A general synthesis of five, six and seven-membered silasultones via dehydrative cyclisation

Article abstract of DOI:10.1016/j.tet.2005.05.042

Five, six and seven-membered silasultones can be conveniently prepared in good yield by dehydrative cyclisation of siloxane disulphonic acids. The siloxanes are prepared by protodesilylation of the corresponding phenylsilane sulphonic acids. The sulphonate group is introduced either by free-radical sulphonation of vinyl silanes, or by S_N2 sulphite displacement of a long chain alkyl chloride.

Full text of DOI:10.1016/j.tet.2005.05.042

Tetrahedron 61 (2005) 7233–7240
A general synthesis of five, six and seven-membered silasultones
via dehydrative cyclisation
*
´ ˆ
D. Christopher Braddock and Jerome J.-P. Peyralans
Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, UK
Received 4 March 2005; revised 26 April 2005; accepted 12 May 2005
Available online 14 June 2005
Abstract—Five, six and seven-membered silasultones can be conveniently prepared in good yield by dehydrative cyclisation of siloxane
disulphonic acids. The siloxanes are prepared by protodesilylation of the corresponding phenylsilane sulphonic acids. The sulphonate group
is introduced either by free-radical sulphonation of vinyl silanes, or by SN2 sulphite displacement of a long chain alkyl chloride.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Silasultones are alicyclic structures containing the –Si–O–
SO2– molecular fragment. Silasultones have potential as
monomers in polymer chemistry and are the cyclic
equivalents of useful aliphatic reagents and catalysts such
as trimethylsilyl trifluoromethanesulphonate.1 However, the
silasultones as a class of compounds has been little
explored, and synthetic routes to them are severely limited.
Pre-existing methods for the preparation of silasultones
include only the formal insertion of SO3 into silacyclobu-
tanes,2a–f or the rearrangement of 1-silacyclopent-3-enes
and 3-silabicyclo[3.2.1]hexanes mediated by Me3SiOSO2-
Cl.2g The former method is restricted to the preparation of
six-membered silasultones from silacyclobutanes† since
attempted SO3 insertion into larger non-strained sila-rings
results in competitive attack at exo-Si–C bonds.1c The latter
method generally results in mixtures of compounds, and
necessarily leaves a(n) (unwanted) pendant alkene chain in
the silasultone product. Herein, we describe the first general
synthetic approach to silasultones of ring sizes of 5–7.‡
Silasultones 1–6 were prepared by dehydrative cyclisation
of disulphonic acid siloxanes (7–12) via vacuum sublima-
tion (Scheme 1). This method provides the silasultones 1–6
in good-to-moderate yields (ca. 65–45%). It was found to be
superior to attempted dehydrative cyclisation of the
disulphonic acids by azeotropic removal of water in
refluxing toluene which consistently generated a mixture
of silasultones and the corresponding unreacted diacids
even after extended heating (48 h).
With the exception of disulphonic acids 9 and 10, the
diacids 7–8, 11–12 were prepared by ipso-protodesilylation
of the corresponding phenylsilanes 13–16 followed by
treatment with a strong acid ion-exchange resin to ensure
complete protonation of the sulphonates. This two-step
procedure delivered the disulphonic acids in essentially
quantitative yields (Scheme 2). Aqueous hydrochloric acid
was a sufficiently acidic medium for ipso-protodesilylation
of methylsilanes 13 and 15, but the more sterically hindered
butylsilanes 14 and 16 required the use of a more powerful
acidic medium: aqueous hydrobromic acid was employed.
Presumably this is a reflection of the increased steric clash
Keywords: Silasultone; Cyclisation; Siloxane; Protodesilylation;
Sulphonation.
*
Corresponding author. Tel.: C44 20 7594 5772; fax: C44 20 7594 5805;
e-mail: c.braddock@imperial.ac.uk
† It seems reasonable to assume that the insertion of SO3 into
silacyclopropanes would yield 5-membered silasultones. To date,
however, this approach has not been demonstrated.
‡ Two isolated examples in the patent literature make reference to the
synthesis of a six-membered silasultone via dehydration of a disulphonic
acid siloxane. Only one example is given in each case, the generality and
scope is not demonstrated, limited experimental details are available and
no characterising spectroscopic data is given. See: Ryan, J. W. (Dow
Corning Corporation, U.S.A.) September 6th, 1966, Patent no.:
CA742243 and Hager, R.; Wolferseder, J.; Deubzer, B. (Wacker-Chemie,
Gmbh) October 24th, 1991, Patent no.: DE4135170.
Scheme 1. Reagents and conditions: (i) 0.02 mmHg, up to 250 8C.
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.05.042

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D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
Scheme 3. Reagents and conditions: (i) Me3SiOSO2Cl, CH2Cl2,
K78/K20 8C, 16 h; (ii) H2O, 20 8C, 1 h.
Scheme 2. Reagents and conditions: (i) aq. HX (XZCl: 13, 15; XZBr 14,
16), reflux 24–36 h; (ii) Proton exchange resin, MeOH, H2O.
between the butyl groups and the phenyl ring in the
Wheland intermediate as the phenyl group undergoes ipso-
protonation. Methylsiloxane 91b was prepared by Dowex-H
mediated acid exchange of disodium disulphonate 17
obtained directly from a sulphonation reaction (vide
infra). Butylsiloxane 101b was most conveniently prepared
by hydrolysis of silasultone 4, which can be obtained
directly by sulphur trioxide insertion1a into butylsilacyclo-
butane 183 using trimethylsilylchlorosulphonate (Scheme 3).
Silasultone 4 formed in this manner is not pure, but
hydrolysis to diacid 10 followed by diethyl ether washes
removes the impurities and subsequent dehydrative cyclisa-
tion delivers pure 4.
t
Scheme 4. Reagents and conditions: (i) NaHSO3, cat. PhCO3 Bu, H2O,
R0OH (R0ZMe: 19; R0ZPr: 20), reflux, 72 h.
(78%). Subsequent free-radical sulphonation using the
original conditions gave the new sulphonate salt 25 in a
pleasing 60% yield. Protodesilylation with aqueous HBr,
followed by treatment with Dowex-H furnished the
disulphonic acid 8 in quantitative yield.
For the longer chain sulphonates 15–17, the sulphonate
groups were introduced by nucleophilic displacement of
chlorides 26–28, respectively, with sodium sulphite
(Scheme 6). Chloride 26 was prepared by the addition of
Negishi’s 1-chloro-4-lithiobutane reagent7 to chlorodi-
methylphenylsilane. Dibutyl chloride 27 was obtained in
good yield (85%) by the reaction of the alkyllithium with
dibutylphenylsilyl triflate 29. The latter was prepared by the
action of triflic acid on dibutyldiphenylsilane8 applying
Matyjaszewski’s method for the preparation of dimethyl-
phenylsilyl triflate.9 Commercially available methoxysilane
28 underwent smooth substitution reaction with sodium
Two distinct methods were employed for the preparation of
phenylsilanes 13–16. Free-radical sulphonation of vinylsi-
lanes 19 and 20 allowed access to silanes 13 and 14. For the
preparation of phenylsilanes 15 and 16, SN2 displacement of
an appropriate alkylchloride with sulphite anion was
employed. Vinyl silanes 19 and 20 were prepared by the
Grignard reactions of phenylmagnesium bromide with
chlorodimethylvinylsilane and double addition of butyl-
magnesium bromide to dichlorophenylvinylsilane,4 respect-
ively. Using a modified method of Weinreb,5 regioselective
free-radical sulphonation of dimethylvinylsilane 19 in a
methanol/water mixture proceeded smoothly to give sodium
sulphonate 13 in good yield (58%) (Scheme 4).§ Under
identical conditions, dibutylvinylsilane 20 failed to undergo
sulphonation and starting material was recovered along with
diphenyltetrabutylsiloxane (from vinyl protodesilylation).
Attempts to perform this sulphonation instead under
microwave conditions or sonication failed. Sulphonation
in an n-propanol/water mixture proceeded to some degree
giving a 15% isolated yield of sodium salt 14. Clearly, the
extra lipophilicity of the dibutyl substrate is problematic
under the aqueous regime required for sodium hydrogen
sulphite solubility. As a solution to this problem, we set
about preparing a water-soluble dibutylvinylsilane substrate
for the sulphonation reaction. We chose to functionalise the
phenyl substituent since it is to be ultimately eliminated
from the substrate during the protodesilylation reaction after
the crucial free-radical sulphonation step. Accordingly,
addition of the Grignard reagent of tertiary amine,
(4-bromobenzyl)dimethylamine (21),6 to dibutylmethoxy-
vinylsilane (22) gave phenylsilane 23 (81%) (Scheme 5).
Quaternisation with methyliodide gave ammonium salt 24
Scheme 5. Reagents and conditions: (i) Mg, THF, reflux, 72 h; (ii) MeI,
EtOH, 20 8C, 48 h; (iii) NaHSO3, cat. PhCO3 Bu, H2O, MeOH, reflux, 72 h;
(iv) aq. HBr, reflux, 32 h; (v) proton exchange resin, MeOH, H2O.
t
§ In an initial approach to the preparation of silasultones, the direct
extrusion of benzene via intramolecular ipso-protodesilylation of the acid
of sodium sulphonate 13 was explored. After much experimentation only
2% of the desired silasutone 1 could be isolated by sublimation.
Scheme 6. Reagents and conditions: (i) Na2SO3.

D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
7235
sulphite in refluxing water to give the disulphonate salt 17
directly (69%). The corresponding reaction of dimethylsi-
lane 26 required the addition of a co-solvent (ethanol) for
reasonable yields (56%). The more lipophilic dibutylsilane
27 gave only poor yields (ca. 14%) under these conditions,
but the application of microwave irradiation (150 8C,
11250 mmHg, 1.5 h) gave the desired product in moderate
yield (42%).
HRMS (EIC) m/z calculated for C3H7O3SiS [MKCH3]C%
150.9885, found 150.9893.
4.2.2.
3,3-Dibutyl-3-sila-1,3-propanesultone
(2).
Following the general procedure, silasultone 2 (97 mg,
0.58 mmol, 67%) was obtained from disulphonic diacid 8
(0.15 g, 0.29 mmol) as a colourless oil: IR (CH2Cl2) nmax
1
1344, 1170, 1082 cmK1; H NMR (270 MHz; CDCl3) d
3.28 (t, 2H, 3JZ7.9 Hz, O3SCH2–), 1.46 (t, 2H, 3JZ7.9 Hz,
O3SCH2CH2–), 1.50–1.18 (m, 8H, alk), 0.96–0.77 (m, 10H,
alk) ppm; 13C NMR (68 MHz; CDCl3) d 47.5 (O3SCH2–),
26.0, 24.3, 13.7, 13.7, 7.7 (O3SCH2CH2–) ppm; 29Si NMR
(99 MHz; CDCl3) d 34.8 ppm; MS (CIC) m/z 268 [MC
NH4]C; HRMS (CIC) m/z calculated for C10H26NO3SiS
[MCNH4]C 268.1403, found 268.1407; MS (EIC) m/z 193
3. Conclusion
In conclusion we have shown that silasultones 1–6 can be
prepared by a dehydrative cyclisation of the corresponding
disulphonic acid siloxanes. In general, the latter compounds
can be approached synthetically by ipso-protodesilylation of
the corresponding phenylsilanes. The phenylsilanes can
either be prepared by free-radical sulphonation of vinylsi-
lanes or sulphite displacement of alkylchlorides as
appropriate. These procedures allow for a general method
for the synthesis of silasultones.
[MKC4H9]C%
;
HRMS (EIC) m/z calculated for
C6H13O3SiS [MKC4H9]C% 193.0355, found 193.0364.
4.2.3. 4,4-Dimethyl-4-sila-1,4-butanesultone (3).
Following the general procedure, silasultone 3 (0.20 g,
1.11 mmol, 65%) was obtained from disulphonic diacid 9
(0.32 g, 0.86 mmol) as a white solid: mp w40–50 8C; IR
(CH2Cl2) nmax 1349, 1257, 1169 cmK1
;
1H NMR
4. Experimental
4.1. General
(270 MHz; CDCl3) d 3.10–3.00 (m, 2H, O3SCH2–), 2.30–
2.15 (m, 2H, –CH2–), 0.85–0.75 (m, 2H, –CH2Si), 0.33 (s,
6H, H3C–Si) ppm; 13C NMR (68 MHz; CDCl3) d 50.7
(O3SCH2–), 19.0 (–CH2–), 11.0 (–CH2Si), K1.0 (H3C–Si)
ppm; 29Si NMR (99 MHz; CDCl3) d 37.9 ppm; MS (CIC)
m/z 198 [MCNH4]C; HRMS (CIC) m/z calculated for
C5H16NO3SiS [MCNH4]C 198.0620, found 198.0617; MS
(EIC) m/z 165 [MKCH3]C%; HRMS (EIC) m/z calculated
for C4H9O3SiS [MKCH3]C% 165.0042, found 165.0044.
Dichlorocyclobutasilane,10 dichlorophenylvinylsilane,4
bromobenzyldimethylamine (21),6 4-chloro-1-iodobutane11
and dibutyldiphenylsilane9 were prepared according to the
published procedures. Trimethylsilylchlorosulfonate was
distilled immediately before use. N0,N0,N,N-Tetramethyl-
ethane-1,2-diamine was dried over NaOH pellets and
distilled immediately before use. DOWEXw50WX4-400
was activated using aqueous hydrochloric acid (1 M) and
washed with water immediately before use. All other
chemicals were used as received.
4.2.4. 4,4-Dibutyl-4-sila-1,4-butanesultone (4).1a,b
Following the general procedure, silasultone 4 (95 mg,
0.36 mmol, 46%) was obtained from disulphonic diacid 10
(0.21 g, 0.39 mmol) as a colourless oil: IR (CH2Cl2) nmax
1
1344, 1172, 1076 cmK1; H NMR (270 MHz; CDCl3) d
All reactions were performed under N2 in dry solvents
unless used in combination with water. Et2O and THF were
distilled from sodium and potassium, respectively, in the
presence of benzophenone. EtOH, used during the synthesis
of ammonium iodide 24, was dried over sodium and
distilled.
3.13–3.05 (m, 2H, O3SCH2–), 2.37–2.23 (m, 2H,
O3SCH2CH2–), 1.50–1.20 (m, 8H, alk), 1.00–0.75 (m,
12H, alk and O3SCH2CH2CH2–) ppm; 13C NMR (68 MHz;
CDCl3) d 50.9 (O3SCH2–), 26.1, 24.3, 19.3 (O3SCH2CH2–),
13.7, 13.5, 8.3 (O3SCH2CH2CH2–) ppm; 29Si NMR
(99 MHz; CDCl3) d 36.1 ppm; MS (CIC) m/z 282 [MC
NH4]C; HRMS (CIC) m/z calculated for C11H28NO3SiS
[MCNH4]C 282.1559, found 282.1559; MS (EIC) m/z 207
4.2. General procedure for silasultone formation
[MKC4H9]C%
;
HRMS (EIC) m/z calculated for
Disulphonic siloxane was placed in a sublimation apparatus
under reduced pressure (0.02 mmHg) and gradually heated
to 250 8C. The sublimed product was collected under N2.
C7H15O3SiS [MKC4H9]C% 207.0511, found 207.0518.
Alternative synthesis of silasultone 4: to neat silacyclo-
butane 18 (2.0 g, 7.56 mmol) at K20 8C, trimethylsilyl-
chlorosulfonate (1.17 mL, 7.56 mmol) was added dropwise
over 10 min. The light orange mixture was allowed to warm
to room temperature, stirred for 6 h at room temperature and
the volatiles were removed under reduced pressure
(0.02 mmHg) at 60–80 8C for 30 min to leave silasultone
4 (2.0 g, 7.56 mmol, 100%) as a colourless oil: data as
reported above.
4.2.1. 3,3-Dimethyl-3-sila-1,3-propanesultone (1).
Following the general procedure, silasultone 1 (0.11 g,
0.69 mmol, 67%) was obtained from disulphonic diacid 7
(0.18 g, 0.51 mmol) as a white solid: mp 95–105 8C; IR
(CH2Cl2) nmax 1344, 1257, 1172, 1070 cmK1 1H NMR
;
(270 MHz; CDCl3) d 3.35–3.27 (m, 2H, –CH2CH2Si), 1.53–
1.44 (m, 2H, –CH2Si), 0.51 (s, 6H, H3C–Si) ppm; 13C NMR
(68 MHz; CDCl3) d 47.4 (–CH2CH2Si), 11.8 (–CH2Si),
K0.1 (H3C–Si) ppm; 29Si NMR (99 MHz; CDCl3) d
32.9 ppm; MS (CIC) m/z 184 [MCNH4]C; HRMS (CIC)
m/z calculated for C4H14NO3SiS [MCNH4]C 184.0464,
4.2.5. 5,5-Dimethyl-5-sila-1,5-pentanesultone (5).
Following the general method, silasultone 5 (80 mg,
0.41 mmol, 48%) was obtained from disulphonic diacid 11
(0.18 g, 0.43 mmol) as a colourless oil: IR (CH2Cl2) nmax
1351, 1257, 1171, 1070 cmK1; 1H NMR (270 MHz; CDCl3)
found 184.0466; MS (EIC) m/z 151 [MKCH3]C%
;

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D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
d 3.28–3.18 (m, 2H, O3SCH2–), 2.05–1.91 (m, 2H,
O3SCH2CH2–), 1.88–1.76 (m, 2H, –CH2CH2Si), 1.11–
1.00 (m, 2H, –CH2Si), 0.33 (s, 6H, H3C–Si) ppm; 13C
NMR (68 MHz; CDCl3) d 53.6 (O3SCH2–), 26.0
(O3SCH2CH2–), 21.6 (–CH2CH2Si), 16.7 (–CH2Si), K1.2
(CH3Si) ppm; 29Si NMR (99 MHz; CDCl3) d 29.7 ppm; MS
(CIC) m/z 212 [MCNH4]C; HRMS (CIC) m/z calculated
for C6H14NO3SiS [MCNH4]C 212.0777, found 212.0783;
MS (EIC) m/z 179 [MKCH3]C; HRMS (EIC) m/z
calculated for C5H11O3SiS [MKCH3]C 179.0198, found
179.0206.
(68 MHz; DMSO-d61) d 46.7 (HO3SCH2–), 13.5 (–CH2Si),
0.7 (H3C–Si) ppm; H NMR (270 MHz; CDCl3) d 3.16–
3.02 (m, 4H), 1.13–1.02 (m, 4H), 0.13 (s, 12H) ppm; MS
(CIC) m/z 350 [MKH2OCNH4]C; HRMS (CIC) m/z
calculated for C8H24NO6Si2S2 [MKH2OCNH4]C
350.0584, found 350.0579.
4.3.2. 3,3,5,5-Tetrabutyl-4-oxa-3,5-disilaheptane-1,7-dis-
ulphonic diacid (8). Following the general procedure above
(Part A and Part B) using sodium sulphonate 14 (0.46 g,
1.31 mmol) or {2-[dibutyl-(p-trimethylammoniumiodide)-
benzyl]-silyl}ethane sulfonate (25) (0.72 g, 1.31 mmol)
gave disulphonic diacid 8 (0.34 g, 0.66 mmol, 100%) as a
4.2.6.
5,5-Dibutyl-5-sila-1,5-pentanesultone
(6).
1
Following the general method, silasultone 6 (52 mg,
0.19 mmol, 45%) was obtained from disulphonic diacid 12
(0.12 g, 0.21 mmol) as a colourless oil: IR (CH2Cl2) nmax
1376, 1160 cmK1; 1H NMR (270 MHz; CDCl3) d 3.27–3.17
(m, 2H, O3SCH2–), 2.04–1.90 (m, 2H, O3SCH2CH2–),
1.90–1.75 (m, 2H, O3SCH2CH2CH2–), 1.44–1.26 (m, 8H,
alk), 1.08–0.97 (m, 2H, O3SCH2CH2CH2CH2–), 0.93–0.69
(m, 10H, alk) ppm; 13C NMR (68 MHz; CDCl3) d 53.7
(O3SCH2–), 26.3, 26.0 (O3SCH2CH2–), 24.7, 22.1 (O3
SCH2CH2CH2–), 14.2 (O3SCH2CH2CH2CH2–), 13.7,
13.6 ppm; 29Si NMR (99 MHz; CDCl3) d 27.7 ppm; MS
(CIC) m/z 296 [MCNH4]C; HRMS (CIC) m/z calculated
for C12H30NO3SiS [MCNH4]C 296.1716, found 296.1705;
MS (EIC) m/z 221 [MKC4H9]C%; HRMS (EIC) m/z
calculated for C8H17O3SiS [MKC4H9]C% 221.0668, found
221.0677.
pale yellow oil: H NMR (270 MHz; DMSO-d6) d 2.61–
2.38 (m, 4H, HO3SCH2–), 1.35–1.17 (m, 16H, alk), 0.93–
0.75 (m, 16H, alk and HO3SCH2CH2–), 0.61–0.41 (m, 8H,
alk) ppm; 13C NMR (68 MHz; DMSO-d6) d 46.7
(HO3SCH2–), 26.4, 25.4, 15.1, 14.1, 11.0 (HO3SCH2CH2–)
1
ppm; H NMR (270 MHz; CDCl3) d 2.96–2.75 (m, 4H),
1.45–1.16 (m, 16H), 1.09–0.92 (m, 4H), 0.92–0.76 (m,
12H), 0.66–0.45 (m, 8H) ppm; MS (CIC) m/z 518 [MK
H2OCNH4]C; HRMS (CIC) m/z calculated for C20H48-
NO6Si2S2 [MKH2OCNH4]C 518.2462, found 518.2462.
4.3.3. 4,4,6,6-Tetramethyl-5-oxa-4,6-disilanonane-1,9-
disulphonic diacid (9).1b Following the general procedure
above (Part B only) using disodium disulfonate 17 (1.54 g,
3.64 mmol), gave disulphonic diacid 9 (1.38 g, 3.64 mmol,
100%) as a pale yellow oil: 1H NMR (270 MHz; DMSO-d6)
3
d 2.69 (br t, 4H, JZ7.6 Hz, HO3SCH2–), 1.70–1.55 (m,
3
4H, –CH2–), 0.55 (br t, 4H, JZ8.5 Hz, –CH2Si), 0.01 (s,
4.3. General procedure for the formation of disulphonic
acids
12H, H3C–Si) ppm; 13C NMR (68 MHz; DMSO-d6) d 54.9
(HO3SCH2–), 19.0 (–CH2–), 17.4 (–CH2Si), 0.8 (H3C–Si)
ppm; H NMR (270 MHz; CDCl3) d 3.08–2.88 (m, 4H),
1
(A) A solution of arylsilane (1/50, w/v) in an aqueous
solution of HCl (12 M) (13, 15) or HBr (12 M) (14, 16) was
heated at reflux. After 24 h (13, 15) or 32 h (14, 16) the
mixture was allowed to cool to room temperature and
concentrated. The resulting di-sodium salts were extracted
with PrOH and the resultant liquor was concentrated
to dryness. (B) A solution of the sodium salt (typically
w10% w/v) in MeOH:H2O (1:1) was passed through a
DOWEXw50WX4-400 proton exchange resin packed
column (typically w100 times as much mass of wet resin
as sodium salt) at room temperature. The column was eluted
further with MeOH:H2O (1:1) (typically w10 times as
much volume as sodium salt solution) and H2O (typically
w10 times as much volume as sodium salt solution). The
eluate was concentrated to afford quantitatively the expected
acid as a pale yellow oil. Chemical shifts of the protons from
the sulphonic acid groups are not reported since they range
variously and unpredictably between 13 and 7 ppm
irrespective of the solvent or the sulphonic acid. These
compounds also displayed two very broad, intense
absorbances in their IR spectra at 3600–2500 and 2000–
1500 wavenumbers.
1.83–1.65 (m, 4H), 0.60–0.46 (m, 4H), K0.04 (s, 12H); MS
(CIC) m/z 378 [MKH2OCNH4]C; HRMS (CIC) m/z
calculated for C10H28O6Si2S2 [MKH2OCNH4]C
378.0897 found 378.0899.
4.3.4. 4,4,6,6-Tetrabutyl-5-oxa-4,6-disilanonane-1,9-dis-
ulphonic diacid (10).1b To silasultone 4 (2.0 g, 7.56 mmol)
at room temperature was added H2O (10 mL). The resulting
solution was stirred for 1 h, and washed with Et2O (3!
10 mL). The resulting mixture was dissolved in MeOH and
concentrated to give disulphonic diacid 10 (2.1 g,
1
3.78 mmol, 100%) as an orange oil: H NMR (270 MHz;
DMSO-d6) d 2.66 (br t, 4H, 3JZ7.6 Hz, HO3SCH2–), 1.73–
1.54 (m, 4H, HO3SCH2CH2–), 1.37–1.16 (m, 20H, alk and
HO3SCH2CH2CH2–), 0.94–0.78 (m, 12H, alk), 0.65–0.40
(m, 8H, alk) ppm; 13C NMR (68 MHz; DMSO-d6) d 55.3
(HO3SCH2–), 26.6, 25.4, 19.0 (HO3SCH2CH2–), 15.4, 15.1
(HO3SCH2CH2CH2–), 14.1(H3C–) ppm; 1H NMR
(270 MHz; CDCl3) d 3.01–2.83 (m, 4H), 1.91–1.66 (m,
4H), 1.52–1.18 (m, 20H), 1.02–0.71 (m, 12H), 0.70–0.45
(m, 8H) ppm; MS (CIC) m/z 546 [MKH2OCNH4]C, 281
[MKC11H25O4SSi]C; HRMS (CIC) m/z calculated for
C22H52O6NSi2S2 [MKH2OCNH4]C 546.2775, found
546.2780.
4.3.1. 3,3,5,5-Tetramethyl-4-oxa-3,5-disilaheptane-1,7-
disulphonic diacid (7). Following the general procedure
above (Part A and Part B) using sodium sulphonate 13
(1.23 g, 4.62 mmol) gave disulphonic diacid 7 (0.84 g,
2.22 mmol, 96%) as a pale yellow oil: 1H NMR (270 MHz;
DMSO-d6) d 2.65–2.53 (m, 4H, HO3SCH2–), 0.93–0.80 (m,
4H, –CH2Si), 0.03 (s, 12H, H3C–Si) ppm; 13C NMR
4.3.5. 5,5,7,7-Tetramethyl-6-oxa-5,7-disilaundecane-
1,11-disulphonic diacid (11). Following the general
procedure above (Part A and Part B) using sodium
sulphonate 15 (1.21 g, 4.11 mmol) gave disulphonic diacid

D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
7237
11 (0.84 g, 2.05 mmol, 100%) as a pale yellow oil: 1H NMR
(270 MHz; DMSO-d6) d 2.60–2.45 (m, 4H, HO3SCH2–),
1.71–1.49 (m, 4H, HO3SCH2CH2–), 1.38–1.24 (m, 4H,
–CH2CH2Si), 0.56–0.36 (m, 4H, –CH2Si), 0.00 (s, 12H,
H3C–Si) ppm; 13C NMR (68 MHz; DMSO-d6) d 51.9
(HO3SCH2–), 28.8 (HO3SCH2CH2–), 22.8 (–CH2CH2Si),
1 (0.27 g, 1.6 mmol, 2%) was collected as a white solid.
Data as reported above.
4.3.8. Sodium 2-(dibutylphenylsilyl)ethanesulfonate (14).
An aqueous solution of HCl (20 mL, 12 M, 244 mmol), a
solution of vinylsilane 20 (20 g, 81 mmol) in PrOH (50 mL)
followed by t-butyl benzoic peroxide (1.5 mL, 8 mmol)
were added dropwise to a solution of Na2SO3 (31 g,
244 mmol) in H2O (24 mL) over 10 min. The resulting
biphasic suspension was heated at reflux. After 120 h, the
mixture was allowed to cool to room temperature, washed
with Et2O (3!40 mL), and concentrated to dryness. The
resulting salts were extracted with PrOH (5!10 mL) and
the resultant liquor was concentrated to dryness to afford
sodium sulfonate 14 (4.3 g, 12.2 mmol, 15%) as a white
1
18.4 (–CH2Si), 1.0 (H3C–Si) ppm; H NMR (270 MHz;
CDCl3) d 3.02–2.88 (m, 4H), 1.85–1.70 (m, 4H), 1.54–1.33
(m, 4H), 0.55–0.45 (m, 4H), 0.03 (s, 12H) ppm; MS (CIC)
m/z 406 [MKH2OCNH4]C; HRMS (CIC) m/z calculated
for C12H32NO6Si2S2 [MKH2OCNH4]C 406.1210, found
406.1201.
4.3.6. 5,5,7,7-Tetrabutyl-6-oxa-5,7-disilaundecane-1,11-
disulphonic diacid (12). Following the general procedure
above (Part A and Part B) using sodium sulphonate 16
(0.16 g, 0.42 mmol) gave disulphonic diacid 12 (0.12 g,
0.21 mmol, 100%) as a pale yellow oil: 1H NMR (270 MHz;
DMSO-d6) d 2.62–2.50 (m, 4H, HO3SCH2–), 1.68–1.55
(m, 4H, HO3SCH2CH2–), 1.48–1.12 (m, 20H, alk and
HO3SCH2CH2CH2–), 0.98–0.72 (m, 12H, alk), 0.63–0.35
(m, 12H, alk and HO3SCH2CH2CH2CH2–) ppm; 13C NMR
(68 MHz; DMSO-d6) d 51.7 (HO3SCH2–), 29.0 (HO3SCH2
CH2–), 26.6, 25.6, 22.6 (HO3SCH2CH2CH2–), 15.7 (HO3
SCH2CH2CH2CH2–), 15.4, 14.2 (H3C–) ppm; 1H NMR
(270 MHz; CDCl3) d 3.02–2.88 (m, 4H), 1.89–1.60 (m, 4H),
1.58–1.11 (m, 20H), 0.98–0.71 (m, 12H), 0.67–0.35 (m,
12H) ppm; MS (CIC) m/z 574 [MKH2OCNH4]C; HRMS
(CIC) m/z calculated for C24H56NO6Si2S2 [MKH2OC
NH4]C 574.3088, found 574.3090.
solid: mp 280 8C (decomp.); IR (DRIFTS) nmax 1190 cmK1
;
1H NMR (270 MHz; DMSO-d6) d 7.49–7.41 (m, 2H, Ar),
7.41–7.31 (m, 3H, Ar), 2.42–2.28 (m, 2H, NaO3SCH2–),
1.35–1.18 (m, 8H, alk), 1.18–1.06 (m, 2H, NaO3SCH2CH2–),
0.91–0.69 (m, 10H, alk) ppm; 13C NMR (68 MHz; DMSO-
d6) d 137.3, 134.5, 129.7, 128.5, 47.0 (NaO3SCH2–), 26.8,
26.3, 14.3 (H3C–), 12.2, 8.5 (NaO3SCH2CH2–) ppm; MS
(FABK) m/z 327 [MKNa]K.
4.3.9. Sodium 4-(dimethylphenylsilanyl)butane-1-sulfo-
nate (15). A vigorously stirred biphasic suspension of
Na2SO3 (6.6 g, 44.9 mmol), chlorobutylsilane 26 (2.4 g,
10.5 mmol) and NaI (0.8 g, 5.2 mmol) in H2O (25 mL) and
EtOH (15 mL) was heated at reflux. After 72 h, the mixture
was allowed to cool to room temperature, extracted with
Et2O (3!30 mL) and the aqueous was concentrated to
dryness. The resulting salts were extracted with EtOH (5!
30 mL) and the resultant liquor was concentrated. The
resulting salts were washed with acetone (3!10 mL) and
dried under vacuum to afford sodium sulfonate 15 (1.6 g,
5.9 mmol, 56%) as a white solid: mp 186–190 8C
4.3.7. Sodium 2-(dimethylphenylsilyl)ethanesulfonate
(13). An aqueous solution of HCl (3.3 mL, 12 M,
40 mmol) and then a solution of vinylsilane 19 (3.6 mL,
20 mmol) in MeOH (8 mL) followed by t-butylbenzoic
peroxide (0.25 mL, 1.3 mmol) were added dropwise to a
solution of Na2SO3 (5.0 g, 40 mmol) in H2O (4 mL) over
10 min. The resulting biphasic suspension was heated at
reflux. After 72 h, the mixture was allowed to cool to room
temperature, washed with Et2O (3!15 mL), and concen-
trated to dryness. The resulting salts were extracted with
EtOH (5!20 mL) and the resultant liquor was concentrated
to dryness to afford sodium sulfonate 13 (3.1 g, 11.6 mmol,
58%) as a white solid: mp 185–187 8C (decomp.); IR
(DRIFTS) nmax 1191 cmK1; 1H NMR (270 MHz; DMSO-d6)
d 7.56–7.42 (m, 2H, Ar), 7.42–7.30 (m, 3H, Ar), 2.42–2.30 (m,
2H, NaO3SCH2–), 1.13–1.02 (m, 2H, –CH2Si), 0.23 (s, 6H,
H3C–Si) ppm; 13C NMR (68 MHz; DMSO-d6) d 138.8,
133.9, 129.6, 128.4, 40.9 (NaO3SCH2–), 11.6 (–CH2Si),
K2.7 (H3C–Si) ppm; MS (FABK) m/z 243 [MKNa]K.
Sodium salt 13 could be converted to the corresponding
monosulphonic acid (a yellow oil) using Part B of the
general procedure above: 1H NMR (270 MHz; DMSO-d6) d
7.53–7.42 (m, 2H, Ar), 7.40–7.29 (m, 3H, Ar), 2.93–2.78
(m, 2H, HO3SCH2–), 1.34–1.09 (m, 2H, –CH2Si), 0.27 (s,
6H, H3C–Si) ppm; 13C NMR (68 MHz; DMSO-d6) d 138.4,
133.9, 129.7, 128.4, 47.3 (HO3SCH2–), 11.1 (–CH2Si),
K2.8 ppm (H3C–Si); MS (CIC) m/z 184 [MKC6H6C
NH4]C. ipso-Desilylation–cyclisation was attempted: the
sulphonic acid (22 g, 90 mmol) was heated to 250 8C in a
short-path distillation apparatus under high vacuum
(w0.02 mmHg) for 72 h and then allowed to cool to room
temperature. From the receiving flask under N2, silasultone
(decomp.); IR (DRIFTS) nmax 1193 cmK1 1H NMR
;
(270 MHz; DMSO-d6) d 7.54–7.41 (m, 2H, Ar), 7.41–7.28
(m, 3H, Ar), 2.48–2.35 (m, 2H, NaO3SCH2–), 1.68–1.49 (m,
2H, NaO3SCH2CH2–), 1.38–1.20 (m, 2H, –CH2CH2Si),
0.76–0.61 (m, 2H, –CH2Si), 0.22 (s, 6H, H3C–Si) ppm; 13
C
NMR (68 MHz; DMSO-d6) d 139.4, 133.9, 129.4, 128.3,
51.7 (NaO3SCH2–), 29.4 (NaO3SCH2CH2–), 23.5 (–CH2-
CH2Si), 15.6 (–CH2Si), K2.4 (H3C–Si) ppm; MS (FABK)
m/z 271 [MKNa]K.
4.3.10. Sodium 4-(dibutylphenylsilanyl)butane-1-sulfo-
nate (16). A biphasic suspension of Na2SO3 (0.7 g,
5.6 mmol), (4-chlorobutyl)silane 27 (0.32 g, 1 mmol) in
H2O (1.5 mL) and EtOH (1.5 mL) was heated at 150 8C at
11,250 mmHg for 60 min using a microwave reactor. After
cooling, the biphasic suspension was washed with Et2O
(3!5 mL) and the aqueous layer was concentrated to
dryness. The resulting salts were extracted with EtOH (3!
10 mL) and PrOH (3!10 mL) and the resultant combined
liquors were concentrated to dryness to afford sodium
sulfonate 16 (0.16 g, 0.42 mmol, 42%) as a white solid: mp
1
240–245 8C (decomp); IR (DRIFTS) nmax 1190 cmK1; H
NMR (270 MHz; DMSO-d6) d 7.48–7.39 (m, 2H, Ar), 7.37–
7.27 (m, 3H, Ar), 2.52–2.39 (m, 2H, NaO3SCH2–), 1.71–
1.53 (m, 2H, NaO3SCH2CH2–), 1.39–1.12 (m, 10H, alk and
NaO3SCH2CH2CH2–), 0.90–0.65 (m, 12H, alk and NaO3-
SCH2CH2CH2CH2–) ppm; 13C NMR (68 MHz; DMSO-d6)

7238
D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
d 137.8, 134.4, 129.5, 128.4, 51.9 (NaO3SCH2–), 29.7
(NaO3SCH2CH2–), 26.8, 26.3, 23.6 (NaO3SCH2CH2CH2–),
14.3 (H3C–), 12.6 (NaO3SCH2CH2CH2CH2–), 12.3 ppm;
MS (FABK) m/z 355 [MKNa]K.
were separated and the aqueous layer was extracted with
Et2O (3!20 mL). The organics were combined, dried over
MgSO4, concentrated and distilled under reduced pressure
to give silane 19 (6.1 g, 2.3 mmol, 75%) as a colourless oil:
bp 90–93 8C/40 mmHg (lit.12 82 8C/20 mmHg); IR (neat)
nmax 1592, 1249 cmK1 1H NMR (270 MHz; CDCl3) d
;
4.3.11. Disodium 4,4,6,6-tetramethyl-5-oxa-4,6-disilano-
nane-1,9-disulfonate (17). A vigorously stirred biphasic
suspension of Na2SO3 (25.2 g, 200 mmol), (3-chloropro-
pyl)methoxydimethylsilane 28 (6.68 g, 40.0 mmol) in H2O
(135 mL) was heated at reflux. After 96 h, the mixture was
allowed to cool to room temperature, extracted with Et2O
(3!100 mL) and the aqueous was concentrated to dryness
under vacuum. The resulting salts were extracted with EtOH
(5!100 mL) and the resultant liquor was concentrated to
dryness under vacuum to afford disodium disulfonate 17
(5.83 g, 13.8 mmol, 69%) as a white solid: mpO350 8C; IR
7.68–7.55 (m, 2H, Ar), 7.50–7.37 (m, 3H, Ar), 6.60 (dd, 1H,
3JZ14.5, 20.0 Hz, Si–CH]CHcisHtrans), 6.13 (dd, 1H, 2JZ
3
3.9 Hz, JZ14.5 Hz, Si–CH]CHcisHtrans), 5.83 (dd, 1H,
2JZ3.9 Hz, 3JZ20.0 Hz, Si–CH]CHcisHtrans), 0.43 (s, 6H,
H3C–Si) ppm; 13C NMR (68 MHz; CDCl3) d 138.6, 138.1,
134.0, 133.0, 129.1, 127.9, K2.8 (H3C–Si) ppm; H NMR
1
(270 MHz; DMSO-d6) d 7.54–7.47 (m, 2H), 7.38–7.31 (m,
3
2
3H), 6.29 (dd, 1H, JZ14.5, 20.0 Hz), 6.04 (dd, 1H, JZ
3.9 Hz, 3JZ14.5 Hz), 5.74 (dd, 1H, 2JZ3.9 Hz, 3JZ
20.0 Hz), 0.32 (s, 6H); 13C NMR (68 MHz; DMSO-d6) d
138.4, 138.2, 134.1, 133.4, 129.6, 128.3, -2.5 ppm; MS
(CIC) m/z 180 [MCNH4]C, 163 [MCH]C.
(DRIFTS) nmax 1213, 1184 cmK1 1H NMR (270 MHz;
;
D2O) d 3.11–2.96 (m, 4H, NaO3SCH2–), 2.00–1.84 (m, 4H,
–CH2–), 0.88–0.74 (m, 4H, –CH2Si), 0.26 (s, 12H, H3C–Si)
ppm; 13C NMR (68 MHz; D2O) d 54.4 (NaO3SCH2–), 18.6
4.3.14. Dibutylphenylvinylsilane (20). To a stirred suspen-
sion of Mg (7.3 g, 300 mmol) in Et2O (60 mL) at room
temperature, a solution of 4-bromobutane (16.1 mL,
150 mmol) in Et2O (16 mL) was added dropwise over
1.5 h to maintain a gentle reflux. After a further 3 h at room
temperature, the solution of Grignard reagent was decanted
from the remaining Mg and added dropwise over 30 min to
a solution of dichlorophenylvinylsilane4 (10.2 mL,
50 mmol) in Et2O (20 mL) at room temperature. After
48 h at room temperature, a saturated aqueous NH4Cl
solution (100 mL) was added. The layers were separated,
and the aqueous layer was extracted with Et2O (3!
100 mL). The organics were combined, dried over
MgSO4, concentrated and the residual oil was distilled
under vacuum to afford silane 20 (10.5 g, 42 mmol, 85%) as
a colourless oil: bp 120–125 8C/4 mmHg; IR (neat) nmax
1
(–CH2–), 16.3 (–CH2Si), K1.00 (H3C–Si) ppm; H NMR
(270 MHz; DMSO-d6) d 2.47–2.41 (m, 4H), 1.70–1.55 (m,
4H), 0.51–0.44 (m, 4H), K0.02 (s, 12H) ppm; 13C NMR
(68 MHz; DMSO-d6) d 55.4, 19.5, 18.0, 1.0 ppm; MS
(FABK) m/z 399 [MKNa]K, 319 [MKSO3Na]K.
4.3.12. Dibutylsilacyclobutane (18).3 To a stirred suspen-
sion of Mg (1.54 g, 63.3 mmol) in Et2O (20 mL) at room
temperature was added dropwise
a
solution of
4-bromobutane (6.8 mL, 63.3 mmol) in Et2O (10 mL) over
30 min so as to maintain a gentle reflux. After a further 3 h
at room temperature, the solution of Grignard reagent was
decanted from the remaining Mg and added dropwise to a
solution of dichlorocyclobutasilane10 (2.5 mL, 21.1 mmol)
in Et2O (18 mL) at room temperature over 30 min. The
resulting mixture was stirred at room temperature for 48 h,
aqueous NH4Cl solution (40 mL) was added, the layers were
separated and the aqueous layer was extracted with Et2O
(3!40 mL). The combined organics were dried over
MgSO4, concentrated and distilled under reduced pressure
to afford silane 18 (3.4 g, 18.3 mmol, 87%) as a colourless
oil: bp 104–108 8C/4 mmHg (lit.1e 63 8C/0.3 mmHg); IR
1
1593 cmK1; H NMR (270 MHz; CDCl3) d 7.75–7.51 (m,
3
2H, Ar), 7.51–7.35 (m, 3H, Ar), 6.37 (dd, 1H, JZ14.8,
2
19.9 Hz, Si–CH]CHcisHtrans), 6.19 (dd, 1H, JZ4.4 Hz,
3JZ14.8 Hz, Si–CH]CHcisHtrans), 5.83 (dd, 1H, 2JZ
3
4.4 Hz, JZ19.9 Hz, Si–CH]CHcisHtrans), 1.53–1.28 (m,
8H, alk), 1.10–0.81 (m, 10H, alk) ppm; 13C NMR (68 MHz;
CDCl3) d 136.0, 134.4, 133.7, 133.7, 128.9, 127.7, 26.7,
26.0, 13.7 (H3C–), 12.2 ppm; MS (EIC) m/z 246 [M]C%, 189
[MKC4H9]C%; HRMS (EIC) m/z calculated for C16H26Si
[M]C% 246.1804, found 246.1792.
(neat) nmax 2929, 2872, 2858, 2798 cmK1 1H NMR
;
(270 MHz; CDCl3) d 2.05 (quintuplet, 2H, 3JZ8.3 Hz,
Si(CH2)2CH2), 1.50–1.22 (m, 8H, –CH2CH2CH3), 0.95 (t,
3
4H, JZ8.3 Hz, Si(CH2)2CH2), 0.90 (t, 6H, 3JZ6.9 Hz,
–CH3), 0.80–0.61 (m, 4H, –CH2CH2CH2CH3) ppm; 13C
NMR (68 MHz; CDCl3) d 26.5, 26.1, 18.5 (Si(CH2)2CH2),
14.9 (Si(CH2)2CH2), 13.9 (–CH3), 12.2 ppm; MS (CIC) m/z
202 [MCNH4]C.
4.3.15. Dibutylmethoxyvinylsilane (22). To a stirred
suspension of Mg (5.8 g, 240 mmol) in Et2O (50 mL) at
room temperature, a solution of 4-bromobutane (19.8 mL,
184 mmol) in Et2O (25 mL) was added dropwise over 1.5 h.
After a further 3 h at room temperature, the solution of
Grignard reagent was decanted from the remaining Mg and
added dropwise over 30 min to a solution of trimethoxy-
vinylsilane (12.2 mL, 80 mmol) in Et2O (20 mL) at room
temperature. The resulting beige suspension was stirred for
a further 18 h at room temperature. The salts were filtered
off and washed with petroleum ether (3!20 mL), the filtrate
concentrated, petroleum ether (60 mL) was added and the
resulting salts were filtered off and washed repeatedly with
petroleum ether (3!20 mL). The combined filtrates were
concentrated and distilled under reduced pressure to afford
methoxysilane 22 (2.5 g, 12.2 mmol, 72%) as a colourless
4.3.13. Dimethylphenylvinylsilane (19). To a suspension
of Mg (4.0 g, 165 mmol) and a crystal of iodine in Et2O
(20 mL) at room temperature, bromobenzene (1.2 mL,
11.5 mmol) was added dropwise over 20 min until
decolouration was observed. The remaining bromobenzene
(4.6 mL, 43.5 mmol) was added dropwise over 1 h to
maintain a gentle reflux. After a further 1 h at room
temperature, the solution of Grignard reagent was decanted
from the remaining Mg and added dropwise over 1 h to a
solution of chlorodimethylvinylsilane (7.1 mL, 50 mmol) in
Et2O (40 mL) at room temperature. After a further 16 h,
aqueous NH4Cl solution (40 mL) was added. The layers
1
oil: bp 80–82 8C/4 mmHg; IR (neat) nmax 1593 cmK1; H

D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
7239
NMR (270 MHz; CDCl3) d 6.06 (m, 1H), 6.04 (m, 1H), 5.77
(m, 1H), 3.44 (s, 3H, H3C–O), 1.41–1.20 (m, 8H, alk), 0.96–
0.76 (m, 6H, alk), 0.76–0.58 (m, 4H, alk) ppm; 13C NMR
(68 MHz; CDCl3) d 135.3, 133.9, 50.8 (H3C–O), 26.5, 25.2,
13.8, 12.8 ppm; MS (CIC) m/z 218 [MCNH4]C, 201 [MC
H]C, 186 [MKMeOHCNH4]C; HRMS (CIC) m/z calcu-
lated for C11H28NOSi [MCNH4]C 218.1940, found
218.1942.
5 min followed by t-butylbenzoic peroxide (250 mL,
0.4 mmol). The resulting mixture was heated at reflux.
After 72 h, the mixture was allowed to cool to room
temperature, washed with Et2O, and concentrated to
dryness. The resulting salts were extracted with EtOH
(5!20 mL) and the resultant liquor was concentrated to
dryness to afford sodium sulfonate 25 (4.8 g, 8.9 mmol,
60%) as a white solid: mp O350 8C; IR (DRIFTS) ymax
1
1193 cmK1; H NMR (270 MHz; DMSO-d6) d 7.72–7.50
(m, 4H, Ar), 4.56 (s, 2H, ArCH2–), 3.03 (s, 9H,
–NC(CH3)3), 2.43–2.30 (m, 2H, NaO3SCH2–), 1.41–1.21
(m, 8H, alk), 1.22–1.13 (m, 2H, NaO3SCH2CH2–), 0.93–
0.69 (m, 10H, alk) ppm; 13C NMR (68 MHz; DMSO-d6) d
139.9, 134.8, 132.7, 129.4, 68.1 (ArCH2–), 52.4
(–NC(CH3)3), 46.8 (NaO3SCH2–), 26.5, 26.0, 14.1
(H3CCH2–), 11.8, 8.1 (NaO3SCH2CH2–) ppm; MS
(FABC) m/z 422 [MKI]C; HRMS (FABC) m/z calculated
for C20H37NO3NaSiS [MKI]C 422.2179, found 422.2161.
4.3.16. [4-(Dibutylvinylsilyl)benzyl]dimethylamine (23).
To a suspension of Mg (2.3 g, 96.0 mmol) in THF (60 mL)
under reflux, (4-bromobenzyl)dimethylamine (21)6 (10.3 g,
48.0 mmol) was added dropwise over 2 h. After a further
30 min under reflux, methoxysilane 22 (4.8 g, 24.0 mmol)
was added dropwise over 1 h. After a further 72 h at reflux,
the reaction mixture was allowed to cool to room
temperature and saturated aqueous NH4Cl solution
(60 mL) was added. The layers were separated and the
aqueous layer was extracted with Et2O (3!60 mL). The
organics were combined, dried over MgSO4, concentrated,
and the volatiles were removed under reduced pressure
(4 mmHg) to leave amine 23 (5.9 g, 19.4 mmol, 81%) as a
yellow oil: IR (neat) nma3x 1601 cmK1; 1H NMR (270 MHz;
4.3.19. Dimethyl(4-chlorobutyl)phenylsilane (26). To a
solution of t-BuLi (39.5 mL, 1.55 M in pentane, 60.8 mmol)
in Et2O (20 mL) at K78 8C, 1-chloro-4-iodobutane11
(3.8 mL, 30.4 mmol) was added dropwise over 5 min, and
the solution was stirred for a further 1 h. A solution of
chlorodimethylphenylsilane (4.2 mL, 25.3 mmol) in Et2O
(20 mL) was added dropwise over a 10 min period. The
resulting solution was allowed to warm to room temperature
and stirred for 16 h. Aqueous NH4Cl solution (40 mL) was
added and the layers were separated. The aqueous layer was
extracted with Et2O (3!40 mL) and the combined organics
were washed with brine (60 mL), dried over MgSO4,
concentrated and distilled to afford (4-chlorobutyl)silane
26 (4.9 g, 21.5 mmol, 85%) as a colourless oil: bp 138–
140 8C/4 mmHg (lit.13 bp 87–89 8C/1 mmHg); 1H NMR
(270 MHz; CDCl3) d 7.63–7.47 (m, 2H, Ar), 7.46–7.32 (m,
3H, Ar), 3.54 (t, 2H, 3JZ6.7 Hz, ClCH2–), 1.81 (quintuplet,
3
CDCl3) d 7.47 (d, 2H, JZ6.8 Hz, Ar), 7.27 (d, 2H, JZ
6.8 Hz, Ar), 6.27 (dd, 1H, 3JZ10.6, 19.8 Hz, Si–
2
3
CH]CHcisHtrans), 6.12 (dd, 1H, JZ4.3 Hz, JZ10.6 Hz,
Si–CH]CHcisHtrans), 5.76 (dd, 1H, 2JZ4.3 Hz, 3JZ
19.8 Hz, Si–CH]CHcisHtrans), 3.41 (s, 2H, ArCH2–), 2.22
(s, 6H, –N(CH3)2), 1.42–1.20 (m, 8H, alk), 0.95–0.78 (m,
10H, alk) ppm; 13C NMR (68 MHz; CDCl3) d 139.5, 136.2,
135.3, 134.5, 133.7, 128.6, 64.5 (ArCH2–), 45.5
(–N(CH3)2), 26.7, 26.0, 13.8, 12.3 ppm; MS (CIC) m/z
304 [MCH]C; HRMS (CIC) m/z calculated for C19H34NSi
[MCH]C 304.2461, found 304.2470.
4.3.17. [4-(Dibutylvinylsilyl)benzyl]trimethylammonium
iodide (24). To a solution of amine 23 (5.8 g, 19.1 mmol) in
EtOH (40 mL) at 0 8C, MeI (1.3 mL, 20.0 mmol) was added
dropwise over 30 min. The solution was allowed to warm to
room temperature and stirred for 48 h. To the resulting
mixture was added Et2O (60 mL) and the precipitate
obtained was filtered off and washed with Et2O (2!
30 mL). The residue was dried under vacuum for 4 h to give
ammonium iodide 24 (6.7 g, 15.0 mmol, 78%) as a white
solid: mp 195–196 8C (decomp.); IR (DRIFTS) nmax
3
2H, JZ6.7 Hz, ClCH2CH2–), 1.58–1.40 (m, 2H, –CH2-
CH2Si), 0.86–0.72 (m, 2H, –CH2Si), 0.31 (s, 6H, H3C–Si)
ppm; 13C NMR (68 MHz; CDCl3) d 139.2, 133.6, 129.0,
127.9, 44.7, 36.2, 21.3, 15.1, K3.0 ppm; 1H NMR
(270 MHz; DMSO-d6) d 7.57–7.40 (m, 2H), 7.40–7.24 (m,
3
3
3H), 3.55 (t, 2H, JZ6.6 Hz), 1.68 (quintuplet, 2H, JZ
6.6 Hz), 1.51–1.24 (m, 2H), 0.78–0.62 (m, 2H), 0.21 (s, 6H)
ppm; 13C NMR (68 MHz; DMSO-d6) d 139.1, 133.8, 129.4,
128.3, 45.4, 36.1, 21.2, 14.8, K2.5 ppm; MS (CIC) m/z 246
and 244 [MCNH4]C; MS (EIC) m/z 213 and 211 [MK
1
1591 cmK1; H NMR (270 MHz; DMSO-d6) d 7.61 (d, 2H,
CH3]C%, 135 [MKC4H8Cl]C%, 172 and 170 [MKC4H8]C%
,
3JZ7.8 Hz, Ar), 7.55 (d, 2H, 3JZ7.8 Hz, Ar), 6.25 (dd, 1H,
3JZ10.6, 19.8 Hz, Si–CH]CHcisHtrans), 6.12 (dd, 1H, 2JZ
4.4 Hz, 3JZ10.6 Hz, Si–CH]CHcisHtrans), 5.76 (dd, 1H,
2JZ4.4 Hz, 3JZ19.8 Hz, Si–CH]CHcisHtrans), 4.57 (s, 2H,
ArCH2–), 3.05 (s, 9H, –NC(CH3)3), 1.40–1.13 (m, 8H, alk),
0.94–0.70 (m, 10H, alk) ppm; 13C NMR (68 MHz; DMSO-d6)
d 139.5, 135.8, 135.1, 135.1, 132.7, 129.6, 68.1 (ArCH2–),
52.4 (–NC(CH3)3), 26.5, 26.0, 14.2, 11.9 ppm; MS (FABC)
m/z 318 [MKI]C; HRMS (FABC) m/z calculated for
C20H36NSi [MKI]C 318.2617, found 318.2633.
157 and 155 [MKC5H11]C%
.
4.3.20. Dibutyl(4-chlorobutyl)phenylsilane (27). To a
solution of t-BuLi (43.8 mL, 1.60 M in pentane,
70.0 mmol) in Et2O (20 mL) at K78 8C, 1-chloro-4-
iodobutane11 (4.25 mL, 35.0 mmol) was added dropwise
over 5 min. After a further 1 h, silylsulfonate 29 (11.7 g,
31.8 mmol) was added dropwise over 0100min. The solution
was allowed to warm to K20 8C and N ,N ,N,N-tetramethyl-
ethane-1,2-diamine (10.4 mL, 70.0 mmol) was added
dropwise over 5 min. The solution was allowed to warm
to room temperature and stirred for a further 32 h. Aqueous
NH4Cl solution (60 mL) was added, the layers were
separated and the aqueous layer was extracted with Et2O
(3!60 mL). The combined organics were washed with an
aqueous HCl solution (3!150 mL, 2 M), brine (150 mL),
4.3.18. Sodium {2-[dibutyl-(p-trimethylammonium iod-
ide)benzyl]silyl}ethane sulfonate (25). To a solution of
Na2SO3 (6.1 g, 48.7 mmol) in H2O (9 mL), an aqueous
solution of HCl (4.1 mL, 12 M, 48.7 mmol) was added
dropwise over 10 min. A solution of vinylsilane 24 (6.6 g,
14.8 mmol) in MeOH (9 mL) was added dropwise over

7240
D. C. Braddock, J. J.-P. Peyralans / Tetrahedron 61 (2005) 7233–7240
dried over MgSO4 and concentrated to afford (4-chlorobu-
tyl)silane 27 (9.3 g, 30 mmol, 94%) as a light yellow oil: IR
References and notes
1
(neat) nmax 3068, 3049, 2956, 2924, 2858 cmK1; H NMR
(270 MHz; CDCl3) d 7.52–7.44 (m, 2H, Ar), 7.40–7.31 (m,
1. See, for example, trimethylsilyl trifluoromethanesulphonate
Sweeney, J.; Perkins, G. In Paquette, L. A., Ed.; Encyclopae-
dia of reagents for organic synthesis; Wiley: New York, 1995;
Vol. 7, pp 5315–5319.
3H, Ar), 3.52 (t, 2H, 3JZ7.0 Hz, ClCH2–), 1.79 (quintuplet,
3
2H, JZ7.0 Hz, ClCH2CH2–), 1.54–1.40 (m, 2H, ClCH2-
CH2CH2–), 1.40–1.15 (m, 8H, alk), 0.99–0.72 (m, 12H, alk
and ClCH2CH2CH2CH2–) ppm; 13C NMR (68 MHz;
CDCl3) d 137.7, 134.1, 128.8, 127.8, 44.6 (ClCH2–), 36.4
(ClCH2CH2–), 26.8, 26.1, 21.2 (ClCH2CH2CH2–), 13.8,
12.1, 11.8(ClCH2CH2CH2CH2–)ppm;MS(CIC) m/z330and
328 [MCNH4]C; HRMS (CIC) m/z calculated for C18H35-
NSi35Cl [MCNH4]C 328.2227, found 328.2226; HRMS
(CIC) m/z calculated for C18H35NSi37Cl [MCNH4]C
330.2198, found 330.2211.
2. (a) Dubac, J.; Mazerolles, P. Bull. Soc. Chim. Fr. 1969,
3608–3609. (b) Dubac, J.; Mazerolles, P. J. Organomet. Chem.
1969, 20, P5–P6. (c) Dubac, J.; Mazerolles, P.; Joly, M.
J. Organomet. Chem. 1970, 22, C7–C8. (d) Dubac, J.;
Mazerolles, P.; Lesbre, M.; Joly, M. J. Organomet. Chem.
1970, 25, 367–384. (e) Dubac, J.; Mazerolles, P.; Joly, M.
J. Organomet. Chem. 1978, 153, 289–298. (f) Grignon-Dubois,
M.; Dunogues, J.; Duffaut, N.; Calas, R. J. Organomet. Chem.
1980, 188, 311–319.
3. (a) Matsumoto, K.; Mizuno, U.; Matsuoka, H.; Yamaoka, H.
Macromolecules 2002, 35, 555–565. (b) Matsumoto, K.; Aoki,
Y.; Oshima, K.; Utimoto, K.; Rahman, N. A. Tetrahedron
1993, 49, 8487–8502.
4.3.21. Dibutylphenylsilyl trifluoromethanesulfonate
(29). To stirred neat dibutyldiphenylsilane8 (10.9 mL,
35.0 mmol) at K20 8C, trifluoromethylsulphonic acid
(2.81 mL, 31.8 mmol) was added dropwise over 10 min.
The resulting mixture was allowed to warm to room
temperature and stirred for a further 4 h to afford
silylsulfonate 29 (11.7 g, 31.8 mmol, 100%) as a light
4. Scott, R. E.; Frisch, K. C. J. Am. Chem. Soc. 1951, 73,
2599–2600.
5. Weinreb, S. M.; Demko, D. M.; Lessen, T. A.; Demers, J. P.
Tetrahedron Lett. 1986, 27, 2099–2102.
1
orange oil: H NMR (270 MHz; CDCl3) d 7.76–7.66 (m,
2H, Ar), 7.66–7.45 (m, 3H, Ar), 1.63–1.37 (m, 8H, alk),
6. Bhattacharyya, S. Synth. Commun. 2000, 30, 2001–2008.
7. Negishi, E.-i.; Swanson, D.; Rousset, C. J. J. Org. Chem. 1990,
55, 5406–5409.
1.10–0.98 (m, 10H, alk) ppm; 13C NMR (68 MHz; CDCl3) d
1
135.0, 133.8, 131.6, 128.4, 118.6 (q, JCFZ318 Hz, CF3),
26.2, 24.4, 13.5, 13.3 ppm; MS (EIC) m/z 368 [M]C%, 311
[MKC4H9]C%, 181 [MKC4H9-F3CSO3CF]C%, HRMS
(EIC) calculated for C15H23O3F3SSi [M]C% 368.1089,
found 368.1095.
8. Topchiev, A. V.; Nametkin, N. S.; Gu, C.-L.; Leonova, N. A.
Dolk. Akad. Nauk. SSSR 1958, 118, 731–734.
9. Matyjaszewski, K.; Chen, Y. L. J. Organomet. Chem. 1988,
340, 7–12.
10. Denmark, S. E.; Griedel, B. D.; Coe, D. M.; Schnute, M. E.
J. Am. Chem. Soc. 1994, 116, 7026–7043.
11. Hahn, R. C. J. Org. Chem. 1988, 53, 1331–1333.
12. Aldrich Catalogue Handbook of Fine Chemicals.
13. Wilt, J. W.; Dockus, C. F. J. Am. Chem. Soc. 1970, 92,
5813–5814.
Acknowledgements
We thank the EPSRC for a Fast Stream Grant (GR/
M88143).