H NMR (200 MHz, CDCl3): d=4.59 (s, 1H), 4.55 (s, 1H), 1.77 (s, 2H),
1.75 (s, 3H), 0.18 ppm (s, 27H); 13C NMR (50 MHz, CDCl3): d=146.2,
Method 2: General procedure C was followed using AdBr 4a (43 mg,
0.2 mmol), sulfonyloxime 3a (137 mg, 0.5 mmol, mixture of E/Z
isomer),[17] allylthioether 1c (320 mg, 1 mmol), and AIBN (ca. 17 mg,
0.1 mmol). Purification using silica gel (petroleum ether/EtOAc, 98:2) af-
forded the product 5a contaminated with silicon impurities, then allylsul-
fone 2b (petroleum ether/EtOAc, 80:20) as a yellow oil (73 mg, ratio 5a/
2b, 1:2.25). Compound 5a was then treated according to general proce-
dure B. Purification using silica gel (petroleum ether/EtOAc, 98:2) gave
5a (48 mg, 89%).
Compound 5a: Rf =0.35 (Petroleum ether/EtOAc, 98:2); 1H NMR
(200 MHz, CDCl3): d=7.39–7.28 (m, 5H), 7.22 (s, 1H), 5.04 (s, 2H), 2.01
(br.s, 3H), 1.79–1.64 ppm (m, 12H); 13C NMR (50 MHz, CDCl3): d=
158.9, 137.8, 128.5, 128.4, 127.9, 75.7, 40.1, 36.7, 35.8, 28.0 ppm; IR (neat):
n˜ =2904, 2848, 1725, 1626, 1441, 1298, 1192, 1209, 1175, 1135, 942,
836 cmÀ1; HRMS (ESI): m/z calcd for C18H23NONa: 292.1677 [M+Na]+;
found: 292.1679.
108.9, 24.9, 18.6, 1.1 ppm. IR (neat): n˜ =2949, 2894, 1244, 825, 685 cmÀ1
HRMS (EI): m/z calcd for C13H34Si4: 302.1737 [M]+; found: 302.1736.
;
2-(Allylthio)-1,1,1,3,3,3-hexamethyl-2-(trimethylsilyl)trisilane
(1c):
TMSCl (2.83 g, 10 mmol) was added in one portion to a mixture of prop-
2-ene-1-thiol (4.16 mL, 50 mmol) and triethylamine (1.6 mL, 12 mmol), in
Et2O (50 mL). The solution was stirred for 1 h at RT, then aqueous HCl
(20 mL, 1m) was added. The organic layer was extracted with Et2O (3 ꢂ),
dried over MgSO4, and concentrated under vacuum. Purification by silica
gel chromatography (petroleum ether) afforded 1c as a white semi-solid
(2.11 g, 66%). Rf =0.6 (Petroleum ether); 1H NMR (200 MHz, CDCl3):
d=5.98–5.78 (m, 1H), 5.20–4.99 (m, 2H), 3.18–3.13 (m, 2H), 0.23 ppm (s,
27H); 13C NMR (50 MHz, CDCl3): d=136.9, 116.0, 33.4, 0.9 ppm; IR
(neat): n˜ =2950, 2894, 1637, 1244, 986, 825, 745, 687 cmÀ1; HRMS (EI):
m/z calcd for C12H32SSi4Na: 343.1199 [M+Na]+; found: 343.1196.
Compound 2b: All data matched those of a sample prepared according
to a reported procedure.[29] Rf =0.4 (petroleum ether/EtOAc, 80:20);
1H NMR (300 MHz, CDCl3): d=7.89–7.86 (m, 2H), 7.66–7.61 (m, 1H),
7.56–7.51 (m, 2H), 5.02 (s, 1H), 4.67 (s, 1H), 3.76 (s, 2H), 1.86 ppm (s,
3H).
Representative example of vinylation—Method 1: General procedure A
was followed using AdBr 4a (43 mg, 0.2 mmol), vinyl sulfone 3b (73 mg,
0.3 mmol), allyl tris(trimethylsilyl)silane (1b; 302 mg, 1 mmol), and
DTBP (12 mg, 0.08 mmol) in tert-butylbenzene (2.4 mL). Purification
using silica gel (petroleum ether) afforded 6a contaminated by silicon im-
purities and vinylsilane 9. Product 6a was treated according to general
procedure B. Purification using silica gel (petroleum ether) gave 6a
Addition of halogenated species onto sulfones mediated by allyl tris(tri-
ACHTUNGTRENNUNGmethACHTUNGTRENNUNGylsilyl)silane (1b)—general procedure A: Allyl tris(trimethylsilyl)si-
lane (1b; 1 mmol, 5 equiv), alkyl iodide or bromide (0.2 mmol, 1 equiv),
sulfone (0.3 mmol, 1.5 equiv for sulfonyloxime and vinyl sulfone;
0.6 mmol, 3 equiv for allylsulfone), and DTBP (0.08 mmol, 0.4 equiv)
were mixed in tert-butylbenzene (2.4 mL). The mixture was rigorously
degassed three times by freeze–pump–thaw cycles. The reaction was then
heated at 1408C for 3 h, then cooled to RT and tert-butylbenzene was
evaporated under high vacuum. Purification by flash column chromatog-
raphy with silica gel afforded the desired product. If the product was con-
taminated with silicon impurities after chromatography, general proce-
dure B was subsequently followed.
(30.5 mg, 64%) as
(29 mg, 60%).
a
solid, which was recrystallized from methanol
Method 2: General procedure
C
was followed using AdBr (43 mg,
0.2 mmol), vinyl sulfone 3b (122 mg, 0.5 mmol), allylthioether 1c
(320 mg, 1 mmol), and AIBN (ca. 17 mg, 0.1 mmol). Purification using
silica gel (petroleum ether) afforded 6a contaminated by silicon impuri-
ties. Product 6a was directly recrystallized from methanol (32 mg, 67%).
Removal of silicon impurities from final products—general procedure
B:[16] The previously purified product was dissolved in a 1:1 mixture of
MeOH/THF (2 mL) and H2O2 (0.5 mL, 35%, 30 equiv), KF (116 mg,
10 equiv), and KHCO3 (200 mg, 10 equiv) were added. The reaction mix-
ture was stirred overnight at RT then H2O (4 mL) and EtOAc (4 mL)
were added. The organic layer was separated then washed successively
with Na2S2O3 (2 mL, 1m in H2O) and saturated aqueous NaCl (2 mL).
The aqueous layer was extracted with CH2Cl2 (2 ꢂ) then the combined
organic layers were dried over MgSO4 and the solvents evaporated under
vacuum. Purification by flash column chromatography with silica gel af-
forded the pure product.
Compound 6a: Rf =0.85 (Petroleum ether); m.p. 708C (MeOH);
1H NMR (200 MHz, CDCl3): d=7.40–7.14 (m, 5H), 6.26 (d, J=16.3 Hz,
1H), 6.11 (d, J=16.3 Hz, 1H), 2.03 (br.s, 3H), 1.81–1.69 ppm (m, 12H);
13C NMR (50 MHz, CDCl3): d=142.2, 138.3, 128.5, 126.8, 126.1, 124.6,
42.3, 37.0, 35.3, 28.6 ppm; IR (neat): n˜ =2904, 2848, 1451, 966, 909, 735,
693 cmÀ1; HRMS (ESI): m/z calcd for C18H22Na: 259.1098 [M+Na]+;
found: 259.1101.
Allylation reaction—typical procedure: General procedure A was fol-
lowed with AdBr 4a (43 mg, 0.2 mmol), allylsulfone 3c (144 mg,
0.6 mmol), allyl tris(trimethylsilyl)silane 1b (302 mg, 1 mmol), and DTBP
(12 mg, 0.08 mmol) in tert-butylbenzene (2.4 mL). Purification using silica
gel (petroleum ether/EtOAc, 80:20) afforded allyl tris(trimethylsilyl)si-
lane 8 (13 mg, 23%) as the first eluted product, then the expected prod-
uct 7a contaminated by silicon impurities. Product 7a was treated accord-
ing to general procedure B and purified using silica gel (petroleum ether/
EtOAc, 80:20) affording 7a (40 mg, 85%).
Compound 7a: Rf =0.33 (pentane/CH2Cl2, 80:20); 1H NMR (300 MHz,
CDCl3): d=6.18 (d, J=1.9 Hz, 1H), 5.41–5.40 (m, 1H), 3.73 (s, 3H), 2.14
(s, 2H), 1.92 (br. s, 3H), 1.68–1.55 (m, 6H), 1.44 ppm (app. d, J=2.6 Hz,
6H); 13C NMR (50 MHz, CDCl3): d=168.8, 137.3, 127.3, 51.9, 45.6, 42.1,
37.0, 33.3, 28.8 ppm; IR (neat): n˜ =2901, 2847, 1722, 1440, 1209, 1174,
1134, 942, 836 cmÀ1; HRMS (ESI): m/z calcd for C15H22O2Na: 257.1517
[M+Na]+; found: 257.1516.
Addition of halogenated species onto sulfones mediated by 3-tris(trime-
thylsilyl)silylthiopropene (1c)—general procedure C: Benzene (2 mL;
rigorously degassed three times by freeze–pump–thaw cycles) was added
to allylthioether 1c (1 mmol, 5 equiv), alkyl bromide (0.2 mmol, 1 equiv),
and sulfone (0.5 mmol, 2.5 equiv). AIBN (0.1 mmol, 0.5 equiv) dissolved
in benzene (1 mL; rigorously degassed three times by freeze–pump–thaw
cycles) was added with a syringe-pump over 15 h to the solution, which
was heated at 808C. The solution was then cooled to RT and benzene
was evaporated under reduced pressure. Purification by flash column
chromatography using silica gel afforded the desired product. If the prod-
uct was contaminated with silicon impurities after the chromatography,
general procedure B was subsequently followed.
Representative example of oximation—Method 1: General procedure A
was followed using AdBr 4a (43 mg, 0.2 mmol), sulfonyloxime 3a
Compound 8: Rf =0.5 (pentane/CH2Cl2, 80:20); 1H NMR (200 MHz,
CDCl3): d=5.95 (d, J=1.4 Hz, 1H), 5.42–5.40 (m, 1H), 3.71 (s, 3H), 2.05
(d, J=1.2 Hz, 2H), 0.15 ppm (s, 27H); 13C NMR (50 MHz, CDCl3): d=
167.8, 141.3, 122.0, 51.8, 12.1, 1.2 ppm; IR (neat): n˜ =2955, 2892, 1726,
(82.5 mg, 0.3 mmol,
E
isomer),[17] allyl tris(trimethylsilyl)silane (1b;
302 mg, 1 mmol), and DTBP (12 mg, 0.08 mmol) in tert-butylbenzene
(2.4 mL). Purification using silica gel (petroleum ether/EtOAc, 98:2) af-
forded the product 5a contaminated by silicon impurities, then allylsul-
fone 2b (petroleum ether/EtOAc, 80:20) as a pure yellow oil (37.7 mg,
96%). Compound 5a was treated according to general procedure B. Pu-
rification using silica gel (petroleum ether/EtOAc, 98:2) led to compound
5a (50 mg, 92%).
1724, 1250, 833, 754, 688 cmÀ1
;
HRMS (ESI): m/z calcd for
C14H34O2Si4Na: 369.1533 [M+Na]+; found: 369.1532.
Vinyltris(trimethylsilyl)silane (9): General procedure A was followed
with vinyl sulfone 3b (49 mg, 0.2 mmol), allyl tris(trimethylsilyl)silane 1b
(302 mg, 1 mmol), and DTBP (12 mg, 0.08 mmol) in tert-butylbenzene
Chem. Eur. J. 2011, 17, 13904 – 13911
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
13909