256
F. Badali et al. / Journal of Organometallic Chemistry 575 (1999) 251–260
18b does not manifest in any other significant structural
Table 1
Atomic coordinates and equivalent isotropic displacement parameters
differences, for example the Si–C3 and C3–C2 bonds
do not differ significantly between the two structures.
The silicon directed acid ring opening of
allyltrimethylsilane oxide in low polarity solvents gives
rise to potentially useful hydroxyesters with regio-
chemical control, from what is likely to be reaction
within an intimate ion pair. Reaction in polar solvents,
or in the presence of external nucleophiles results in
significant competing elimination of the silicon.
Incorporation of bulky substituent onto the silicon
removes the problem of elimination in polar solvents,
thus increasing the scope of this reaction as a method
for the formation of hydroxyesters. With the
appropriate substituents attached to silicon, a C–Si
bond can be considered as a latent hydroxy group
˚
2
a
(
A ) for 18b
x/a
y/b
0.20185(4)
z/c
Ueq
Si
0.34082(4)
0.149944(17) 0.01931(10)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
N(1)
N(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
0.67980(11) −0.11191(11) 0.32248(4)
0.90335(13) −0.17349(13) 0.24137(5)
0.48969(13) −0.39958(16) 0.42679(6)
0.54437(13) −0.40887(13) 0.31265(5)
0.99981(14) −0.88793(13) 0.55293(5)
1.26347(14) −0.90354(14) 0.50589(6)
0.01949(19)
0.0324(2)
0.0397(3)
0.0314(2)
0.0302(2)
0.0365(3)
0.0275(2)
0.0243(2)
0.0246(2)
0.0231(3)
0.0202(2)
0.0218(3)
0.0256(3)
0.0338(3)
0.0314(3)
0.0247(3)
0.0335(3)
0.0360(3)
0.0240(3)
0.0321(3)
0.0374(4)
0.0208(2)
0.0189(2)
0.0189(2)
0.0205(2)
0.0208(2)
0.0228(3)
0.0223(3)
0.58878(13)
0.20334(13) 0.37916(5)
0.59022(14) −0.42265(14) 0.37541(6)
1.10234(15) −0.83478(14) 0.50809(6)
0.48220(17)
0.58974(16)
0.47853(17)
0.47746(18)
0.6490(2)
0.16558(17) 0.32770(7)
0.05553(16) 0.27488(7)
0.01477(17) 0.21901(7)
0.35736(18) 0.10422(7)
[17–19], thus simple epoxides similar to 5 might
provide a useful starting point for the preparation of
mixed triesters of glycerol.
0.2564(2)
0.4806(2)
0.07097(9)
0.15209(9)
0.5182(2)
0.14018(17)
0.0314(2)
0.0183(2)
0.33674(18) 0.19471(7)
0.2278(2)
0.4779(2)
0.24480(9)
0.13885(9)
3. Experimental
C(10) 0.28618(17)
C(11) 0.1677(2)
C(12) 0.2110(2)
C(13) 0.82809(16) −0.21147(16) 0.29705(7)
C(14) 0.89569(16) −0.38067(16) 0.35026(6)
C(15) 0.78375(16) −0.47484(16) 0.39028(6)
C(16) 0.84648(17) −0.62250(17) 0.44298(7)
C(17) 1.02993(17) −0.67732(16) 0.45270(6)
C(18) 1.14783(17) −0.59030(17) 0.41406(7)
C(19) 1.07894(17) −0.44060(17) 0.36273(7)
0.08079(18) 0.07857(7)
−0.0451(2)
0.2013(2)
0.10611(8)
0.00756(8)
3.1. Crystallography
Diffraction data were recorded on an Enraf Nonius
CAD4f diffractometer operating in the q/2q scan mode
at low temperature (130.0(1) K) for 12b and 12c. The
crystals were flash cooled to 130.0 K using an Oxford
Cryostream cooling device. Unit cell dimensions were
corrected for any q zero errors by centring reflections at
both positive and negative q angles. The data were
corrected for Lorentz and Polarization effects and for
Absorption (SHELX 76) [20]. Structures were solved by
direct methods (SHELXS-86) [21] and were refined on
a
Ueq is defined as one third of the trace of the orthogonalized Uij
tensor.
2
F (SHELXL-97) [22]. The figures were drawn using the
1
3
C-NMR data for 6a–e: l (CDCl ) are: 6a. 171.27;
3
ZORTEP program [23]. Crystal data and refinement
details for 18b and 18c are listed in Table 4.
1
7
3.84; 66.15; 21.13; 18.82; −1.23; H-NMR: 4.95 (1H,
m); 3.6–3.4 (2H, m); 1.90 (3H, s); 0.9–0.7 (2H, m);
(
–0.10 (9H, s).
b. 164.67; 150.49; 135.76; 130.68; 123.46; 75.98;
6.50; 19.17; −1.00; 8.25 (2H, d, J=7.5 Hz); 8.15 (2H,
3
.2. Synthesis
6
6
General experimental details are reported elsewhere
d, J=7.5 Hz); 5.35 (1H, m); 3.8–3.7 (2H, m); 2.6
(
[16], allyltriisopropylsilane and allyltrimethylsilane were
1H,br S, OH); 1.2–0.95 (2H, m); 0.0 (9H, s).
c. 165.29; 134.31; 132.78; 132.02; 129.55; 129.50;
purchased from Aldrich and used without further
purification. E-1-Trimethylsilyl-2-butene was prepared
as reported [11].
6
1
1
(
27.64; 75.08; 66.26; 19.06; −1.09; H-NMR: l
CDCl ) 7.96 (1H, Br S); 7.88 (1H, Br, D=d, J=7
3
Hz); 7.44 (1H, d, J=7 Hz); 7.29 (1H, dd, J=7 Hz, 7
Hz); 5.31 (1H, m); 4.8 (1H, br, S, OH); 3.8–3.6 (2H,
m); 1.1–0.8 (2H, m); 0.01(9H, s).
3
.3. General procedure for the ring opening of
allyltrimethylsilane oxide 5 with carboxylic acids in
chloroform
6
d. 166.54; 132.77; 130.23; 129.52; 128.14; 74.53;
1
A solution of 50 mg of epoxide 5 in deuterated
66.38; 19.04; −1.09; H-NMR: l (CDCl ) 0.8 (2H, Br,
3
chlorform (0.5 ml) was treated with one equivalent of
d); 7.6–7.2 (3H, m); 5.35 (91H, m); 3.8–3.6 (2H, m);
1.2–0.9 (2H, m); 0.02 (9H, s).
1
the carboxylic acid. Progress was monitored by H- and
1
3
C-NMR, reactions were generally complete within 2
6e. 174.70; 73.74; 66.34; 27.14; 18.92; 8.70; −1.17,
1
days. In all cases the reaction gave rise to one de-
H-NMR: l (CDCl ) 5.0 (1H, m); 3.6–3.4 (2H, m); 2.24
3
tectable product 6a–e
(2H, d); 1.05; 1.05 (3H, t); 0.85 (2H, m); −0.1 (9H, s).