4-((2-halogeno-5-pyridyl)dimethylsilyl)phenylboronic acids: New potential building blocks for the synthesis of silicon-containing drugs

Article abstract of DOI:10.1021/om900175m

With the synthesis of 4-((2-fluoro-5-pyridyl)dimethylsilyl)phenylboronic acid (1a) and 4-((2-chloro-5-pyridyl)dimethylsilyl)phenylboronic acid (1b), new potential building blocks for the synthesis of siliconcontaining drugs have been made available. Compounds 1a,b were characterized by elemental analyses, multinuclear NMR experiments, and single-crystal X-ray diffraction studies. The synthetic potential of 1a was demonstrated by the Suzuki-Miyaura coupling reaction with 4-bromophenol to give (2-fluoro-5-pyridyl)(4'-hydroxy-(1,1'- biphenyl)-4-yl)dimethylsilane (2).

Full text of DOI:10.1021/om900175m

3218
Organometallics 2009, 28, 3218–3224
4-((2-Halogeno-5-pyridyl)dimethylsilyl)phenylboronic Acids: New
Potential Building Blocks for the Synthesis of Silicon-Containing
Drugs
Dennis Troegel, Frank Mo¨ller, Christian Burschka, and Reinhold Tacke*
Institut fu¨r Anorganische Chemie, UniVersita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany
ReceiVed March 5, 2009
With the synthesis of 4-((2-fluoro-5-pyridyl)dimethylsilyl)phenylboronic acid (1a) and 4-((2-chloro-
5-pyridyl)dimethylsilyl)phenylboronic acid (1b), new potential building blocks for the synthesis of silicon-
containing drugs have been made available. Compounds 1a,b were characterized by elemental analyses,
multinuclear NMR experiments, and single-crystal X-ray diffraction studies. The synthetic potential of
1a was demonstrated by the Suzuki-Miyaura coupling reaction with 4-bromophenol to give (2-fluoro-
5-pyridyl)(4′-hydroxy-(1,1′-biphenyl)-4-yl)dimethylsilane (2).
Boronic acids are extensively used as reagents in organic
are important building blocks in medicinal chemistry.10 Thus, 4-((2-
halogeno-5-pyridyl)silyl)phenylboronic acids are expected to be
challenging reagents for the synthesis of novel biologically active
organosilicon compounds. We report here on (i) the syntheses and
crystal structure analyses of compounds 1a,b and (ii) studies dealing
with a model Suzuki-Miyaura coupling reaction of 1a with
4-bromophenol to yield compound 2.
synthesis and thereby play an important role in the preparation
of drugs and agrochemicals.1 In this context, the palladium-
catalyzed cross-coupling reaction of aryl- or heteroarylboronic
acids with aryl- or heteroaryl halides or triflates (Suzuki-Miyaura
coupling) has proved to be an efficient method for C-C bond
formation.2 In addition, boronic acids and their derivatives have
many other applications: They can be used as catalysts,3 as
protecting groups for diols,4 and as receptors and sensors for
carbohydrates,5 and they are of interest as enzyme inhibitors,
BNCT agents, and drug release systems.6 In spite of this
importance of boronic acids, only a few examples of p-silyl-
substituted phenylboronic acids have been described in the
literature, mainly for applications in material sciences.7
In context with our systematic research on sila-substituted
drugs,8,9 we have now succeeded in synthesizing a series of novel
p-silyl-substituted phenylboronic acids that contain silicon-bound
2-halogeno-5-pyridyl groups. Generally, halogenopyridyl groups
* To whom correspondence should be addressed. Tel: +49-931-888-
5250. Fax: +49-931-888-4609 E-mail: r.tacke@mail.uni-wuerzburg.de.
(1) Hall, D. G. In Boronic Acids–Preparation and Applications in
Organic Synthesis and Medicine; Hall, D. G., Ed.; Wiley-VCH: Weinheim,
Germany, 2005; pp 1-99, and references therein.
(2) (a) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457–2483. (b)
Suzuki, A. In Metal-Catalyzed Cross-Coupling Reactions; Diederich, F.,
Stang, P. J., Eds.; Wiley-VCH: Weinheim, Germany, 1998; pp 49-97. (c)
Suzuki, A. J. Organomet. Chem. 2002, 653, 83–90. (d) Hassan, J.; Se´vignon,
M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem. ReV. 2002, 102, 1359–1469.
(e) Yin, L.; Liebscher, J. Chem. ReV. 2007, 107, 133–173.
(3) Ishihara, K.; Yamamoto, H. Eur. J. Org. Chem. 1999, 527–538.
(4) (a) Dahlhoff, W. V.; Ko¨ster, R. Synthesis 1980, 936–937. (b) Evans,
D. A.; Polniaszek, R. P. Tetrahedron Lett. 1986, 27, 5683–5686. (c) Gypser,
A.; Michel, D.; Nirschl, D. S.; Sharpless, K. B. J. Org. Chem. 1998, 63,
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1996, 108, 2038-2050; Angew. Chem., Int. Ed. Engl. 1996, 35, 1910-1922.
(b) Gray, C. W., Jr.; Houston, T. A. J. Org. Chem. 2002, 67, 5426–5428.
(6) (a) Yang, W.; Gao, X.; Wang, B. Med. Res. ReV. 2003, 23, 346–
368. (b) Paramore, A.; Frantz, S. Nature ReV. Drug DiscoVery 2003, 2,
611–612. (c) Ahmed, V.; Liu, Y.; Silvestro, C.; Taylor, S. D. Bioorg. Med.
Chem. 2006, 14, 8564–8573.
Results and Discussion
Syntheses of the Boronic Acids. The title compounds
1a,bwere prepared in multistep syntheses according to
Scheme 1. Thus, lithiation of the respective 5-bromo-2-
halopyridines with n-butyllithium in the presence of an excess
doifmethoxydimethylsilangeavthceeorrespondin(2g-halogeno-5-pyridyl)-
methoxydimethylsilanes 3a,b (yields: 3a, 52%; 3b, 60%).
Subsequent treatment of 3a,b with (4-bromophenyl)lithium
(obtained by lithiation of 1,4-dibromobenzene with n-
butyllithium) gave the (4-bromophenyl)(2-halogeno-5-py-
ridyl)dimethylsilanes 4a,b, respectively (yields: 4a, 74%; 4b,
71%). Metalation of 4a,b with tert-butyllithium and subse-
quent treatment with 4,4,5,5-tetramethyl-2-propyloxy-1,3,2-
dioxaborolane11 afforded the corresponding (2-halogeno-5-
(7) (a) Deng, X.; Mayeux, A.; Cai, C. J. Org. Chem. 2002, 67, 5279–
5283. (b) Fournier, J.-H.; Maris, T.; Wuest, J. D.; Guo, W.; Galoppini, E.
J. Am. Chem. Soc. 2003, 125, 1002–1006. (c) Deng, X.; Cai, C. Tetrahedron
Lett. 2003, 44, 815–817. (d) Kim, J.-U.; Lee, H.-B.; Shin, J.-S.; Kim, Y.-
H.; Joe, Y.-K.; Oh, H.-Y.; Park, C.-G.; Kwon, S.-K. Synth. Met. 2005, 150,
27–32. (e) You, Y.; An, C.-G.; Lee, D.-S.; Kim, J.-J.; Park, S. J. J. Mater.
Chem. 2006, 16, 4706–4713.
(8) Recent reviews dealing with silicon-based drugs: (a) Bains, W.;
Tacke, R. Curr. Opin. Drug DiscoVery DeV. 2003, 6, 526–543. (b) Showell,
G. A.; Mills, J. S. Drug DiscoVery Today 2003, 8, 551–556. (c) Mills, J. S.;
Showell, G. A. Expert Opin. InVestig. Drugs 2004, 13, 1149–1157. (d)
Sieburth, S. McN.; Chen, C.-A. Eur. J. Org. Chem. 2006, 311–322. (e)
Gately, R.; West, R. Drug DeV. Res. 2007, 68, 156–163. (f) Franz, A. K.
Curr. Opin. Drug DiscoVery DeV. 2007, 10, 654–671.
10.1021/om900175m CCC: $40.75
2009 American Chemical Society
Publication on Web 05/11/2009

4-((2-Halogeno-5-pyridyl)dimethylsilyl)phenylboronic Acids
Organometallics, Vol. 28, No. 11, 2009 3219
Scheme 1
Scheme 2
pyridyl)dimethyl(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
2-yl)phenyl)silanes 5a,b, respectively (yields: 5a, 57%; 5b,
80%). Finally, treatment of 5a,b with an aqueous solution
of sodium periodate12 and ammonium acetate yielded com-
pounds 1a (isolated as the solvate 1a · 0.5MeC(O)Me) and
1b, respectively (yields: 1a · 0.5MeC(O)Me, 75%; 1b, 75%).
Compounds 1a · 0.5MeC(O)Me, 1b, 4b, and 5a,b were
obtained as crystalline solids, whereas 3a,b and 4a were isolated
as liquids. The identities of all these compounds were established
by elemental analyses and multinuclear NMR spectroscopy. In
addition, compounds 1a · 0.5MeC(O)Me, 1b, 4b, and 5a were
structurally characterized by single-crystal X-ray diffraction.
Suzuki-Miyaura Cross-Coupling Reaction. The cross-
coupling reaction of 1a with 4-bromophenol in the presence of
tetrakis(triphenylphosphine)palladium(0)13 gave the corresponding
(9) Recent original publications dealing with sila-substituted drugs: (a)
Showell, G. A.; Barnes, M. J.; Daiss, J. O.; Mills, J. S.; Montana, J. G.;
Tacke, R.; Warneck, J. B. H. Bioorg. Med. Chem. Lett. 2006, 16, 2555–
2558. (b) Ilg, R.; Burschka, C.; Schepmann, D.; Wu¨nsch, B.; Tacke, R.
Organometallics 2006, 25, 5396–5408. (c) Bu¨ttner, M. W.; Burschka, C.;
Daiss, J. O.; Ivanova, D.; Rochel, N.; Kammerer, S.; Peluso-Iltis, C.; Bindler,
A.; Gaudon, C.; Germain, P.; Moras, D.; Gronemeyer, H.; Tacke, R.
ChemBioChem 2007, 8, 1688–1699. (d) Tacke, R.; Popp, F.; Mu¨ller, B.;
Theis, B.; Burschka, C.; Hamacher, A.; Kassack, M. U.; Schepmann, D.;
Wu¨nsch, B.; Jurva, U.; Wellner, E. ChemMedChem 2008, 3, 152–164. (e)
Warneck, J. B.; Cheng, F. H. M.; Barnes, M. J.; Mills, J. S.; Montana,
J. G.; Naylor, R. J.; Ngan, M.-P.; Wai, M.-K.; Daiss, J. O.; Tacke, R.;
Rudd, J. A. Toxicol. Appl. Pharmacol. 2008, 232, 369–375.
(10) (a) Denton, T. T.; Zhang, X.; Cashman, J. R. J. Med. Chem. 2005,
48, 224–239. (b) Hocke, C.; Prante, O.; Lo¨ber, S.; Hu¨bner, H.; Gmeiner,
P.; Kuwert, T. Bioorg. Med. Chem. Lett. 2005, 15, 4819–4823. (c) Wiles,
J. A.; Song, Y.; Wang, Q.; Lucien, E.; Hashimoto, A.; Cheng, J.; Marlor,
C. W.; Ou, Y.; Podos, S. D.; Thanassi, J. A.; Thoma, C. L.; Deshpande,
M.; Pucci, M. J.; Bradbury, B. J. Bioorg. Med. Chem. Lett. 2006, 16, 1277–
1281. (d) Kahn, M. G. C.; Konde, E.; Dossou, F.; Labaree, D. C.; Hochberg,
R. B.; Hoyte, R. M. Bioorg. Med. Chem. Lett. 2006, 16, 3454–3458. (e)
Johns, B. A.; Gudmundsson, K. S.; Allen, S. H. Bioorg. Med. Chem. Lett.
2007, 17, 2858–2862. (f) Gao, Y.; Horti, A. G.; Kuwabara, H.; Ravert,
H. T.; Hilton, J.; Holt, D. P.; Kumar, A.; Alexander, M.; Endres, C. J.;
Wong, D. F.; Dannals, R. F. J. Med. Chem. 2007, 50, 3814–3824.
(11) Andersen, M. W.; Hildebrandt, B.; Ko¨ster, G.; Hoffmann, R. W.
Chem. Ber. 1989, 122, 1777–1782.
1,1′-biphenyl-4-ol derivative 2 in 45% yield (Scheme 2). In
addition, the formation of a related coupling product, the 1,1′-
biphenyl derivative 6 (55% yield), was observed (Scheme 2). The
low yield of 2 is similar to those observed for comparable coupling
reaction products obtained from 4-bromophenol.13a
Compounds 2 and 6 were isolated as colorless crystalline
solids. Their identities were established by elemental analyses
and NMR spectroscopy, and 2 was additionally characterized
by single-crystal X-ray diffraction.
Crystal Structure Analyses. Compounds 1a · 0.5MeC(O)Me,
1b, 2, 4b, and 5a were structurally characterized by single-
crystal X-ray diffraction. The crystal data and the experimental
parameters used for these studies are given in Table 1. The
molecular structures of 1a and 2 are depicted in Figures 1 and
(12) (a) Coutts, S. J.; Adams, J.; Krolikowski, D.; Snow, R. J.
Tetrahedron Lett. 1994, 35, 5109–5112. (b) Falck, J. R.; Bondlela, M.;
Venkataraman, S. K.; Srinivas, D. J. Org. Chem. 2001, 66, 7148–7150.
(13) (a) Edsall, R. J.; Harris, H. A.; Manas, E. S.; Mewshaw, R. E.
Bioorg. Med. Chem. 2003, 11, 3457–3474. (b) Mewshaw, R. E.; Edsall,
R. J., Jr.; Yang, C.; Manas, E. S.; Xu, Z. B.; Henderson, R. A.; Keith,
J. C., Jr.; Harris, H. A. J. Med. Chem. 2005, 48, 3953–3979.

3220 Organometallics, Vol. 28, No. 11, 2009
Troegel et al.
Table 1. Crystal Data and Experimental Parameters for the Crystal Structure Analyses of 1a · 0.5MeC(O)Me, 1b, 2, 4b, and 5a
1a · 0.5MeC(O)Me
1b
2
4b
5a
empirical formula
formula mass, g mol-1
collection T, K
λ(Mo KR), Å
cryst syst
space group (No.)
a, Å
b, Å
C14.5H18BFNO2.5Si C13H15BClNO2Si
C19H18FNOSi
323.43
193(2)
0.710 73
orthorhombic
Pbcn (60)
15.218(3)
9.2640(10)
24.984(3)
90
90
90
3522.3(9)
8
1.220
C13H13BrClNSi
326.69
100(2)
C19H25BFNO2Si
357.30
193(2)
0.710 73
monoclinic
P21/c (14)
12.0086(15)
12.2203(14)
13.4878(18)
90
92.594(16)
90
1977.3(4)
4
1.200
0.139
304.20
193(2)
291.61
100(2)
0.710 73
monoclinic
P21/n (14)
6.6964(10)
22.190(3)
11.1528(17)
90
0.710 73
monoclinic
C2/c (15)
20.5093(8)
15.6888(6)
9.7982(4)
90
0.710 73
triclinic
j
P1 (2)
6.2696(13)
9.6147(19)
12.194(2)
95.37(3)
100.82(3)
98.07(3)
709.4(2)
2
c, Å
R, deg
ꢀ, deg
97.817(18)
90
105.419(2)
90
γ, deg
V, Å3
1641.8(4)
4
3039.3(2)
8
Z
D(calcd), g cm-3
1.231
1.275
1.529
3.148
328
µ, mm-1
0.158
0.326
0.146
1360
F(000)
640
1216
760
cryst dimens, mm
2θ range, deg
index ranges
0.5 × 0.4 × 0.2
5.20-58.12
-9 e h e 9
-30 e k e 30
-15 e l e 15
23 419
0.230 × 0.095 × 0.047 0.5 × 0.4 × 0.2 0.403 × 0.258 × 0.192 0.5 × 0.3 × 0.1
3.32-66.82
-30 e h e 31
-24 e k e 24
-15 e l e 15
48 634
5.36-58.22
-20 e h e 20
-12 e k e 12
-34 e l e 34
48 816
3.42-65.88
-9 e h e 9
-14 e k e 14
-18 e l e 18
41 227
5.56-58.22
-16 e h e 16
-16 e k e 16
-18 e l e 18
20 682
no. of collected rflns
no. of indep rflns
Rint
4240
0.0371
5811
4704
5247
5269
0.0566
0.0410
0.0488
0.0498
no. of rflns used
no. of restraints
no. of params
Sa
4240
9
207
1.037
0.0737/0.4762
0.0441
0.1274
5811
0
180
1.045
0.0480/2.3900
0.0379
0.1058
4704
0
214
1.066
0.0654/0.7362
0.0410
0.1198
5247
6
163
1.045
0.0342/0.1475
0.0239
0.0659
5269
14
304
1.052
0.0681/0.1642
0.0455
0.1276
weight params a/bb
R1c (I > 2σ(I))
wR2d (all data)
max/min residual electron density, e Å-3 +0.335/-0.384
+0.622/-0.385
+0.329/-0.374 +0.754/-0.375
+0.328/- 0.314
a
b
2
2
2
S ) {∑[w(Fo - Fc2)2]/(n - p)}0.5; n ) no. of reflections; p ) no. of parameters. w-1 ) σ2(Fo ) + (aP)2 + bP, with P ) [max(Fo ,0) + 2Fc2]/3.
c R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo )2]}0.5
.
d
2
2
Figure 1. Molecular structure of 1a in the crystal of
1a · 0.5MeC(O)Me (probability level of displacement ellipsoids
50%). Selected bond distances (Å), bond angles (deg), and torsion
angles (deg): Si-C1 ) 1.8804(14), Si-C7 ) 1.8894(16), Si-C12
) 1.8615(17), Si-C13 ) 1.8711(17), O1-B ) 1.364(2), O2-B
) 1.352(2), C4-B ) 1.580(2); C1-Si-C7 ) 104.57(6), C1-
Si-C12 ) 110.45(7), C1-Si-C13 ) 109.40(7), C7-Si-C12 )
110.36(8), C7-Si-C13 ) 109.97(8), C12-Si-C13 ) 111.84(8),
O1-B-O2 ) 119.96(14), O1-B-C4 ) 123.09(14), O2-B-C4
) 116.95(15); O1-B-C4-C3 ) -30.5(2), O1-B-C4-C5 )
149.20(16), O2-B-C4-C3 ) 149.98(16), O2-B-C4-C5 )
-30.3(2).
Figure 2. Molecular structure of 2 in the crystal (probability level
of displacement ellipsoids 50%). Selected bond distances (Å), bond
angles (deg), and torsion angles (deg): Si-C1 ) 1.8649(17), Si-C2
) 1.8722(18), Si-C3 ) 1.8849(13), Si-C8 ) 1.8776(13), O-C17
) 1.3670(15), C11-C14 ) 1.4857(16); C1-Si-C2 ) 110.17(10),
C1-Si-C3 ) 109.14(7), C1-Si-C8 ) 110.61(7), C2-Si-C3 )
109.40(7), C2-Si-C8 ) 108.89(7), C3-Si-C8 ) 108.60(6);
C10-C11-C14-C15 ) 33.50(18), C10-C11-C14-C19 )
-144.28(13), C12-C11-C14-C15 ) -148.37(12), C12-C11-
C14-C19 ) 33.85(18). Intermolecular O-H · · · N hydrogen bonds
lead to the formation of infinite chains in the crystal of 2. Distances
(Å) and angles (deg) of the hydrogen-bonding system:14 O-H )
0.886(19), H · · · N ) 2.021(19), O · · · N ) 2.8855(17); O-H · · · N
) 165.0(19).
2; selected interatomic distances, bond angles, and torsion angles
are given in the respective figure legends (for further details of
the crystal structure analyses, see the Supporting Information).
The crystal structures of 1a · 0.5MeC(O)Me, 1b, 2, 4b, and
5a (Figures 1 and 2 and the Supporting Information) do not
show any special features and therefore do not need a detailed
discussion, except for the hydrogen-bonding systems observed
for 1a · 0.5MeC(O)Me and 1b. In both cases, intermolecular
O-H · · · O hydrogen bonds lead to the formation of centrosym-
metric dimers of the boronic acid, which are further connected
by intermolecular O-H · · · N hydrogen bonds, resulting in a
(14) The hydrogen-bonding systems were analyzed by using the program
system PLATON: (a) Spek, A. L., PLATON; University of Utrecht, Utrecht,
The Netherlands, 1998. (b) Spek, A. L. Acta Crystallogr., Sect. A 1990, 46
(Supplement), C34.

4-((2-Halogeno-5-pyridyl)dimethylsilyl)phenylboronic Acids
Organometallics, Vol. 28, No. 11, 2009 3221
Figure 3. Two-dimensional hydrogen-bonding network in the crystal of 1a · 0.5MeC(O)Me. The dashed lines indicate intermolecular O-H · · · O
and O-H · · · N hydrogen bonds, respectively, leading to the formation of centrosymmetric dimeric units of the boronic acid, which are
further connected to form a corrugated layer structure. The acetone molecules and the hydrogen atoms (except for the OH atoms) are
omitted for clarity. Distances (Å) and angles (deg) of the hydrogen-bonding system:14 O1-H1 ) 0.83(3), H1 · · · NB ) 2.00(3), O1 · · · NB
) 2.820(2), O1-H1 · · · NB ) 174(2); O2-H2 ) 0.80(3), H2 · · · O1A ) 1.97(3), O2 · · · O1A ) 2.7628(18), O2-H2 · · · O1A ) 174(3).
external CFCl3 (19F, δ 0; CDCl3, [D6]DMSO), or external TMS
corrugated layer structure. This is shown exemplarily for
(29Si, δ 0; CDCl3, [D6]DMSO). Analysis and assignment of the 1H
1a · 0.5MeC(O)Me in Figure 3.
1
NMR data were supported by H,1H COSY, 13C,1H HMQC, and
13C,1H HMBC experiments. Assignment of the 13C NMR data was
Conclusions
supported by DEPT 135, 13C,1H HMQC, and 13C,1H HMBC
With the syntheses of the 4-((2-halogeno-5-pyridyl)dimeth-
ylsilyl)phenylboronic acids 1a,b, two new silicon-containing
boronic acids have been made accessible. Compounds 1a,b were
prepared in four-step syntheses, starting from the corresponding
5-bromo-2-halogenopyridine. The key step in the synthesis of
1a,b is the low-temperature coupling reaction of dimethoxy-
dimethylsilane with a (2-halogeno-5-pyridyl)lithium reagent,
generated in situ from the respective 5-bromo-2-halopyridine
and n-butyllithium in diethyl ether. Owing to their synthetically
valuable boronic acid functionality and their 2-halogeno-5-
pyridyl group, compounds 1a,b are promising building blocks
for the synthesis of new silicon-based drugs. The synthetic
potential of 1a has been exemplarily demonstrated by the
Suzuki-Miyaura cross-coupling reaction with 4-bromophenol
to give the (1,1′-biphenyl-4-yl)(2-halogeno-5-pyridyl)dimeth-
ylsilanes 2 and 6.
experiments.
Preparation of 4-((2-Fluoro-5-pyridyl)dimethylsilyl)phenyl-
boronic Acid-Hemiacetone (1a · 0.5MeC(O)Me). A solution of
sodium periodate (7.20 g, 33.7 mmol) and ammonium acetate (2.60
g, 33.7 mmol) in water (300 mL) was added in a single portion at
20 °C to a stirred solution of 5a (3.00 g, 8.40 mmol) in acetone
(420 mL), and the resulting mixture was then stirred at 20 °C for
6 days. The organic solvent was removed under reduced pressure,
and the aqueous solution was adjusted to pH 3 with 2 M
hydrochloric acid. Ethyl acetate (400 mL) was added, the organic
layer was separated, and the aqueous phase was extracted with ethyl
acetate (2 × 400 mL). The organic extracts were combined, the
solvent was removed under reduced pressure, and the residue was
purified by column chromatography on silica gel (silica gel, 32-63
µm (ICN 02826); eluent, n-hexane/acetone (2:1 (v/v))) to afford a
yellowish oily product, which was crystallized from n-hexane/
acetone/water (30:10:1 (v/v/v)) (82 mL; crystallization at 20 °C
over a period of 8 days by slow evaporation of the solvent). The
precipitate was isolated by filtration, washed with n-hexane (3 ×
10 mL), and dried in vacuo (0.05 mbar, 20 °C, 6 h) to give
1a · 0.5MeC(O)Me in 75% yield as a colorless crystalline solid (1.92
g, 6.31 mmol); mp 73-74 °C. 1H NMR (500.1 MHz, [D6]DMSO):
δ 0.57 (s, 6 H, SiCH3), 2.07 (s, 3 H, CCH3, CH3C(O)CH3),
7.14-7.16 (m, 1 H, H-3, C5H3N), 7.48-7.53 (m, 2 H, H-3/H-5,
C6H4), 7.77-7.86 (m, 2 H, H-2/H-6, C6H4), 8.01-8.05 (m, 1 H,
H-4, C5H3N), 8.1 (br. s, 2 H, BOH), 8.29-8.30 (m, 1 H, H-6,
C5H3N). 13C NMR (125.8 MHz, [D6]DMSO): δ -3.0 (SiCH3), 30.7
Experimental Section
General Procedures. All syntheses were carried out under dry
nitrogen. The organic solvents used were dried and purified
according to standard procedures and stored under dry nitrogen. A
Bu¨chi GKR-51 apparatus was used for the bulb-to-bulb distillations.
Melting points were determined with a Bu¨chi B-540 melting point
1
apparatus using samples in sealed glass capillaries. The H, 13C,
11B, 19F, and 29Si NMR spectra were recorded at 23 °C on a Bruker
DRX-300 (1H, 300.1 MHz; 13C, 75.5 MHz; 29Si, 59.6 MHz), Bruker
Avance 400 (1H, 400.1 MHz; 13C, 100.6 MHz; 19F, 376.5 MHz;
29Si, 79.5 MHz), or Bruker Avance 500 NMR spectrometer (1H,
500.1 MHz; 13C, 125.8 MHz; 11B, 160.5 MHz; 29Si, 99.4 MHz).
CDCl3 or [D6]DMSO was used as the solvent. Chemical shifts
(ppm) were determined relative to internal CHCl3 (1H, δ 7.24;
CDCl3), internal CDCl3 (13C, δ 77.0; CDCl3), internal [D5]DMSO
(1H, δ 2.49; [D6]DMSO), internal [D6]DMSO (13C, δ 39.5;
[D6]DMSO), external BF3 · Et2O (11B, δ 0; CDCl3, [D6]DMSO),
2
(CCH3, CH3C(O)CH3), 109.3 (d, JCF ) 35.2 Hz, C-3, C5H3N),
131.0 (d, 4JCF ) 4.6 Hz, C-5, C5H3N), 132.8 (C-3/C-5, C6H4), 133.5
(C-2/C-6, C6H4), 138.5 (C-1, C6H4), 147.6 (d, 3JCF ) 7.5 Hz, C-4,
3
1
C5H3N), 152.5 (d, JCF ) 13.7 Hz, C-6, C5H3N), 164.0 (d, JCF
)
236.9 Hz, C-2, C5H3N), 206.4 (CdO, CH3C(O)CH3), BC not
detected. 11B NMR (160.5 MHz, [D6]DMSO): δ 27.2. 19F NMR
(376.5 MHz, [D6]DMSO): δ -67.6. 29Si NMR (99.4 MHz,
5
[D6]DMSO): δ -8.5 (d, JSiF ) 1.8 Hz). Anal. Calcd for

3222 Organometallics, Vol. 28, No. 11, 2009
Troegel et al.
C13H15BFNO2Si · 0.5C3H6O: C, 57.25; H, 5.96; N, 4.60. Found: C,
57.08; H, 5.82; N, 4.66.
removed under reduced pressure to give 2 in 45% yield as a
colorless solid (145 mg, 448 µmol); mp 132-133 °C. H NMR
1
(500.1 MHz, CDCl3): δ 0.60 (s, 6 H, SiCH3), 6.2 (br. s, 1 H, OH),
6.90-6.94 (m, 3 H, H-3, C5H3N, H-3′/H-5′, C6H4OH), 7.44-7.47
(m, 2 H, H-2′/H-6′, C6H4OH), 7.51-7.55 (m, 4 H, H-2/H-3/H-5/
H-6, SiC6H4), 7.87-7.91 (m, 1 H, H-4, C5H3N), 8.31-8.32 (m, 1
H, H-6, C5H3N). 13C NMR (125.8 MHz, CDCl3): δ -2.5 (SiCH3),
109.4 (d, 2JCF ) 34.1 Hz, C-3, C5H3N), 115.8 (C-3′/C-5′, C6H4OH),
126.3 (C-2/C-6, SiC6H4), 128.3 (C-2′/C-6′, C6H4OH), 131.1 (d, 4JCF
Preparation of 4-((2-Chloro-5-pyridyl)dimethylsilyl)phenyl-
boronic Acid (1b). A solution of sodium periodate (13.7 g, 64.1
mmol) and ammonium acetate (5.00 g, 64.9 mmol) in water (600
mL) was added in a single portion at 20 °C to a stirred solution of
5b (6.00 g, 16.1 mmol) in acetone (840 mL), and the resulting
mixture was then stirred at 20 °C for 10 days. The organic solvent
was removed under reduced pressure, and the aqueous solution was
adjusted to pH 3 with 2 M hydrochloric acid. Ethyl acetate (600
mL) was added, the organic layer was separated, and the aqueous
phase was extracted with ethyl acetate (2 × 600 mL). The organic
extracts were combined, the solvent was removed under reduced
pressure, and the residue was purified by column chromatography
on silica gel (silica gel, 32-63 µm (ICN 02826); eluent, n-hexane/
acetone (2:1 (v/v))) to afford a solid product, which was recrystal-
lized from n-hexane/acetone/water (700:300:1 (v/v/v)) (100 mL;
crystallization at 20 °C over a period of 10 days by slow evaporation
of the solvent). The precipitate was isolated by filtration, washed
with n-hexane (2 × 10 mL), and dried in vacuo (0.05 mbar, 20 °C,
3 h) to give 1b in 75% yield as a colorless crystalline solid (3.49
g, 12.0 mmol); mp 185-186 °C. 1H NMR (500.1 MHz, [D6]DMSO):
δ 0.57 (s, 6 H, SiCH3), 7.47-7.53 (m, 3 H, H-3/H-5, C6H4, H-3,
C5H3N), 7.77-7.86 (m, 2 H, H-2/H-6, C6H4), 7.88 (dd, 3JHH ) 8.0
) 4.8 Hz, C-5, C5H3N), 133.1 (C-4, SiC6H4), 134.1 (C-1′, C6H4OH),
3
134.5 (C-3/C-5, SiC6H4), 142.1 (C-1, SiC6H4), 147.3 (d, JCF
)
7.5 Hz, C-4, C5H3N), 152.7 (d, 3JCF ) 12.6 Hz, C-6, C5H3N), 155.8
(C-4′, C6H4OH), 164.5 (d, 1JCF ) 242.1 Hz, C-2, C5H3N). 19F NMR
(376.5 MHz, CDCl3): δ -67.5. 29Si NMR (99.4 MHz, CDCl3): δ
-8.2 (d, 5JSiF ) 1.8 Hz). Anal. Calcd for C19H18FNOSi: C, 70.56;
H, 5.61; N, 4.33. Found: C, 70.22; H, 5.68; N, 4.11.
Preparation of (2-Fluoro-5-pyridyl)methoxydimethylsilane
(3a). A 2.5 M solution of n-butyllithium in hexanes (28.4 mL, 71.0
mmol of n-BuLi) was added dropwise at -70 °C ((5 °C,
temperature measurement within the flask) within 3 h to a stirred
mixture of dimethoxydimethylsilane (12.8 g, 106 mmol), 5-bromo-
2-fluoropyridine (12.5 g, 71.0 mmol), and diethyl ether (120 mL)
(the n-butyllithium solution was added via a special horizontally
elongated side neck of the three-necked flask, which itself was
immersed in the cooling bath to ensure precooling of the n-
butyllithium solution before making contact with the reaction
mixture). After the addition was complete, the resulting mixture
was stirred at -75 °C for 5 h and then warmed to 20 °C within
17 h. The precipitate was removed by filtration, washed with diethyl
ether (2 × 20 mL), and discarded. The filtrate and washings were
combined, the solvent was removed under reduced pressure, and
the residue was purified by fractional distillation to give 3a in 52%
yield as a colorless liquid (6.87 g, 37.1 mmol); bp 96 °C/10 mbar.
1H NMR (400.1 MHz, CDCl3): δ 0.36 (s, 6 H, SiCH3), 3.41 (s, 3
H, OCH3), 6.89-6.92 (m, 1 H, H-3, C5H3N), 7.87-7.92 (m, 1 H,
H-4, C5H3N), 8.29-8.30 (m, 1 H, H-6, C5H3N). 13C NMR (75.5
MHz, CDCl3): δ -2.3 (SiCH3), 50.6 (OCH3), 109.3 (d, 2JCF ) 34.9
Hz, C-3, C5H3N), 129.9 (d, 4JCF ) 4.7 Hz, C-5, C5H3N), 146.3 (d,
3JCF ) 7.3 Hz, C-4, C5H3N), 152.5 (d, 3JCF ) 13.4 Hz, C-6, C5H3N),
4
Hz, JHH ) 2.1 Hz, 1 H, H-4, C5H3N), 8.1 (br s, 2 H, BOH), 8.45
4
5
(dd, JHH ) 2.1 Hz, JHH ) 0.7 Hz, 1 H, H-6, C5H3N). 13C NMR
(125.6 MHz, [D6]DMSO): δ -3.1 (SiCH3), 123.9 (C-3, C5H3N),
132.4 (C-5, C5H3N), 132.9 (C-3/C-5, C6H4), 133.5 (C-2/C-6, C6H4),
138.2 (C-1, C6H4), 145.1 (C-4, C5H3N), 151.6 (C-2, C5H3N), 154.4
(C-6, C5H3N), BC not detected. 11B NMR (160.5 MHz, [D6]DMSO):
δ 27.6. 29Si NMR (99.4 MHz, [D6]DMSO): δ -8.3. Anal. Calcd
for C13H15BClNO2Si: C, 53.54; H, 5.18; N, 4.80. Found: C, 53.51;
H, 5.10; N, 4.80.
Preparation of (2-Fluoro-5-pyridyl)(4′-hydroxy-(1,1′-biphe-
nyl)-4-yl)dimethylsilane (2) and ((1,1′-Biphenyl)-4-yl)(2-fluoro-
5-pyridyl)dimethylsilane (6). A 2 M aqueous solution of sodium
carbonate (1.7 mL) was added to
a
suspension of
1a · 0.5CH3C(O)CH3 (300 mg, 986 µmol), 4-bromophenol (358 mg,
2.07 mmol), and tetrakis(triphenylphosphine)palladium(0) (72.0 mg,
62.3 µmol) in 1,2-dimethoxyethane (5 mL), and the resulting
mixture was heated under reflux for 23 h. Ethyl acetate (25 mL)
and 2 M hydrochloric acid (25 mL) were added, the organic layer
was separated, and the aqueous phase was extracted with ethyl
acetate (3 × 25 mL). The organic extracts were combined and dried
over anhydrous sodium sulfate, the solvent was removed under
reduced pressure, and the residue was purified by column chro-
matography on silica gel (silica gel, 32-63 µm (ICN 02826); eluent,
n-hexane/ethyl acetate (2:1 (v/v))). The relevant first fractions (GC
control) were combined, and the solvent was removed under
reduced pressure to give 6 in 55% yield as a colorless solid (166
1
164.8 (d, JCF ) 241.2 Hz, C-2, C5H3N). 19F NMR (376.5 MHz,
CDCl3): δ -66.1. 29Si NMR (59.6 MHz, CDCl3): δ 9.0 (d, 5JSiF
)
1.8 Hz). Anal. Calcd for C8H12FNOSi: C, 51.86; H, 6.53; N, 7.56.
Found: C, 51.47; H, 6.40; N, 7.99.
Preparation of (2-Chloro-5-pyridyl)methoxydimethylsilane
(3b). A 2.5 M solution of n-butyllithium in hexanes (30 mL, 75.0
mmol of n-BuLi) was added dropwise at -70 °C ((5 °C,
temperature measurement within the flask) within 2 h to a stirred
mixture of dimethoxydimethylsilane (10.2 g, 84.8 mmol), 5-bromo-
2-chloropyridine (10.9 g, 56.6 mmol), and diethyl ether (130 mL)
(the n-butyllithium solution was added via a special horizontally
elongated side neck of the three-necked flask, which itself was
immersed in the cooling bath to ensure precooling of the n-
butyllithium solution before making contact with the reaction
mixture). After the addition was complete, the mixture was stirred
at -70 °C for 5 h and then warmed to 20 °C within 15 h. The
precipitate was removed by filtration, washed with diethyl ether (5
× 20 mL), and discarded. The filtrate and washings were combined,
the solvent was removed under reduced pressure, and the residue
was purified by bulb-to-bulb distillation (80-85 °C/0.09 mbar) to
give 3b in 60% yield as a colorless liquid (6.86 g, 34.0 mmol). 1H
NMR (500.1 MHz, CDCl3): δ 0.35 (s, 6 H, SiCH3), 3.40 (s, 3 H,
OCH3), 7.28 (dd, 3JHH ) 7.9 Hz, 5JHH ) 0.9 Hz, 1 H, H-3, C5H3N),
1
mg, 540 µmol); mp 81-82 °C. H NMR (500.1 MHz, CDCl3): δ
0.61 (s, 6 H, SiCH3), 6.91-6.92 (m, 1 H, H-3, C5H3N), 7.34-7.37
(m, 1 H, H-4′, C6H5), 7.42-7.46 (m, 2 H, H-3′/H-5′, C6H5),
7.56-7.61 (m, 6 H, H-2/H-3/H-5/H-6, SiC6H4, H-2′/H-6′, C6H5),
7.85-7.89 (m, 1 H, H-4, C5H3N), 8.33-8.34 (m, 1 H, H-6, C5H3N).
13C NMR (125.8 MHz, CDCl3): δ -2.5 (SiCH3), 109.3 (d, 2JCF
)
35.2 Hz, C-3, C5H3N), 126.8 (C-2/C-6, SiC6H4), 127.1 (C-2′/C-6′,
4
C6H5), 127.6 (C-4′, C6H5), 128.8 (C-3′/C-5′, C6H5), 130.7 (d, JCF
) 4.6 Hz, C-5, C5H3N), 134.5 (C-3/C-5, SiC6H4), 135.2 (C-4,
SiC6H4), 140.7 (C-1′, C6H5), 142.4 (C-1, SiC6H4), 146.9 (d, 3JCF
)
7.0 Hz, C-4, C5H3N), 153.0 (d, 3JCF ) 10.5 Hz, C-6, C5H3N), 164.6
(d, 1JCF ) 242.1 Hz, C-2, C5H3N). 19F NMR (376.5 MHz, CDCl3):
5
δ -66.9. 29Si NMR (99.4 MHz, CDCl3): δ -8.2 (d, JSiF ) 1.8
3
4
7.73 (dd, JHH ) 7.9 Hz, JHH ) 2.0 Hz, 1 H, H-4, C5H3N), 8.44
(dd, JHH ) 2.0 Hz, JHH ) 0.9 Hz, 1 H, H-6, C5H3N). 13C NMR
(125.8 MHz, CDCl3): δ -2.3 (SiCH3), 50.7 (OCH3), 123.9 (C-3,
C5H3N), 131.1 (C-5, C5H3N), 143.7 (C-4, C5H3N), 153.0 (C-2,
C5H3N), 154.0 (C-6, C5H3N). 29Si NMR (99.4 MHz, CDCl3): δ
4
5
Hz). Anal. Calcd for C19H18FNSi: C, 74.23; H, 5.90; N, 4.56. Found:
C, 74.10; H, 5.96; N, 4.66.
Upon further elution with n-hexane/ethyl acetate (2:1 (v/v)), the
relevant fractions (GC control) were combined, and the solvent was

4-((2-Halogeno-5-pyridyl)dimethylsilyl)phenylboronic Acids
Organometallics, Vol. 28, No. 11, 2009 3223
8.8. Anal. Calcd for C8H12ClNOSi: C, 47.63; H, 6.00; N, 6.94.
Found: C, 47.87; H, 5.93; N, 7.34.
the organic layer was separated, and the aqueous phase was
extracted with diethyl ether (3 × 400 mL). The organic extracts
were combined and dried over anhydrous sodium sulfate, the solvent
was removed under reduced pressure, the solid residue was
recrystallized from boiling n-hexane (90 mL; crystallization at
-20 °C over a period of 24 h), and the precipitate was isolated by
filtration and washed with cold (0 °C) n-hexane (40 mL). This
purification step was repeated three times, followed by drying of
the product in vacuo (11 mbar, 20 °C, 2 h) to give 5a in 57% yield
(11.0 g, 30.8 mmol) as a colorless crystalline solid; mp 131-132
°C. 1H NMR (500.1 MHz, CDCl3): δ 0.56 (s, 6 H, SiCH3), 1.32 (s,
12 H, CCH3), 6.85-6.88 (m, 1 H, H-3, C5H3N), 7.48-7.50 (m, 2
H, H-3/H-5, C6H4), 7.77-7.81 (m, 3 H, H-2/H-6, C6H4, H-4,
C5H3N), 8.26-8.27 (m, 1 H, H-6, C5H3N). 13C NMR (125.8 MHz,
CDCl3): δ -2.6 (SiCH3), 24.8 (CCH3), 83.9 (CCH3), 109.2 (d, 2JCF
Preparation of (4-Bromophenyl)(2-fluoro-5-pyridyl)dimeth-
ylsilane (4a). A 2.5 M solution of n-butyllithium in hexanes (4.7
mL, 11.8 mmol of n-BuLi) was added dropwise at -70 °C within
20 min to a stirred solution of 1,4-dibromobenzene (2.77 g, 11.7
mmol) in diethyl ether (35 mL). After the addition was complete,
the mixture was stirred at -75 °C for 2 h. Subsequently, a solution
of 3a (2.19 g, 11.8 mmol) in diethyl ether (10 mL) was added
dropwise at -75 °C within 1 h, and the resulting mixture was stirred
at -75 °C for 30 min and then warmed to 20 °C within 18 h. Water
(45 mL) was added, the organic layer was separated, and the
aqueous phase was extracted with diethyl ether (3 × 40 mL). The
organic extracts were combined and dried over anhydrous sodium
sulfate, the solvent was removed under reduced pressure, and the
residue was purified by bulb-to-bulb distillation (150 °C/0.1 mbar)
to give 4a in 74% yield as a colorless liquid (2.71 g, 8.74 mmol).
1H NMR (500.1 MHz, CDCl3): δ 0.55 (s, 6 H, SiCH3), 6.86-6.90
(m, 1 H, H-3, C5H3N), 7.31-7.34 (m, 2 H, H-3/H-5, C6H4),
7.46-7.49 (m, 2 H, H-2/H-6, C6H4), 7.77-7.81 (m, 1 H, H-4,
C5H3N), 8.24-8.25 (m, 1 H, H-6, C5H3N). 13C NMR (75.5 MHz,
4
) 34.9 Hz, C-3, C5H3N), 130.5 (d, JCF ) 4.8 Hz, C-5, C5H3N),
133.3 (C-3/C-5, C6H4), 134.1 (C-2/C-6, C6H4), 140.0 (C-1, C6H4),
3
3
146.9 (d, JCF ) 7.3 Hz, C-4, C5H3N), 153.0 (d, JCF ) 13.4 Hz,
C-6, C5H3N), 164.6 (d, 1JCF ) 240.7, C-2, C5H3N), BC not detected.
11B NMR (160.5 MHz, CDCl3): δ 30.1. 19F NMR (376.5 MHz,
CDCl3): δ -67.0. 29Si NMR (99.4 MHz, CDCl3): δ -8.2 (d, JSiF
) 1.8 Hz). Anal. Calcd for C19H25BFNO2Si: C, 63.87; H, 7.05; N,
3.92. Found: C, 63.65; H, 7.01; N, 4.09.
5
2
CDCl3): δ -2.7 (SiCH3), 109.3 (d, JCF ) 34.9 Hz, C-3, C5H3N),
4
124.5 (C-1, C6H4), 130.0 (d, JCF ) 4.7 Hz, C-5, C5H3N), 131.2
(C-2/C-6, C6H4), 135.3 (C-4, C6H4), 135.5 (C-3/C-5, C6H4), 146.8
Preparation of (2-Chloro-5-pyridyl)dimethyl(4-(4,4,5,5-tet-
ramethyl-1,3,2-dioxaborolan-2-yl)phenyl)silane (5b). A 1.6 M
solution of tert-butyllithium in n-pentane (25 mL, 40.0 mmol of
t-BuLi) was added dropwise at -75 °C within 90 min to a stirred
solution of 4b (10.3 g, 31.5 mmol) in tetrahydrofuran (220 mL),
and the mixture was stirred at this temperature for 2 h. Subsequently,
4,4,5,5-tetramethyl-2-propyloxy-1,3,2-dioxaborolane11 (7.60 g, 40.8
mmol) was added dropwise at -75 °C within 30 min, and the
mixture was stirred at this temperature for 2 h and then warmed to
20 °C within 18 h. The solvent was removed under reduced
pressure, diethyl ether (240 mL) and water (240 mL) were added,
the organic layer was separated, and the aqueous phase was
extracted with diethyl ether (3 × 240 mL). The organic extracts
were combined and dried over anhydrous sodium sulfate, the solvent
was removed under reduced pressure, the solid residue was
recrystallized from boiling n-hexane (200 mL; crystallization at -20
°C over a period of 24 h), and the precipitate was isolated by
filtration and washed with cold (0 °C) n-hexane (30 mL). The
product was dried in vacuo (0.05 mbar, 20 °C, 4 h) to give 5b in
80% yield (9.38 g, 25.1 mmol) as a yellowish crystalline solid; mp
155-156 °C. 1H NMR (500.1 MHz, CDCl3): δ 0.56 (s, 6 H, SiCH3),
3
3
(d, JCF ) 7.3 Hz, C-4, C5H3N), 152.9 (d, JCF ) 13.4 Hz, C-6,
C5H3N), 164.6 (d, 1JCF ) 240.9 Hz, C-2, C5H3N). 19F NMR (376.5
MHz, CDCl3): δ -66.6. 29Si NMR (59.6 MHz, CDCl3): δ -7.5
5
(d, JSiF ) 1.8 Hz). Anal. Calcd for C13H13BrFNSi: C, 50.33; H,
4.22; N, 4.51. Found: C, 50.52; H, 4.49; N, 4.91.
Preparation of (4-Bromophenyl)(2-chloro-5-pyridyl)dimeth-
ylsilane (4b). A 2.5 M solution of n-butyllithium in hexanes (18
mL, 45.0 mmol of n-BuLi) was added dropwise at -70 °C within
45 min to a stirred solution of 1,4-dibromobenzene (10.5 g, 44.5
mmol) in diethyl ether (110 mL). After the addition was complete,
the mixture was stirred at -70 °C for 2 h. Subsequently, a solution
of 3b (9.00 g, 44.6 mmol) in diethyl ether (40 mL) was added
dropwise at -70 °C within 2 h, and the resulting mixture was stirred
at -70 °C for 30 min and then warmed to 20 °C within 19 h. Water
(160 mL) was added, the organic layer was separated, and the
aqueous phase was extracted with diethyl ether (3 × 120 mL). The
organic extracts were combined and dried over anhydrous sodium
sulfate, and the solvent was removed under reduced pressure. The
residue was purified by column chromatography on silica gel (silica
gel, 32-63 µm (ICN 02826); eluent, n-hexane/ethyl acetate (9:1
(v/v))) to afford 4b in 71% yield as a yellowish crystalline solid
(10.4 g, 31.8 mmol); mp 65-66 °C. 1H NMR (300.1 MHz, CDCl3):
δ 0.55 (s, 6 H, SiCH3), 7.27 (dd, 3JHH ) 7.9 Hz, 5JHH ) 0.9 Hz, 1
H, H-3, C5H3N), 7.30-7.34 (m, 2 H, H-3/H-5, C6H4), 7.47-7.51
(m, 2 H, H-2/H-6, C6H4), 7.64 (dd, 3JHH ) 7.9 Hz, 4JHH ) 2.1 Hz,
3
5
1.32 (s, 12 H, CCH3), 7.25 (dd, JHH ) 7.9 Hz, JHH ) 0.8 Hz, 1
H, H-3, C5H3N), 7.47-7.49 (m, 2 H, H-3/H-5, C6H4), 7.64 (dd,
4
3JHH ) 7.9 Hz, JHH ) 2.0 Hz, 1 H, H-4, C5H3N), 7.78-7.79 (m,
2 H, H-2/H-6, C6H4), 8.42 (dd, 4JHH ) 2.0 Hz, 5JHH ) 0.8 Hz, 1 H,
H-6, C5H3N). 13C NMR (125.8 MHz, CDCl3): δ -2.7 (SiCH3),
24.8 (CCH3), 83.9 (CCH3), 123.9 (C-3, C5H3N), 131.9 (C-5,
C5H3N), 133.3 (C-3/C-5, C6H4), 134.2 (C-2/C-6, C6H4), 139.7 (C-
1, C6H4), 144.4 (C-4, C5H3N), 152.7 (C-2, C5H3N), 154.7 (C-6,
C5H3N), BC not detected. 11B NMR (160.5 MHz, CDCl3): δ 30.1.
29Si NMR (99.4 MHz, CDCl3): δ -7.9. Anal. Calcd for
C19H25BClNO2Si: C, 61.06; H, 6.74; N, 3.75. Found: C, 61.33; H,
6.78; N, 3.78.
4
5
1 H, H-4, C5H3N), 8.40 (dd, JHH ) 2.1 Hz, JHH ) 0.9 Hz, 1 H,
H-6, C5H3N). 13C NMR (75.5 MHz, CDCl3): δ -2.7 (SiCH3), 124.0
(C-3, C5H3N), 124.7 (C-1, C6H4), 131.3 (C-2/C-6, C6H4), 131.4
(C-5, C5H3N), 135.0 (C-4, C6H4), 135.5 (C-3/C-5, C6H4), 144.3
(C-4, C5H3N), 152.9 (C-2, C5H3N), 154.5 (C-6, C5H3N). 29Si
NMR (59.6 MHz, CDCl3): δ -7.2. Anal. Calcd for C13H13BrClNSi:
C, 47.79; H, 4.01; N, 4.29. Found: C, 47.80; H, 3.93; N, 4.31.
Crystal Structure Analyses. Suitable single crystals of
1a · 0.5MeC(O)Me, 1b, 2, 4b, and 5a were obtained by crystal-
lization at 20 °C from n-hexane/acetone/water (30:10:1 (v/v/v) (1a);
700:300:1 (v/v/v) (1b)), at 20 °C from n-hexane/diethyl ether (1:2
(v/v) (2)), at 20 °C from n-hexane (4b), and at -20 °C from
n-hexane (5a), respectively. The crystals were mounted in inert oil
(perfluoropolyalkyl ether, ABCR) on a glass fiber and then
transferred to the cold nitrogen gas stream of the diffractometer
(1a · 0.5MeC(O)Me, 2, and 5a, Stoe IPDS, graphite-monochromated
Mo KR radiation (λ ) 0.710 73 Å); 1b and 4b, Bruker-Nonius
Kappa-APEX2 CCD system with Go¨bel mirror, Mo KR radiation
Preparation of (2-Fluoro-5-pyridyl)dimethyl(4-(4,4,5,5-tet-
ramethyl-1,3,2-dioxaborolan-2-yl)phenyl)silane (5a). A 1.6 M
solution of tert-butyllithium in n-pentane (43.5 mL, 69.6 mmol of
t-BuLi) was added dropwise at -75 °C within 90 min to a stirred
solution of 4a (16.7 g, 53.8 mmol) in tetrahydrofuran (310 mL),
and the mixture was stirred at this temperature for 2 h. Subsequently,
4,4,5,5-tetramethyl-2-propyloxy-1,3,2-dioxaborolane11 (12.9 g, 69.3
mmol) was added dropwise at -75 °C within 30 min, and the
mixture was stirred at this temperature for 2 h and then warmed to
20 °C within 18 h. The solvent was removed under reduced
pressure, diethyl ether (400 mL) and water (400 mL) were added,

3224 Organometallics, Vol. 28, No. 11, 2009
Troegel et al.
(λ ) 0.710 73 Å)). The structures were solved by direct methods.15
All non-hydrogen atoms were refined anisotropically.16 A riding
model was employed in the refinement of the hydrogen atoms.
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with The
Cambridge Crystallographic Data Centre as supplementary publica-
tion nos. CCDC-729170 (1a · 0.5MeC(O)Me), CCDC-729171 (1b),
CCDC-729172 (2), CCDC-729173 (4b), and CCDC-729174 (5a).
Copies of the data can be obtained free of charge on application to
the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax,
(+44)1223/336033; e-mail, deposit@ccdc.cam.ac.uk).
Acknowledgment. Financial support for this study from
AstraZeneca (Mo¨lndal, Sweden) is gratefully acknowledged.
Supporting Information Available: Figures, tables, and CIF
files, the latter giving atomic coordinates and equivalent isotropic
displacement parameters, anisotropic displacement parameters,
experimental details of the X-ray diffraction studies, and bond
lengths and angles of 1a · 0.5MeC(O)Me, 1b, 2, 4b, and 5a. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
(15) (a) Sheldrick, G. M. SHELXS-97; University of Go¨ttingen,
Go¨ttingen, Germany, 1997. (b) Sheldrick, G. M. Acta Crystallogr., Sect. A
1990, 46, 467–473.
(16) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
OM900175M