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RSC Advances
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M. Suzuki, H. Doi, K. Kato, M. Bjorkman, B. Långstrom,
pene in yields of 114 and 109% (based on methyl iodide
consumption), respectively, or yields of 3.6 and 3.3% (based
on boronic acid ester consumption), respectively (see the
Y. Watanabe and R. Noyori, Tetrahedron, 2000, 56,
8263–8273; (d) M. Bjorkman, H. Doi, B. Resul, M. Suzuki,
¨
¨
R. Noyori, Y. Watanabe and B. Långstrom, J. Labelled
details in ESI ). Such a mixture of methylated product and
3
Compd. Radiopharm., 2000, 43, 1327–1334; (e) M. Suzuki,
the alkene were difficult to separate the desired product,
causing the reduction of chemical purity.
¨
H. Doi, T. Hosoya, B. Långstrom and Y. Watanabe, TrAC,
Trends Anal. Chem., 2004, 23, 595–607. For the use of an
alkynyltributylstannane, see: (f) T. Hosoya, M. Wakao,
Y. Kondo, H. Doi and M. Suzuki, Org. Biomol. Chem., 2004,
2, 24–27. For the use of an alkenyltributylstannane, see: (g)
T. Hosoya, K. Sumi, H. Doi, M. Wakao and M. Suzuki, Org.
Biomol. Chem., 2006, 4, 410–415; (h) H. Doi, I. Ban,
A. Nonoyama, K. Sumi, C. Kuang, T. Hosoya, H. Tsukada
and M. Suzuki, Chem.–Eur. J., 2009, 15, 4165–4171. For the
use of a heteroarenyl-substituted tributylstannane, see: (i)
M. Suzuki, K. Sumi, H. Koyama, Siqin, T. Hosoya,
M. Takashima-Hirano and H. Doi, Chem.–Eur. J., 2009,
15, 12489–12495; (j) H. Koyama, Siqin, Z. Zhang, K. Sumi,
Y. Hatta, H. Nagata, H. Doi and M. Suzuki, Org. Biomol.
Chem., 2011, 9, 4287–4294; (k) M. Suzuki, M. Takashima-
Hirano, H. Koyama, T. Yamaoka, K. Sumi, H. Nagata,
H. Hidaka and H. Doi, Tetrahedron, 2012, 68, 2336–2341.
For the use of an arylboronic acid pinacol ester, see: (l)
M. Kanazawa, K. Furuta, H. Doi, T. Mori, T. Minami, S. Ito
and M. Suzuki, Bioorg. Med. Chem. Lett., 2011, 21,
2017–2020. For the C–[18F]fluoromethylation, see: (m)
H. Doi, M. Goto and M. Suzuki, Bull. Chem. Soc. Jpn.,
2012, 85, 1233–1238.
7 The previously reported reaction conditions of [Pd(OAc)2],
tricyclohexylphosphine (P(C6H11)3), and K3PO4?H2O in THF
at RT for 16 h for the sp3–sp3-type Suzuki–Miyaura
coupling of alkyl halides including methyl iodide with an
B-n-alkyl-9-borabicyclo[3.3.1]nonane (B-n-alkyl-9-BBN) were
attempted for our rapid methylation, but the reaction
hardly proceeded under the conditions CH3I/B-benzyl-9-
BBN/[Pd(OAc)2]/P(C6H11)3/K3PO4 (1 : 40 : 1 : 4 : 2 molar
ratio) in THF at reflux for 5 min (10%, see the details in
ESI ). Therefore, 9-BBN is not a suitable substrate for PET
3
probe synthesis. For alkyl–alkyl Suzuki cross coupling of
alkyl halides and tosylates with B-n-alkyl-9-BBN, see: (a)
T. Ishiyama, S. Abe, N. Miyaura and A. Suzuki, Chem. Lett.,
1992, 691–694; (b) M. R. Netherton, C. Dai, K. Neuschu¨tz
and G. C. Fu, J. Am. Chem. Soc., 2001, 123, 10099–10100; (c)
J. H. Kirchhoff, C. Dai and G. C. Fu, Angew. Chem., Int. Ed.,
2002, 41, 1945–1947; (d) M. R. Netherton and G. C. Fu,
Angew. Chem., Int. Ed., 2002, 41, 3910–3912; (e) G. Seidel
and A. Fu¨rstner, Chem. Commun., 2012, 48, 2055–2070.
8 (a) A. F. Littke and G. C. Fu, Angew. Chem., Int. Ed., 1998,
37, 3387–3388; (b) A. F. Littke, C. Dai and G. C. Fu, J. Am.
Chem. Soc., 2000, 122, 4020–4028; (c) A. F. Littke,
L. Schwarz and G. C. Fu, J. Am. Chem. Soc., 2002, 124,
6343–6348.
9 (a) S. W. Wright, D. L. Hageman and L. D. McClure, J. Org.
Chem., 1994, 59, 6095–6097; (b) L. Deloux and M. Srebnik, J.
Org. Chem., 1995, 60, 3276–3277. See also (c) L. Garnier,
B. Plunian, J. Mortier and M. Vaultier, Tetrahedron Lett.,
1996, 37, 6699–6700.
10 P. J. Riss, S. Lu, S. Telu, F. I. Aigbirhio and V. W. Pike,
Angew. Chem., Int. Ed., 2012, 51, 1–6.
11 E. D. Hostetler, G. E. Terry and H. D. Burns, J. Labelled
Compd. Radiopharm., 2005, 48, 629–634.
2 For the rapid C–[11C]methylation by sp3–sp3-type coupling
by the use of sodium enolates of the 2-arylacetic esters, see:
(a) M. Takashima-Hirano, M. Shukuri, T. Takashima,
M. Goto, Y. Wada, Y. Watanabe, H. Onoe, H. Doi and
M. Suzuki, Chem.–Eur. J., 2010, 16, 4250–4258.
3 M. E. Phelps, PET: Molecular Imaging and Its Biological
Applications, Springer, New York, Berlin, Heidelberg, 2004.
4 The n-pentane by-product was detected by GC {GL Science
TC-1701 column (60 m 6 0.25 mm i.d.), carrier gas: He,
flow rate: 0.70 mL min21, injector temperature: 280 uC,
detector temperature: 280 uC, column temperature: initial
30 uC, final 100 uC, temperature gradient: +10 uC min21
,
12 The reaction at 120 uC was conducted using an ampoule
sealed with a flame under Ar.
from 6 to 13 min, and 20 uC min21 from 23 to 28 min,
retention time, n-pentane: 23.5 min} without quantitative
analysis owing to the volatility (bp 35–36 uC).
13 The use of excess amounts of boronic acid ester substrate 1
and the Pd0–phosphine complex is important to efficiently
promote the reaction. Thus, the reaction of methyl iodide
with 1.5, 5, 10, and 20 equiv. of 1 using 40 mmol methyl
iodide under the conditions of CH3I/1/[Pd{P(tert-C4H9)3}2]/
CsF (1 : 1.5–20 : 1 : 10 molar ratio) in 90 : 10 DMF/H2O (v/
v, 4.0 mL) at 80 uC for 5 min afforded 2 in yields of 58, 63,
68, and 72%, respectively. Although the reaction was
monitored after 30 min and 1 h, the yields were not
improved. The reaction using twofold excess amounts of
[Pd{P(tert-C4H9)3}2] (2 equiv. for CH3I) and 10 equiv. of 1 at
80 uC for 5 min gave 2 in 91% high yield, while the reaction
using a lesser amount (0.1 equiv.) of [Pd{P(tert-C4H9)3}2]
and 1.5 equiv. of 1 under the same conditions gave 2 in
only 11% yield.
5 (a) A. C. Frisch and M. Beller, Angew. Chem., Int. Ed., 2005,
44, 674–688; (b) N. Kambe, J. Terao and T. Iwasaki, J. Synth.
Org. Chem. Jpn., 2011, 69, 1271–1281.
6 The reaction of alkylboronic acid ester, 3-phenylpropylboro-
nic acid pinacol ester, was conducted under the conditions
of CH3I/boronic acid ester/[Pd2(dba)3]/P(C6H11)3/K3PO4
(1 : 40 : 0.5 : 2 : 2 molar ratio) in 90 : 10 DMF/H2O (v/v) at
60 and 80 uC, 7b giving butylbenzene in 1 and 51% yields,
respectively, with the contaminant 3-phenyl-1-propene
produced by b-elimination in 3 and 24% yields (based on
methyl iodide consumption), respectively, or 0.1 and 0.6%
yields (based on boronic acid ester consumption), respec-
tively. Optimized conditions for the rapid C–methylation,
CH3I/boronic acid ester/[Pd2(dba)3]/P(o-CH3C6H4)3/K2CO3
(1 : 40 : 0.5 : 2 : 2 molar ratio) and CH3I/boronic acid
ester/[Pd{P(tert-C4H9)3}2]/CsF (1 : 40 : 1 : 10 molar ratio) in
90 : 10 DMF/H2O (v/v) at 80 uC were attempted for this
alkylboronic acid ester, giving undesired 3-phenyl-1-pro-
14 J. Uenishi, J.-M. Beau, R. W. Armstrong and Y. Kishi, J. Am.
Chem. Soc., 1987, 109, 4756–4758.
15 K. Menzel and G. C. Fu, J. Am. Chem. Soc., 2003, 125,
3718–3719.
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