Titanocene-mediated homolytic opening of epoxysilanes

Article abstract of DOI:10.1002/hlca.200690213

The titanocene(III) chloride mediated opening of silyloxiranes has been examined. Electron transfer from the metal leads to α-silyl radicals with total regiocontrol. The radicals could be trapped by various olefins, and the corresponding adducts were obtained in good yields (Table). Further substitution of the oxirane by alkyl groups proved detrimental to the reactions, but ring opening remained essentially regioselective.

Full text of DOI:10.1002/hlca.200690213

Helvetica Chimica Acta – Vol. 89 (2006)
2297
Titanocene-Mediated Homolytic Opening of Epoxysilanes
by Nicolas Puljic, Matthias Albert, Anne-Lise Dhimane, Louis Fensterbank*, Emmanuel Lacôte*,
and Max Malacria*
UniversitØ Pierre et Marie Curie-Paris 6, Institut de chimie molØculaire (FR 2769), Laboratoire de
chimie organique (UMR CNRS 7611), 4 place Jussieu, C. 229, F-75005 Paris
(
fax: +33 1 44 27 73 60; e-mail: louis.fensterbank@upmc.fr, lacote@ccr.jussieu.fr, and
max.malacria@upmc.fr)
Dedicated to the memory of Professor Hanns Fischer, whose outstanding contribution to radical
chemistry has made it an essential asset of modern chemistry
The titanocene(III) chloride mediated opening of silyloxiranes has been examined. Electron transfer
from the metal leads to a-silyl radicals with total regiocontrol. The radicals could be trapped by various
olefins, and the corresponding adducts were obtained in good yields (Table). Further substitution of the
oxirane by alkyl groups proved detrimental to the reactions, but ring opening remained essentially regio-
selective.
Introduction. – Introduction of titanocene(III) chlorides as effective reagents for
the homolytic opening of epoxides – leading to b-titanoxy alkyl radicals – is arguably
one of the most-significant breakthroughs in radical chemistry of the past two decades.
Indeed, Nugent and RajanBabu [1] reported in 1988 that titanocene(III) chloride can
transfer one electron to oxiranes, which regioselectively leads to the most substituted
b-titanoxyl radical after opening of the strained three-membered ring. Gansäuer et
al. have shown that this system is amenable to asymmetric catalysis [2][3]. Those
two outstanding contributions have opened vast new opportunities for chemists. Inter-
est for this new system stems in no small part from the fact that it avoids the use of Sn
derivatives – relying on nontoxic metals instead – and it creates radicals from oxiranes,
which can be obtained easily, and using green reactions, too. The number of reports
focusing on this particular aspect of Ti chemistry has thus soared over these last four
years. Yet, research has so far been focused on mechanistic elucidations [4–7], varia-
tions of the catalysts [8–10], and the scope of the b-titanoxyl radical addition to unsa-
turated compounds [11][12] from intermolecular additions [13–15] and cyclizations
[
13][16][17] to polycyclization cascades leading to natural products [18–20] and
other domino processes [21][22].
To the best of our knowledge, little attention has been given to the oxirane substi-
tution beyond the initial determination of the openingꢀs regioselectivity. Introduction
of heteroatoms on the small ring might both modulate the reactivity and allow further
functionalization after the radical step. In this respect, silicon groups are attractive can-
didates. Because of their steric bulk, they might direct the opening of the oxiranes
toward the formation of a-silyl radicals, which could further react with olefins to create
ꢁ
2006 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 89 (2006)
various C,C bonds; Tamao–Fleming oxidation of the CÀSi bond would afford the cor-
responding alcohols [23]. Overall, epoxysilanes are potential synthetic equivalents of b-
hydroxy ketyl radicals and might provide an entry to polyhydroxylated compounds
(Scheme 1). We report herein our progress along these lines.
Scheme 1. Epoxysilanes as Potential Equivalents of b-Hydroxy Ketyl Radicals
Results and Discussion. – We started our work with a series of monosubstituted
silyloxiranes 1 (Table). Reactions were carried out using a stoichiometric amount of
A
H
R
U
G
titanocene(IV) dichloride in the presence of powdered Zn and an acceptor (2
equiv.). In all cases, only formation of the a-silyl radical addition products (compounds
2
–15) were observed. The regiochemical outcome of the reaction is in agreement with
what has been previously observed with nonsymmetric oxiranes. Indeed, opening is
directed by nonbonding interactions during electron transfer, i.e., on the Ti/oxirane
complex (Scheme 2) [7 ].
Scheme 2. Origin of the Regioselectivity of the Ring Opening of Epoxysilanes
The absence of the minor regioisomer might be attributed to the increased steric
hindrance brought by the silyl group. Although CÀSi bonds are longer than CÀC
ones by 20%, steric control would still be effective (the total selectivity may also be
the consequence of a degradation of regioisomer A, which is suitable for a Brook rear-
rangement). It has to be noted that stabilization of radicals by silyl groups is still a mat-
ter of debate [24] and might play also a role, even if the literature on homolytic open-
ings of oxiranes by titanocene(III) complexes has excluded such a possibility for normal
oxiranes [7][11].
Several olefins have been used throughout this study: acrylonitrile (Table, Entries 1,
5
1
, 10, 11, and 14), vinylsulfones (Entries 2 and 6), or acrylates (Entries 3, 4, 7–9, 12, and
3). The yields were medium to good, reflecting those generally obtained with standard
oxiranes. Lactonization was observed with methyl acrylates (Entries 3, 7, 9, and 12), but
we could get the opened product with the tert-butyl acrylates (Entries 4, 8, and 13).
However, in those cases, the yields were lower. Maybe some of the adducts were lost
upon acidic hydrolysis. We next looked at the substitution on silicon. Different combi-
nations were tried, and all gave similar results. Heavier silyloxiranes gave some deoxy-
genated vinylsilanes 16b–e (11–20%) [25]. This was not observed with oxirane 1a,
probably because of the volatility of 16a (b.p. 558).
We next studied the influence of further substitution on the oxirane moiety.
Because our ultimate goal is to prepare polyhydroxylated compounds, we decided to

Helvetica Chimica Acta – Vol. 89 (2006)
2299
Table. Titanocene-Mediated Homolytic Opening of Epoxysilanes. Conditions: Cp TiCl (2 equiv.), Zn
2
2
dust (5 equiv.), olefin (2 equiv.).
Entry Substrate Olefin
Product
Yield [%] Side product (yield [%])
1
2
3
1a
1a
1a
2
3
4
7
3
–
7
1
–
84
–
–
4
5
6
7
1a
1b
1b
1b
5
6
7
8
56
7
5
–
65
60
–
16b (12)
8
1b
9
48
–

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300
Helvetica Chimica Acta – Vol. 89 (2006)
Table (cont.)
Entry Substrate Olefin
Product
Yield [%] Side product (yield [%])
9
1b
10 60a)
16b (12)
10
11
12
1c
1d
1d
11 57
12 64
13 62
16c (15)
16d (14)
16d (20)
1
1
3
1d
1e
14 50
16d (14)
16e (11)
b
4 )
15 61
a) Diastereoisomer ratio (ds) ca. 1:1. ) Mn instead of Zn dust was used.
b
continue with a silyl moiety that could undergo oxidation. We opted for the phenyldi-
methylsilyl derivatives 17–19, with different steric hindrance (cis and trans relative
configurations, increased bulk).
Unfortunately, no reaction proceeded as anticipated. Besides, the substratesꢀ
behavior toward different olefins was far from clear, and could not be rationalized.
Complex mixtures were obtained, and the only observable products were, in some
cases, acrylonitrile (the remaining starting material, up to 86%), and in other cases
acrylates (an increased amount of deoxygenated products, up to 75%). Overall, it
seems that increased steric hindrance is detrimental to the addition process. This was

Helvetica Chimica Acta – Vol. 89 (2006)
2301
further confirmed in the case of the trisubstituted substrate 20 (Scheme 3). The only iso-
lated product was the silylated allyl alcohol 21, which was isolated in 83% yield. Its for-
mation could be rationalized by a b-hydride elimination of the intermediate 22, which
would originate from the reduction of radical 23. The latter could be too congested to
allow the desired addition on the double bond. If this is the case, the opening of 20
would still be totally regioselective. Alternatively, the elimination could have been
mediated by the Lewis acid (ZnCl ) produced during the reduction of titanocene
2
dichloride [26]. We are currently assessing this issue.
Scheme 3. Possible Mechanism for the Reaction of 20
We finally examined the catalytic version (Scheme 4). To our surprise, the reactions
with acrylonitrile were rather sluggish. The major products were the lactones arising
from the acid-catalyzed or Lewis acid catalyzed activation of the nitrile moiety during
the reaction. The overall yields were lower than with stoichiometric Ti complexes
(maybe because of loss of an intermediate hydroxy carboxylic acid). Clearly, an optimi-
zation is required, but this shows nonetheless that catalysis is feasible.
Scheme 4. Preliminary Examples of Catalytic Reactions
Conclusions. – Silyloxiranes can be regioselectively opened by titanocene(III) com-
plexes. Provided steric hindrance on the oxirane moiety is not too important, addition
of the resulting a-silyl radicals onto olefins can take place. Our initial work has shown
that steric hindrance is a predominant factor. We could show that the system is amena-
ble to catalysis. We are now focusing on establishing precisely the scope of the reaction,

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302
Helvetica Chimica Acta – Vol. 89 (2006)
notably by introducing trialkylsilyl vinyloxiranes [27]. This will be presented in due
course.
This work was supported by UPMC, CNRS, and IUF (of whom M. M. is a senior member). N. P.
thanks the minist›re de lꢀenseignement supØrieur et de la recherche for a grant. M. A. thanks CNRS for
a postdoctoral fellowship. Technical support from ICSN (Gif sur Yvette, France) is gratefully acknowl-
edged (HR-MS and elemental analyses). We are indebted to Prof. Mike E. Jung (UCLA, USA) for fruit-
ful discussions.
Experimental Part
General. Reactions were carried out under inert gas, with magnetic stirring, using redistilled,
degassed solvents when necessary. THF was distilled from Na/benzophenone. Cp TiCl (97%) was pur-
2
2
chased from Aldrich and used as received. Manganese (Mn, À325 mesh; >99%) was purchased from
Strem and used without further purification. Zn Dust (À325 mesh) was purchased from Aldrich and puri-
fied according to the following procedure: Zn (120 mg) was stirred for 1 min with aq. 2% HCl (300 ml).
The acid was removed by filtration, and the powder was washed with aq. 2% HCl (300 ml), dist. H O (300
2
ml), 95% EtOH (400 ml), and Et2O (200 ml). The material was finally thoroughly dried. Acrylonitrile
A
H
R
N
was dried over CaCl and distilled immediately before use. Methyl acrylate was purchased from Aldrich,
2
washed repeatedly with aq. 1M NaOH, then with dist. H O, dried (CaCl ), and distilled under reduced
2
2
pressure before use. Phenyl vinyl sulfone (99%) and tert-butyl acrylate (>98%) were purchased from
Aldrich and used without further purification. The starting silyloxiranes were prepared according to
the literature [28].
Thin-layer chromatography (TLC) was performed on silica gel 60 F254 (Merck). Geduran SI 60 A
silica gel (35–70 mm; Merck) was used for flash column chromatography (FC). The abbreviation ꢂPEꢀ
is used for petroleum ether. Melting points (m.p.) were measured with a Reichert hot-stage apparatus
and are uncorrected. IR Spectra were recorded on a Bruker Tensor 27 ATR diamant PIKE spectrometer;
À1
1
13
in cm . H- and C-NMR Spectra were recorded at r.t. on 200/50 MHz Bruker AC-200 and ARX-200
spectrometers, on a 250/62.5 MHz Bruker ARX-250 apparatus, and on 400/100 MHz Bruker ARX-400
and AVANCE-400 spectrometers, resp.; chemical shifts d in ppm rel. to residual solvent signals of
CDCl3 (d(H) 7.26, d(C) 77.0), coupling constants J in Hz. High-resolution mass spectra (HR-MS)
were recorded at ICSN (CNRS, Gif) on an LCT micromass apparatus (electrospray source). Elemental
analyses were performed by the Service RØgional de Microanalyse de lꢀUniversitØ Pierre et Marie Curie,
and at ICSN (CNRS, Gif).
General Procedure (GP) for Cp TiCl-Mediated Reactions. Cp TiCl (498 mg, 2.0 mmol, 2.0 equiv.)
2
2
2
and Zn powder (296 mg, 5.0 mmol, 5.0 equiv.) were added to degassed THF (15 ml) at r.t. The mixture
turned greenish, and the supernatant was cannulated to a degassed soln. of the starting silyloxirane (1.0
mmol, 1.0 equiv.) and the olefin acceptor (2.0 mmol, 2.0 equiv.). After completion of the reaction (ca. 30
min), the mixture was diluted with Et O (10 ml), and quenched with 10% aq. H SO soln. (ca. 15 ml),
A
H
R
U
2
2
4
washed twice with sat. aq. NaHCO soln. (40 ml) and brine (20 ml), dried (MgSO ), and concentrated
3
4
in vacuo. The crude product was purified by FC (SiO ) and, in some cases, separated from the corre-
2
sponding vinylsilanes (see main text and the Table).
5
-Hydroxy-4-(trimethylsilyl)pentanenitrile (2). Purified by FC (SiO ; PE/Et
A
H
R
U
G
2
1
(
(
73%). Yellow oil. IR (neat): 3445, 2950, 2240. H-NMR (400 MHz, CDCl ): 0.03 (s, Me
A
T
E
N
3
m, SiCH); 1.77–1.88 (m, CH CH CN); 2.53–2.58 (m, CH CN); 3.65 (B of ABX, J=10.8, 8.1, 1 H of
2
2
2
13
OCH ); 3.89 (A of ABX, J=10.8, 3.5, 1 H of OCH ). C-NMR (75 MHz, CDCl ): À2.5 (Me
A
H
R
U
G
2
2
3
(CH CH CN); 24.6 (CH CN); 29.4 (SiCH); 63.6 (CH O); 120.4 (CN). HR-ESI-MS: 194.0988
2
2
2
+
2
+
(
[M+Na] , C
A
H
R
U
H
A
H
R
U
G
8
17
4
-(Phenylsulfonyl)-2-(trimethylsilyl)butan-1-ol (3). Purified by FC (SiO ; PE/AcOEt 70 :30). Yield:
2
1
2
0
3
03 mg (71%). Orange oil. IR (neat): 3522, 2950, 1085. H-NMR (400 MHz, CDCl ): À0.01 (s, Me
A
H
R
U
G
3
.93–0.99 (m, SiCH); 1.81–1.88 (m, 1 H of CH CH CN); 1.93–1.99 (m, 1 H of CH CH CN);
2
2
2
2
2 2 2 2
.16–3.24 (m, 1 H of CH SO ); 3.38–3.45 (m, 1 H of CH SO ), 3.59 (B of ABX, J=10.8, 8.1, 1 H of

Helvetica Chimica Acta – Vol. 89 (2006)
2303
OCH ); 3.84 (A of ABX, J=10.8, 3.5, 1 H of OCH ); 7.57–7.67 (m, 3 arom. H); 7.88–7.90 (m, 2 arom. H).
2
2
1
3
C-NMR (75 MHz, CDCl ): À2.5 (Me
A
H
R
U
3
(
3
CH O); 128.0 (arom. CH); 129.2 (arom. CH); 133.6 (arom. CH); 154.0 (arom. C). HR-ESI-MS:
2
+ +
09.0912 ([M+Na] , C
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
1
3
22
found: C 54.06, H 7.71.
Tetrahydro-5-(trimethylsilyl)-2H-pyran-2-one (4). Purified by FC (SiO ; PE/Et
mg (84%). Yellow oil. IR (neat): 2952, 1731, 1077. H-NMR (400 MHz, CDCl ): 0.06 (s, Me
A
H
R
U
G
2
1
A
H
R
U
3
1
.21–1.28 (m, SiCH); 1.64–1.78 (m, 1 H of CH CH C=O); 1.90–1.99 (m, 1 H of CH CH C=O); 2.46
2 2 2 2
(
B of ABXY, J=17.7, 10.0, 7.4, 1 H of CH C=O); 2.63 (A of ABXY, J=17.7, 6.6, 3.5, 1 H of CH C=
2
2
13
O); 4.18 (B of ABX, J=12.9, 11.4, 1 H of OCH ); 4.46 (A of ABX, J=11.4, 2.3, 1 H of OCH ). C-
2
2
NMR (75 MHz, CDCl ): À3.4 (Me
A
T
E
N
3
(
OCH ); 171.5 (C=O). Anal. calc. for C H O Si: C 55.77, H 9.36; found: C 55.56, H 9.12.
2 8 16 2
1
,1-Dimethylethyl 5-Hydroxy-4-(trimethylsilyl)pentanoate (5). Purified by FC (SiO ; PE/Et
A
H
R
U
G
2
1
7
0 :30). Yield: 138 mg (56%). Yellow oil. IR (neat): 3434, 2952, 1726, 1148, 833. H-NMR (400 MHz,
CDCl ): 0.03 (s, Me
A
H
R
U
G
A
T
E
N
3
3
J=7.3, CH C=O); 3.63 (B of ABX, J=10.9, 7.6, 1 H of OCH ); 3.79 (A of ABX, J=10.9, 3.6, 1 H of
2
2
13
OCH ). C-NMR (75 MHz, CDCl ): À2.3 (Me
A
H
R
U
G
2
3
3
5.2 (CH C=O); 63.3 (OCH ); 80.4 (Me C); 173.9 (C=O). Anal. calc. for C H O Si: C 58.49, H
2 2 3 12 26 3
1
0.63; found: C 58.75, H 10.51.
4
-[Dimethyl(phenyl)silyl]-5-hydroxypentanenitrile (6). Purified by FC (SiO ; PE/Et
A
T
E
N
2
1
1
75 mg (75%). Yellow oil. IR (neat): 3431, 2954, 2246, 814. H-NMR (400 MHz, CDCl ): 0.34 (s, 3 H of
3
Me
A
H
R
U
G
A
H
R
U
G
2
2
2
2
CH
2
CN); 3.66 (B of ABX, J=10.6, 7.8, 1 H of OCH
2
); 3.88 (A of ABX, J=10.6, 3.5, 1 H of OCH
2
);
1
3
7
.32–7.41 (m, 3 arom. H); 7.48–7.56 (m, 2 arom. H). C-NMR (75 MHz, CDCl ): À4.3 (1 C of Me
ACHTREUNG
Si);
3
2
À4.1 (1 C of Me
A
H
E
N
(
(
arom. CH); 129.5 (arom. CH); 133.7(arom. CH); 136.9 (arom. C). HR-ESI-MS: 256.1100
+ +
[M+Na] , C
A
H
R
U
G
A
T
E
N
13
found: C 66.59, H 8.07, N 5.75.
2
-[Dimethyl(phenyl)silyl]-4-(phenylsulfonyl)butan-1-ol (7). Purified by FC (SiO ; PE/AcOEt
2
1
7
0 :30). Yield: 227 mg (65%). Yellow oil. IR (neat): 3525, 3068, 2923, 1146, 818. H-NMR (400 MHz,
CDCl ): 0.29 (s, 3 H of Me
A
H
R
U
G
A
T
E
N
3
2
3
.10 (B of ABXY, J=13.9, 10.2, 5.9, 1 H of CH SO ); 3.29 (A of ABXY, J=13.9, 10.1, 5.0, 1 H of
2 2
CH SO ); 3.59 (B of ABX, J=10.9, 8.3, 1 H of OCH ); 3.82 (A of ABX, J=10.9, 3.6, 1 H of OCH );
2
2
2
2
7
.31–7.40 (m, 3 arom. H); 7.41–7.45 (m, 2 arom. H); 7.50–7.56 (m, 2 arom. H); 7.61–7.66 (m, 1
13
arom. H); 7.81–7.84 (m, 2 arom. H). C-NMR (75 MHz, CDCl ): À4.2 (1 C of Me
A
H
R
U
G
3
2
2
A
C
H
T
R
E
U
N
G
Si); 21.2 (CH CH SO ); 28.9 (SiCH); 56.1 (CH SO ); 63.7(OCH ); 128.0 (arom. CH); 128.0 (arom. CH);
2 2 2 2 2 2
1
29.2 (arom. CH); 129.4 (arom. CH); 133.6 (arom. CH); 133.7(arom. CH); 137.0 (arom. C); 139.1 (arom.
+ +
C). HR-ESI-MS: 371.1074 ([M+Na] , C
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
18
24
6
2.03, H 6.94; found: C 61.65, H 6.93.
5
-[Dimethyl(phenyl)silyl]tetrahydro-2H-pyran-2-one (8). Purified by FC (SiO ; PE/Et
A
H
R
U
G
2
1
Yield: 141 mg (60%). Yellow oil. IR (neat): 2953, 1731, 813. H-NMR (400 MHz, CDCl ): 0.35 (s, Me -
3
2
A
C
H
T
R
E
U
N
G
Si); 1.41–1.49 (tt, J=12.9, 4.5, SiCH); 1.63–1.76 (m, 1 H of CH CH C=O); 1.87–1.98 (m, 1 H of
2 2
CH CH C=O); 2.43 (B of ABXY, J=17.7, 10.2, 7.3, 1 H of CH C=O); 2.58 (A of ABXY, J=17.7, 6.6,
2
2
2
3
2
.8, 1 H of CH C=O); 4.15 (B of ABX, J=12.9, 11.4, 1 H of OCH ); 4.42 (A of ABX, J=11.4, 4.5,
2
2
13
.2, 1 H of OCH ); 7.35–7.42 (m, 3 arom. H); 7.44–7.49 (m, 2 arom. H). C-NMR (75 MHz, CDCl ):
2
3
À5.1 (1 C of Me
A
T
E
N
Si); À5.0 (1 C of Me
A
T
E
N
2
(
OCH ); 128.2 (arom. CH); 129.8 (arom. CH); 133.7(arom. CH); 125.4 (arom. C); 1 71 .4 (C =O).
2
1
,1-Dimethylethyl 4-[Dimethyl(phenyl)silyl]-5-hydroxypentanoate (9). Purified by FC (SiO ; PE/Et
A
H
R
U
G
2
1
7
0 :30). Yield: 148 mg (48%). Yellow oil. IR (neat): 3434, 2976, 1725, 1150, 814. H-NMR (200 MHz,
CDCl ): 0.33 (br. s, Me Si); 0.98–1.13 (m, SiCH); 1.42 (s, t-Bu); 1.63–1.82 (m, CH CH C=O); 2.28 (t,
A
H
R
U
G
3
2
2
2
J=7.3, CH C=O); 3.62 (B of ABX, J=11.1, 6.9, 1 H of OCH ); 3.77 (A of ABX, J=11.1, 3.9, 1 H of
2
2
1
3
OCH ); 7.30–7.39 (m, 3 arom. H); 7.46–7.58 (m, 2 arom. H). C-NMR (75 MHz, CDCl ): À3.9 (1 C
2
3
of Me
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
2
2
2
2

2
304
Helvetica Chimica Acta – Vol. 89 (2006)
(
(
OCH ); 80.4 (Me C); 127.9 (arom. CH); 129.1 (arom. CH); 133.9 (arom. CH); 138.0 (arom. C); 173.9
2
2
+
+
C=O). HR-ESI-MS: 331.1682 ([M+Na] , C
A
H
R
U
G
A
T
E
G
A
T
E
N
17
28
C 66.19, H 9.15; found: C 66.15, H 9.38.
-[Dimethyl(phenyl)silyl]tetrahydro-3-methyl-2H-pyran-2-one (10). Purified by FC (SiO ; PE/Et O
2
5
A
H
R
U
G
2
8
1
0 :20). Yield: 149 mg (60%; mixture of inseparable diastereoisomers). Yellow oil. IR (neat): 2956,
1
730, 1171, 818. H-NMR (400 MHz, CDCl ): 0.31 (s, 1 C of Me
A
H
R
U
G
A
H
R
U
3
2
of one isomer); 0.35 (s, 1 C of Me2
A
H
R
U
G
A
H
R
U
MeCH, isomer B); 1.25 (d, J=7.1, MeCH, isomer A); 1.35–1.45 (m, 1 H of CH2
AHCTREUNG
1
1
.50–1.64 (m, 1 H of CH2
.94–2.04 (m, CH2
ACHTREUNG
AHCTREUNG
B); 4.14 (B of ABX, J=12.6, 11.4, 1 H of OCH , isomer B); 4.18 (B of ABX, J=12.4, 11.4, 1 H of
2
OCH , isomer A); 4.29 (A of ABX, J=11.4, 4.8, 1.3, 1 H of OCH , isomer B); 4.41 (A of ABX,
2
2
J=11.4, 4.8, 2.5, 1 H of OCH , isomer A); 7.31–7.43 (m, 6 arom. H, isomers A and B); 7.45–7.55 (m,
2
13
4
arom. H; isomers A and B). C-NMR (75 MHz, CDCl ): À5.1 (Me
A
H
R
U
G
3
À4.9 (Me
A
H
R
U
G
B); 24.2 (SiCH, isomer A); 28.4 (CH CHC=O, isomer B); 30.5 (CH CHC=O, isomer A); 33.8
2
2
(
(
MeCH, isomer B); 37.8 (MeCH, isomer A); 69.7(OCH , isomer B); 72.6 (OCH , isomer A); 128.2
arom. CH, isomers A and B); 129.8 (arom. CH., isomers A and B); 133.7(arom. CH, isomers A and
2
2
B); 135.5 (arom. C, isomers A and B); 174.4 (C=O, one isomer); 176.2 (C=O, one isomer). HR-ESI-
+
+
MS: 271.1124 ([M+Na] , C
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
1
4
20
5
-Hydroxy-4-[methyl(diphenyl)silyl]pentanenitrile (11). Purified by FC (SiO ; PE/Et O 80 :20).
A
H
R
U
G
2
1
2
Yield: 168 mg (57%). Yellow oil. IR (neat): 3427, 3069, 2927, 2246, 1588, 1108. H-NMR (400 MHz,
CDCl ): 0.63 (s, MeSi); 1.66–1.73 (m, SiCH); 1.80–1.98 (m, CH CH CN); 2.48 (t-like, J=7.6,
CH CN); 3.69 (B of ABX, J=10.8, 7.7, 1 H of OCH ); 3.93 (A of ABX, J=10.8, 3.3, 1 H of OCH );
3
2
2
2
2
2
13
7
(
.34–7.44 (m, 6 arom. H); 7.48–7.59 (m, 4 arom. H). C-NMR (75 MHz, CDCl ): À5.4 (MeSi); 17.7
3
2 2 2 2
CH CH CN); 24.5 (CH CN); 27.7 (SiCH); 63.3 (OCH ); 120.2 (CN); 128.1 (arom. CH); 128.2 (arom.
CH); 129.7(arom. CH); 129.7(arom. CH); 134.6 (arom. CH); 134.6 (arom. CH); 134.9 (arom. C);
34.9 (arom. C).
-Hydroxy-4-(triphenylsilyl)pentanenitrile (12). Purified by FC (SiO ; CH Cl /Et O 95 :5). Yield: 229
2
1
5
A
H
R
U
G
2
2
2
1
mg (64%). Colorless solid. M.p. 126–1288. IR (neat): 3479, 3069, 2931, 2245, 1109. H-NMR (400 MHz,
CDCl ): 1.85–1.96 (m, SiCH); 2.03–2.18 (m, CH CH CN); 2.50–2.64 (m, CH CN); 3.77–3.81 (m, 1 H of
OCH ); 4.07–4.10 (m, 1 H of OCH ); 7.36–7.49 (m, 9 arom. H); 7.50–7.64 (m, 6 arom. H). C-NMR (75
3
2
2
2
13
2
2
MHz, CDCl ): 17.9 (CH CH CN); 25.3 (CH CN); 27.2 (SiCH); 63.6 (OCH ); 120.1 (CN); 128.2 (arom.
3
2
2
2
2
+
CH); 129.9 (arom. CH); 133.1 (arom. C); 135.8 (arom. CH): HR-ESI-MS: 380.1448 ([M+Na] , C H -
NNaOSi ; calc. 380.1447).
A
H
R
U
23 23
+
A
C
H
T
R
E
U
N
G
Tetrahydro-5-(triphenysilyl)-2H-pyran-2-one (13). Purified by FC (SiO ; CH Cl /Et
22 mg (62%). Colorless solid. M.p. 144–1478. IR (neat): 2947, 1730, 1107. H-NMR (400 MHz, CDCl ):
A
H
R
U
G
2
1
2
2
2
2
1
1
7
.83–1.96 (m, SiCH); 2.13–2.30 (m, CH CH C=O); 2.46–2.61 (m, CH C=O); 4.26 (B of ABX, J=12.8,
2
2
2
1.6, 1 H of OCH ); 4.64 (A of ABX, J=11.6, 4.6, 2.2, 1 H of OCH ); 7.31–7.50 (m, 9 arom. H);
2
2
13
.50–7.59 (m, 6 arom. H). C-NMR (75 MHz, CDCl ): 21.1 (SiCH); 21.7( CH CH C=O); 30.9
3
2
2
(
1
CH C=O); 71.8 (OCH ); 128.4 (arom. CH); 130.2 (arom. CH); 132.0 (arom. C); 135.7(arom. CH);
2 2
+ +
71.5 (C=O). HR-ESI-MS: 381.1278 ([M+Na] , C
A
H
R
N
H
A
H
R
U
G
A
H
R
U
G
23
22
1
,1-Dimethylethyl 5-Hydroxy-4-(triphenylsilyl)pentanoate (14). Purified by FC (SiO ; CH Cl /Et O
A
H
R
U
2
2
2
2
1
9
5 :5). Yield: 216 mg (50%). Yellow oil. IR (neat): 3434, 2977, 1721, 1589, 1107. H-NMR (400 MHz,
CDCl ): 1.42 (s, t-Bu); 1.83–1.94 (m, SiCH, 1 H of CH CH C=O); 1.98–2.02 (m, OH); 2.06–2.13 (m,
3
2
2
1
H of CH CH C=O); 2.32–2.39 (m, CH C=O); 3.76–3.83 (m, 1 H of OCH ); 3.96–4.03 (m, 1 H of
2
2
2
2
13
OCH ); 7.34–7.45 (m, 9 arom. H); 7.55–7.60 (m, 6 arom. H). C-NMR (75 MHz, CDCl ): 23.4
2
3
(
CH CH C=O); 28.1 (Me C); 35.3 (CH C=O); 63.1 (OCH ); 80.5 (t-Bu); 128.0 (arom. CH); 129.6
3 2 2
+
A
H
R
U
G
2
2
(
arom. CH); 133.9 (arom. C); 136.0 (arom. CH); 173.7 (C=O). HR-ESI-MS: 455.1997([ M+Na] , C -
27
+
A
C
H
T
R
E
U
N
G
H
A
H
R
U
G
A
T
E
N
32
5
-Hydroxy-4-[tris(1-methylethyl)silyl]pentanenitrile (15). Purified by FC (SiO ; CH Cl /AcOEt
2 2 2
9
0 :10). Yield: 156 mg (61%). Colorless solid. M.p. 41–428. IR (neat): 3501, 2942, 2866, 2249, 1006.
1
H-NMR (400 MHz, CDCl ): 1.03–1.16 (m, 3 i-Pr); 1.39–1.45 (m, 1 H, SiCH); 1.82–1.91 (m, 1 H of
3

Helvetica Chimica Acta – Vol. 89 (2006)
2305
CH CH CN); 1.99–2.06 (m, 1 H of CH CH CN); 2.63 (B of ABXY, J=16.7, 8.3, 8.3, 1 H of CH CN);
2
2
2
2
2
2
4
.75 (A of ABXY, J=16.7, 8.2, 4.8, 1 H of CH CN); 3.75 (B of ABX, J=10.7, 9.7, 1 H of OCH );
2 2
13
.02–4.05 (m, 1 H of OCH ). C-NMR (75 MHz, CDCl ): 11.0 (Me CH); 19.0 (Me CH); 19.1
A
H
R
U
G
2
3
2
2
(
CH CH CN); 26.9 (CH CN); 27.2 (CH CHSi); 65.2 (CH O); 120.6 (CN). Anal. calc. for C H NOSi:
2 2 2 2 2 14 29
C 65.82, H 11.44; found: C 65.82, H 11.55.
3
-[Dimethyl(phenyl)silyl]but-3-en-2-ol (21). Purified by FC (SiO ; PE/Et
A
H
R
U
G
2
1
(
83%). Yellow oil. IR (neat): 3376, 3069, 2961, 1110. H-NMR (400 MHz, CDCl ): 0.43 (3 H of Me
A
H
R
U
G
3
0
.44 (3 H of Me2
A
H
R
U
13
(
br. s, 1 H of =CH ); 7.31–7.40 (m, 3 arom. H); 7.51–7.57 (m, 2 arom. H). C-NMR (75 MHz, CDCl ):
2
3
À2.2 (1 C of Me
A
T
E
N
A
H
R
U
G
2
1
29.1 (arom. CH); 133.9 (arom. CH); 138.4 (arom. C); 155.0 (=C). HR-ESI-MS: 229.1019 ([M+Na] ,
+
C1
A
H
R
U
G
ACHTREUNG
2
18
12 18
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Received April 25, 2006