Relative carbanion basicities as driving force for an intramolecular silyl migration of lithiated biphenyls

Article abstract of DOI:10.1016/j.tetlet.2007.10.004

A solvent-dependent silyl migration of lithiated biphenyls is described, involving the intermediate formation of a pentacoordinated silicate complex. Differences in the relative basicities of the aryllithium intermediates are the possible driving force fo

Full text of DOI:10.1016/j.tetlet.2007.10.004

Available online at www.sciencedirect.com
Tetrahedron Letters 48 (2007) 8768–8772
Relative carbanion basicities as driving force for an
intramolecular silyl migration of lithiated biphenyls
a
b
a,
a
*
´ ´
Laurence Bonnafoux, Rosario Scopelliti, Frederic R. Leroux and Franc¸oise Colobert
aLaboratoire de Ste´re´ochimie, Universite´ Louis Pasteur (ECPM), CNRS, 25 rue Becquerel, F-67087 Strasbourg Cedex 2, France
´
Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
b
Received 17 July 2007; revised 25 September 2007; accepted 1 October 2007
Available online 5 October 2007
Abstract—A solvent-dependent silyl migration of lithiated biphenyls is described, involving the intermediate formation of a penta-
coordinated silicate complex. Differences in the relative basicities of the aryllithium intermediates are the possible driving force for
this migration.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Halogen/metal permutations, independently and almost
simultaneously discovered by Wittig1 and Gilman,2 have
been considered for a long while as a mature method
lacking both appeal and surprise. However, the last
years marked a revival. Owing to new insight and tech-
niques, the halogen/metal exchange has recaptured its
former role as one of the most important and versatile
methods in organic synthesis.3–5
Due to the importance of the biaryl motif as the back-
bone of ligands in asymmetric catalysis, highly function-
alized biaryl derivatives are very desirable targets.
Recently, we reported on the first modular synthesis of
atropisomeric C1-symmetric biaryl ligands by means of
highly regioselective bromine/lithium interconversions6
on polybrominated precursors.7,8 In the framework of
these studies we prepared a dissymmetrically substituted
Figure 1. X-ray structure of compound 2b.
biphenyl, 2,20-dibromo-6-methoxy-60-(trimethylsilyl)-
biphenyl (1),9 which allows a racemate resolution on
methylsilyl group migrated from one phenyl ring to
an early stage of the synthesis.
the methoxy-bearing phenyl ring (Scheme 1).
When dibromobiaryl 1 was subjected to two consecutive
In order to find out at which moment the silyl migration
halogen–metal permutations followed by trapping with
occurred, we treated 1 with just 1 equiv of butyllithium.
2 equiv of chlorodiphenylphosphine, not 2,20-bis(di-
Due to our previous investigations,6–8 we expected the
phenylphosphino)-substituted diphosphine 2a but its
bromine–lithium exchange to occur on the anisyl rather
regioisomer 2b was obtained, as confirmed by single-
than on the silylated ring. After trapping with chloro-
crystal X-ray analysis (Fig. 1).10,11 Apparently, the tri-
diphenylphosphine, we did not obtain monophosphine
3a but its regioisomer 3b (Scheme 2).12 Its structure
could be confirmed by single-crystal X-ray analysis
(Fig. 2).13 This result indicates that the silyl migration
*
occurred after the first bromine/lithium exchange on
the OMe-substituted phenyl ring.
Corresponding author. Tel.: +33 3 90 24 26 40; fax: +33 3 90 24 27
42; e-mail: frederic.leroux@ecpm.u-strasbg.fr
0040-4039/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.10.004

L. Bonnafoux et al. / Tetrahedron Letters 48 (2007) 8768–8772
8769
1) 2 eq. BuLi,
THF, 75 ºC
2) 2 eq. ClPPh2
H3CO Si(CH3)3
-
H3CO Si(CH3)3
BuLi, -75 ºC,
THF
THF,
75 ºC
-
Br
H3CO
H3CO Si(CH3)3
Li Br
Ph2P PPh2
5
H3CO Si(CH3)3
2a
Si
H3CO Li
Li
Br Br
THF,
-75 ºC
4
Br Br
1
1) 2 eq. BuLi,
THF,
H3CO PPh2
-
75 ºC
1
2) 2 eq. ClPPh2
(H3C)3Si Br
6
(H3C)3Si PPh2
79%
Scheme 3.
2b
Scheme 1.
complex 4 stabilizes then by migration of the silyl-group
affording intermediate 6.
1) 1 eq. BuLi,
THF,
-75 ºC
We wondered about the driving force for the selective
formation of intermediate 6. As we could show by intra-
molecular competition experiments, bromine stabilizes
an aryllithium carbanion in its meta-position more effec-
tively than a methoxy group. While the inductive and
mesomeric effects of the methoxy group can be neglected
(Hammett parameter rm = ꢀ0.12),17 all halogens have
not only the same sign but also virtually the same values
for the Hammett parameter rm (rm = +0.34 (F), +0.37
(Cl) and +0.39 (Br))17 and would thus favor a negative
partial charge at the meta-position. The influence of var-
ious substituents at the ortho-, meta-, and para-positions
of aryllithiums on their stability was shown by means of
competition and equilibration studies. Schlosser and
Maggi showed that a methoxy group located in the
para-position destabilizes an organometallic species.18
In contrast, when the methoxy group is moved from
the para- to the ortho-position it stabilizes an aryllithium
carbanion. However, in the meta-position its basicity
lowering effect was found to be almost invariant. Halo-
gen atoms have a different behavior as they are stabiliz-
ing in all three positions.19 Therefore, the aryllithium
intermediate 5 undergoes an intramolecular isomeriz-
ation toward its regioisomer 6, via the intermediate
formation of the silicate complex 4. Intermediate 6 is
thermodynamically more stable, that is, less basic, than
its counterpart 5 due to the better stabilization of the
aryllithium carbanion in the meta-position to the bro-
mine atom (6) relative to an aryllithium carbanion in
the meta-position to the methoxy group (5).
H3CO Si(CH3)3
2) 1 eq. ClPPh2
Ph2P Br
H3CO Si(CH3)3
3a
1) 1 eq. BuLi,
Br Br
H3CO PPh2
THF, -75 ºC
1
2) 1 eq. ClPPh2
84%
(H3C)3Si Br
3b
Scheme 2.
The striking migration of the silyl group can be
explained by the intermediate formation of a silicate-
complex 4 (Scheme 3). In fact, generally pentacoordi-
nated organosilicates are unstable, especially silicates
carrying only carbon14 or carbon and hydrogen14c,15 as
ligating atoms at silicon and have, with a few exceptions,
been described only recently.16 For this reason, the sili-
cate complex 4 is formed via an intramolecular attack of
the highly polar lithium–carbon bond of intermediate 5
(obtained after Br/Li-exchange on the OMe-substituted
phenyl ring) on the trimethylsilyl group. The silicate
In order to avoid the undesired silyl migration, we had
to avoid the intermediate silicate-complex formation.
Klumpp et al. showed14a that the stabilities of silicate
complexes like 4 depend on a large degree on the
strength of complexation of their counter ions by the
solvent. These authors were able to detect lithium 2,20-
biphenyldiyltrimethylsilicate in THF solution by 29Si
NMR. In THF, the lithium ion has an optimum com-
plexation by tetra-coordination.20 However, in diethyl
ether the thermodynamic stability of silicate complexes
is so low that they cannot be detected.
Aggregation plays an important role in organolithium
chemistry. Coordinating ligands—such as ethers—can
provide an alternative source of electron density for
Figure 2. X-ray structure of compound 3b.

8770
L. Bonnafoux et al. / Tetrahedron Letters 48 (2007) 8768–8772
X
the electron-deficient lithium atoms. Ethers can stabilize
aggregates by coordination to the lithium atoms and
then allow organolithiums to shift to an entropically
favored lower degree of aggregation.21 For example,
THF is a strong decoordinating solvent producing low
aggregation degrees albeit with an increase of basicity
and concomitantly an increase of nucleophilicity. The
latter could explain the formation of the silicate complex
4. Thus, in order to avoid the silyl migration, we had to
perform the bromine–lithium exchange in a non-coordi-
nating solvent and we have chosen toluene instead of
THF. In fact, toluene or generally hydrocarbon solu-
tions of organolithiums are invariably aggregated as
hexamers or tetramers. These solvents favor internal
stabilization of lithiated species.22 When 1 was consecu-
tively treated in toluene at ꢀ75 ꢁC with butyllithium,
chlorodiphenylphosphine, again butyllithium followed
by chlorodiphenylphosphine, diphosphine 2a was selec-
tively obtained via monophosphine 3a (Scheme 4).23
The structure of 2a could be confirmed by single-crystal
X-ray analysis (Fig. 3).24
X
BuLi, THF,
-75 ºC
X
H3C Si(CH3)3
(H3C)3Si CH3
X = OCH3
:
8a
2.3 : 1
: 1
8b 76%
X = F :
10a
0
10b 73%
(H3C)3Si Br
X
X = OCH3 : 8a, 91%
7 : X = OCH3
9 : X = F
BuLi, toluene,
0 ºC
(H3C)3Si CH3
Scheme 5.
isomer, compound 8a, could be detected. The outcome
of the reaction in THF is in perfect accordance with
the poor stabilization of an aryllithium carbanion in
the meta-position of a methoxy group.19 The stabilizing
effect was found to be almost the same as an unsubsti-
tuted phenyllithium. Thus, no significant extra-stabiliza-
tion is obtained when the carbanion is located at the
methoxy-substituted phenyl ring compared with the
unsubstituted phenyl ring and as a corollary, a mixture
of the two regioisomers is obtained.
In order to confirm our hypothesis, we subjected the
methoxy-substituted biphenyl 725 to the silyl migration
(Scheme 5). When 7 was treated at ꢀ75 ꢁC in THF with
1 equiv of butyllithium and subsequently trapped with
iodomethane, gas chromatographic analysis revealed
the presence of two isomeric compounds 8a and 8b in
a ration of 2.3:1.26 However, in toluene only one regio-
In contrast, the analogous experiment with a fluorinated
biphenyl (compound 9)27 afforded in THF exclusively
the silyl-migrated compound 10b.28 The outcome of
the reaction was again checked by gas chromatography
in comparison with authentic samples. The driving force
is the stabilization of the aryllithium carbanion in the
meta-position of the fluorine atom (Scheme 5).
In conclusion, we could show that trimethylsilyl-substi-
tuted biaryls undergo a migration of the silyl group after
lithiation involving the intermediate formation of a pen-
tacoordinated silicate complex. The driving force of this
silyl migration is the different relative basicity of the
aryllithium intermediates. The silyl migration can be
successfully avoided by changing the solvent from a
strongly coordinating solvent like THF to an apolar
non-coordinating solvent like toluene.
This stop-and-go isomerization (stop in toluene and go
in THF) can be useful in the synthesis of functionalized
biaryl scaffolds. For comparison, the basicity-gradient
driven halogen/migration in aromatic and heteroaro-
matic compounds became one major tool in the regio-
chemically exhaustive functionalization of these
compounds.3 In the present case, the silyl migration
can be exploited to allow the regiochemical synthesis
of biaryls. Subsequently, the trimethylsilyl group can
be either removed by protodesilylation (with acids,
bases, or fluoride ions in the presence of proton sources)
or converted into bromine or iodine atoms by halodesilyl-
ation (with molecular bromine, iodine, or iodmono-
chloride) for further functionalization.29,30
Figure 3. X-ray structure of compound 2a.
1) 1 eq. BuLi,
H3CO Si(CH3)3
-75 ºC, toluene
2) 1 eq. ClPPh2
86%
Ph2P Br
H3CO Si(CH3)3
3a
Br Br
1) 2 eq. BuLi,
-75 ºC, toluene
2) 2 eq. ClPPh2
H3CO Si(CH3)3
1
Acknowledgments
73%
Ph2P PPh2
This work was financially supported by the Bundesamt
fur Berufsbildung und Technologie (Bern) in the frame-
¨
2a
Scheme 4.
work of a KTI project (contract 5474.1 KTS) and the

L. Bonnafoux et al. / Tetrahedron Letters 48 (2007) 8768–8772
8771
(CDCl3, 101 MHz): d = 156.0, 141.3 (d, J = 14 Hz), 140.6
(d, J = 3 Hz), 137.9 (d, J = 15 Hz), 136.4 (d, J = 12 Hz),
133.7 (d, J = 20 Hz), 132.7, 132.6, 128.6 (d, J = 4 Hz),
128.5, 128.4, 127.9 (d, J = 7 Hz), 126.8 (d, J = 6 Hz),
126.4, 110.2, 54.2, 0.3. 31P NMR (CDCl3, 162 MHz):
d = –14.8 (s). Anal. Calcd for C28H28BrOPSi (521.65): C,
64.88; H 5.41. Found: C, 64.47; H, 5.50.
COST-D24 action WG0006-02. FRL is much indebted
to Professor M. Schlosser, Lausanne, for precious
advices.
References and notes
13. Crystal data for 3b: C28H28BrOPSi, Mr = 519.47, mono-
clinic, space group P21/n, a = 10.5223(6), b = 8.7751(5),
1. Wittig, G.; Pockels, U.; Dro¨ge, H. Ber. Dtsch. Chem. Ges.
1938, 71B, 1903–1912.
2. Gilman, H.; Langham, W.; Jacoby, A. L. J. Am. Chem.
Soc. 1939, 61, 106–109.
3. For review see: Schlosser, M. Angew. Chem. 2005, 117,
380; Angew. Chem., Int. Ed. 2005, 44, 376–393.
4. Leroux, F.; Schlosser, M.; Zohar, E.; Marek, I. In
Chemistry of Organolithium Compounds; Rappoport, Z.,
Ed.; Wiley: Chichester, 2004; Vol. 1, pp 435–493, and
literature cited therein.
5. Clayden, J. Organolithiums: Selectivity for Synthesis;
Pergamon: Oxford, 2002, pp 111–135 and literature cited
therein.
3
˚
˚
c = 27.669(3) A, b = 90.485(9)ꢁ, V = 2554.7(4) A , Z = 4,
q
calc = 1.351 g cmꢀ3
,
l = 1.737 mmꢀ1
,
F(000) = 1072,
crystal dimensions 0.28 · 0.11 · 0.09 mm, T = 140(2) K,
˚
Mo-Ka radiation, k = 0.71073 A, h = 2.75–25.03ꢁ, ꢀ12 6
h 6 12, ꢀ10 6 k 6 10, ꢀ31 6 l 6 30, 14,547 reflections
collected, 4288 independent reflections, Rint = 0.0732, R1
[I > 2r(I)] = 0.1210, wR2 (all data) = 0.3100, largest dif-
ference peak 1.629 e Aꢀ3, largest difference minimum
˚
ꢀ1.437 e Aꢀ3. CCDC 652948.
˚
14. (a) de Keijzer, A. H. J. F.; de Kanter, F. J. J.; Schakel, M.;
Schmitz, R. F.; Klumpp, G. W. Angew. Chem., Int. Ed.
1996, 35, 1127–1128; (b) de Keijzer, A. H. J. F.; de Kanter,
F. J. J.; Schakel, M.; Osinga, V. P.; Klumpp, G. W. J.
Organomet. Chem. 1997, 548, 29–32; (c) Rot, N.; Nijback-
er, T.; Kroon, R.; de Kanter, F. J. J.; Bickelhaupt, F.;
Lutz, M.; Spek, A. L. Organometallics 2000, 19, 1319–
1324.
6. Leroux, F.; Nicod, N.; Bonnafoux, L.; Quissac, B.;
Colobert, F. Lett. Org. Chem. 2006, 3, 165–169.
7. (a) Leroux, F.; Mettler, H. Adv. Synth. Catal. 2006, 349,
323–336; (b) Leroux, F.; Mettler, H. Synlett 2006, 766–
770.
15. (a) Hajdasz, D. J.; Squires, R. R. J. Am. Chem. Soc. 1986,
108, 3139–3140; (b) Hajdasz, D. J.; Ho, Y.; Squires, R. R.
J. Am. Chem. Soc. 1994, 116, 10751–10760; (c) Hong,
J.-H.; Boudjouk, P. Organometallics 1995, 14, 574–
576.
16. van Klink, G. M. P.; de Boer, H. J. R.; Schat, G.;
Akkerman, O. S.; Bickelhaupt, F.; Spek, A. L. Organo-
metallics 2002, 21, 2119–2135.
8. (a) Mettler, H.; Leroux, F.; Schlosser, M., WO 2006/
002729 (to Lonza AG, Switz., 20050606.); (b) Mettler, H.;
Leroux, F.; Schlosser, M., WO 2006/002730 (to Lonza
AG, Switz., 20050606.); Mettler, H.; Leroux, F.; Schlos-
ser, M., WO 2006/002731 (to Lonza AG, Switz.,
20050606.).
9. Trimethyl(6,20-dibromo-60-methoxy-biphenyl-2-yl)silane
(1). Mp 184–185 ꢁC. 1H NMR (CDCl3, 400 MHz):
d = 7.69 (dd, J = 8.0, 1.0 Hz, 1H), 7.60 (dd, J = 7.5,
1.0 Hz, 1H), 7.26 (m, 3H), 6.92 (dd, J = 9.0, 2.5 Hz, 1H),
3.74 (s, 3H), 0.23 (s, 9H). 13C NMR (CDCl3, 101 MHz):
d = 158.7, 144.0, 142.7, 134.1, 133.5, 132.5, 130.5, 129.0,
126.6, 125.9, 124.8, 109.9, 56.1, 0.1. Anal. Calcd for
C16H18Br2OSi (414.21): C, 46.39; H, 4.38. Found: C,
46.43; H, 4.41.
17. (a) Ritchie, C. D.; Sager, W. F. Progr. Phys. Org. Chem.
1964, 2, 323–400; (b) Hansch, C.; Leo, A.; Taft, R. W.
Chem. Rev. 1991, 91, 165–195.
18. Maggi, R.; Schlosser, M. Tetrahedron Lett. 1999, 40,
8797–8800.
´
´ ´
19. Kobylinska, J. PhD thesis, Ecole Polytechnique Federale
de Lausanne, 2004.
10. (20-Methoxy-60-(trimethylsilyl)biphenyl-2,6-diyl)bis(diphe-
nylphosphine) (2b). Mp 170–172 ꢁC. 1H NMR (CDCl3,
400 MHz): d = 7.3 (m, 7H), 7.2 (m, 18H), 6.25 (dd,
J = 6.7, 2.2 Hz, 1H), 2.49 (s, 3H), 0.04 (s, 9H). 13C NMR
(CDCl3, 101 MHz): d = 156.3 (t, J = 2 Hz), 151.5 (t,
J = 32 Hz), 140.9 (t, J = 2 Hz), 138.9 (t, J = 7 Hz), 138.4
(sym. m), 137.2 (sym. m), 133.7 (sym. m), 134.2 (sym. m),
128.3 (t, J = 3 Hz), 128.1, 127.9, 127.6 (sym. m), 127.2,
125.9, 109.1, 52.7, 0.5. 31P NMR (CDCl3, 162 MHz):
d = ꢀ17.3 (s). Anal. Calcd for C40H38OP2Si (624.78): C,
76.90; H, 6.13. Found: C, 76.68; H 5.94.
´
20. See: Setzer, W. N.; von Rague Schleyer, P. Adv. Organo-
met. Chem. 1985, 24, 353–451.
21. (a) Wakefield, B. J. The Chemistry of Organolithium
Compounds; Pergamon: Oxford, 1974; (b) West, P.;
Waack, R. J. Am. Chem. Soc. 1984, 67, 289–4399; (c)
Bergander, K.; He, R.; Chandrakumar, N.; Eppers, O.;
´
Gunther, H. Tetrahedron 1994, 51, 5861–5868; (d) Najera,
¨
C.; Yus, M.; Seebach, D. Helv. Chim. Acta 1984, 67, 289–
300; (e) Hoffmann, R. W.; Kemper, B. Tetrahedron Lett.
1981, 22, 5263–5266.
22. (a) Brown, T. L. Acc. Chem. Res. 1968, 1, 23–32; (b)
Williard, P. G. In Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Eds.; Pergamon: Oxford, 1990; Vol. 1,
11. Crystal data for 2b: C40H38OP2Si, Mr = 624.73, triclinic,
ꢀ
space group P1, a = 11.7325(4), b = 15.7258(6), c =
´
p 1; (c) von Rague Schleyer, P. Pure Appl. Chem. 1984, 56,
˚
19.6859(7) A,
a = 80.184(3),
b = 77.447(9),
c =
78.813(3)ꢁ, V = 3446.6(2) A , Z = 4, qcalc = 1.204 g cmꢀ3
,
3
151–162.
˚
23. 2,20-Bis-diphenylphosphanyl-6-methoxy-60-trimethylsilanyl-
biphenyl (2a). Mp 214–216 ꢁC. 1H NMR (CDCl3,
400 MHz): d = 7.59 (dd, J = 7.4, 1.6 Hz, 1H), 7.5 (m,
4H), 7.3 (m, 16H), 7.09 (ddd, J = 7.4, 3.5, 1.3 Hz, 1H),
7.04 (symm. m, 3H), 6.58 (d, J = 8.32 Hz, 1H), 3.08 (s,
3H), ꢀ0.36 (s, 9H). 13C NMR (CDCl3, 101 MHz):
d = 157.1 (d, J = 2 Hz), 144.1 (d, J = 8 Hz), 143.8 (d,
J = 8 Hz), 138.3, 137.4, 136.3 (d, J = 8 Hz), 136.1 (d,
J = 7 Hz), 134.5 (d, J = 2 Hz), 133.9 (dd, J = 20, 14 Hz),
133.3 (d, J = 19 Hz), 131.2 (dd, J = 6, 4 Hz), 128.8, 128.4,
128.2, 128.0, 127.9 (d, J = 2 Hz), 128.8, 127.6, 125.9 (d,
J = 2 Hz), 110.6, 54.7. 31P NMR (CDCl3, 162 MHz):
d = ꢀ12.2 (d, J = 38.1 Hz), ꢀ14.9 (d, J = 38.8 Hz). Anal.
l = 0.191 mmꢀ1
,
F(000) = 1320, crystal dimensions
0.20 · 0.16 · 0.12 mm, T = 140(2) K, Mo-Ka radiation,
˚
k = 0.71073 A, h = 2.90–25.03ꢁ, ꢀ13 6 h 6 12, ꢀ18 6
k 6 18, ꢀ23 6 l 6 23, 21,362 reflections collected, 10,694
independent reflections, Rint = 0.0388, R1 [I > 2r(I)] =
0.0507, wR2 (all data) = 0.1480, largest difference peꢀa3k
ꢀ3
˚
˚
0.577 e A , largest difference minimum ꢀ0.391 e A
.
CCDC 652949.
12. (6-Bromo-20-methoxy-60-(trimethylsilyl)biphenyl-2-yl)diphe-
nylphosphine (3b). Mp 133–135 ꢁC. 1H NMR (CDCl3,
400 MHz): d = 7.66 (dd, J = 7.7, 1.4 Hz, 1H), 7.38 (t,
J = 7.7 Hz, 1H), 7.3 (m, 7H), 7.2 (m, 6H), 6.63 (d,
J = 8.3 Hz, 1H), 3.03 (s, 3H), 0.05 (s, 9H). 13C NMR

8772
L. Bonnafoux et al. / Tetrahedron Letters 48 (2007) 8768–8772
Calcd for C40H38OP2Si (624.78): C, 76.90; H, 6.13. Found:
C, 76.59; H 6.02.
24. Crystal data for 2a: C40H38OP2Si, Mr = 624.73, mono-
0.2. Anal. Calcd for C17H22OSi (270.44): C, 75.50; H, 8.20.
Found: C, 75.62; H, 8.19.
27. (20-Bromo-6-fluorobiphenyl-2-yl)trimethylsilane (9). 1H
NMR (CDCl3, 300 MHz): d = 7.7 (d, J = 7.1 Hz, 1H),
7.52–7.51 (m, 1H), 7.5–7.3 (m, 3H), 7.26 (td, J = 7.7,
2.1 Hz, 1H), 7.17 (t, J = 9.2 Hz, 1H), 0.13 (s, 9H). 13C
NMR (CDCl3, 75 MHz): d = 159.4 (d, J = 247 Hz), 140.0
(d, J = 310 Hz), 134.2 (d, J = 15 Hz), 132.4, 132.1, 130.1
(d, J = 4 Hz), 129.7, 129.2 (d, J = 7 Hz), 126.8, 125.4 (d,
J = 1 Hz), 115.9 (d, J = 23 Hz), 0.1. Anal. Calcd for
C15H16BrFSi (323.27): C, 55.73; H, 4.99. Found: C, 55.95;
H, 5.09.
clinic, space group P21/n, a = 12.691(6), b = 17.561(6),
3
˚
˚
c = 15.685(6) A, b = 97.37(3)ꢁ, V = 3467(2) A , Z = 4,
q
calc = 1.197 g cmꢀ3
,
l = 0.190 mmꢀ1
,
F(000) = 1320,
crystal dimensions 0.18 · 0.16 · 0.13 mm, T = 140(2) K,
˚
Mo-Ka radiation, k = 0.71070 A, h = 3.03–27.64ꢁ,
ꢀ14 6 h 6 16, ꢀ22 6 k 6 22, ꢀ20 6 l 6 20, 27,538 reflec-
tions collected, 8029 independent reflections, Rint
=
0.0747, R1 [I > 2r(I)] = 0.0940, wR2 (all data) = 0.3398,
largest difference peak 0.329 e Aꢀ3, largest difference
˚
minimum ꢀ0.284 e Aꢀ3. CCDC 652950.
28. (60-Fluoro-20-methylbiphenyl-2-yl)-trimethylsilane (10b). 1H
NMR (CDCl3, 300 MHz): d = 7.7 (m, 1H), 7.35 (td,
J = 6.9, 1.7 Hz, 2H), 7.2–7.1 (m, 1H), 7.05 (dd, J = 7.3,
1.6 Hz, 1H), 6.99 (d, J = 7.6, 1H), 6.90 (t, J = 8.8 Hz, 1H),
1.97 (s, 3H), ꢀ0.05 (s, 9H). 13C NMR (CDCl3, 75 MHz):
d = 160.3 (d, J = 243 Hz), 140.9 (d, J = 1.6 Hz), 139.5 (d,
J = 3 Hz), 139.3 (d, J = 0.4 Hz), 135.0, 131.2 (d,
J = 18 Hz), 129.8, 129.1, 128.6 (d, J = 9 Hz), 127.0, 125.0
(d, J = 3 Hz), 112.7 (d, J = 23 Hz), 20.3 (d, J = 3 Hz),
ꢀ0.3. Anal. Calcd for C16H19FSi (258.4): C, 74.37; H, 7.41.
Found: C, 74.27; H, 7.33.
˚
25. (20-Bromo-6-methoxybiphenyl-2-yl)trimethylsilane (7). 1H
NMR (CDCl3, 300 MHz): d = 7.65 (dd, J = 8.6, 1.5 Hz,
1H), 7.5–7.3 (m, 2H), 7.3–7.2 (m, 3H), 7.02 (dd, J = 8.2,
0.9 Hz, 1H), 3.77 (s, 3H), 0.01 (s, 9H). 13C NMR (CDCl3,
75 MHz): d = 156.4, 140.7, 140.4, 136.1, 132.1, 132.1,
128.9, 128.6, 126.7, 126.6, 125.9, 111.6, 55.9, 0.14. Anal.
Calcd for C16H19BrOSi (335.31): C, 57.31; H, 5.71. Found:
C, 57.42; H, 5.53.
26. (6-Methoxy-20-methylbiphenyl-2-yl)trimethylsilane (8a).
1
Mp 51–53 ꢁC. H NMR (CDCl3, 300 MHz): d = 7.4–7.3
(m, 1H), 7.3–7.1 (m, 5H), 6.97 (dd, J = 8.1, 1.0 Hz, 1H),
3.61 (s, 3H), 1.96 (s, 3H), ꢀ0.13 (s, 9H). 13C NMR
(CDCl3, 75 MHz): d = 156.42, 140.6, 139.3, 137.6, 136.8,
130.7, 129.3, 127.9, 127.6, 126.9, 125.1, 111.4, 55.6, 20.0,
29. Heiss, C.; Leroux, F.; Schlosser, M. Eur. J. Org. Chem.
2005, 5242–5247.
30. Schlosser, M.; Heiss, C.; Leroux, F. Eur. J. Org. Chem.
2006, 735–737.