Methanol-promoted borylation of arylamines: A simple and green synthetic method to arylboronic acids and arylboronates

Article abstract of DOI:10.1055/s-0033-1339118

A Sandmeyer borylation of arylamines via a SN₂Ar pathway promoted by methanol with sodium nitrite and hydrochloric acid as diazotization agent has been developed, which provide a simple and green synthetic method to arylboronic acids and arylboronates. Georg Thieme Verlag Stuttgart New York.

Full text of DOI:10.1055/s-0033-1339118

LETTER
▌1577
lMetteer thanol-Promoted Borylation of Arylamines: A Simple and Green Synthetic
Method to Arylboronic Acids and Arylboronates
Methanol-Promoted Borylation of Aryla
a
mines
a
a
a
a,b
Cong-Jun Zhao, Dong Xue,* Zhi-Hui Jia, Chao Wang, Jianliang Xiao
a
Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education and School of Chemistry and
Chemical Engineering, Shaanxi Normal University, Xi’an 710062, P. R. of China
Fax +86(29)81530727; E-mail: xuedong_welcome@snnu.edu.cn
b
Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK
Received: 28.02.2014; Accepted after revision: 18.04.2014
cat. [Pd]
cat. [Cu]
Abstract: A Sandmeyer borylation of arylamines via a SN Ar path-
2
ArN X
+
+
B pin
ArBpin
ArBpin
(
(
(
a)
b)
2
2
2
way promoted by methanol with sodium nitrite and hydrochloric
acid as diazotization agent has been developed, which provide a
simple and green synthetic method to arylboronic acids and arylbo-
ronates.
ArN X
2
2
B pin
2
Key words: methanol, borylation, arylamines, arylboronic acids,
arylboronates, diazotization
eosin Y
c) ArN2X
d) ArNH2
+
B2pin2
ArBpin
ArBpin
visible light
1
2
) t-BuONO
) B2pin2, BPO or 80 °C
(
Arylboronic acids and boronates are useful building
blocks in transition-metal-catalyzed cross-coupling reac-
1,2
This work:
ArNH2
tions due to their low toxicity and high stability. Gener-
ally, the reaction of Grignard or lithium reagents with
B2pin2, r.t.
ArBpin
3
trialkyl borates are the general synthetic routes. Unfortu-
45–97%
2
4 examples
NaNO2, HCl, H2O
MeOH
nately, these methods have low functional-group compat-
ibility because of the strong nucleophilicity of the
B2(OH)4, r.t.
55–90%
4
reagents. The borylation of aryl halides and arenes via C–
ArB(OH)2
H activation5 catalyzed by transition metals have been
developed as complementary synthetic methods, which
show high functional-group tolerance. In addition, Lewis
acid catalyzed electrophilic borylation of electron-rich
,6
1
1 examples
Scheme 1 The borylation of arene diazonium salts or arylamines
7
arenes and an alkoxy base promoted nucleophilic boryla-
8
tinuing our recent work in aryldiazonium salts
chemistry, we would like to report a methanol-promoted
Sandmeyer borylation of arylamines via a SN Ar pathway
at room temperature with sodium nitrite and hydrochloric
acid as diazotization agent, affording arylboronic acids
and esters with high yields.
tion of organic halides provide useful transition-metal-
15
free methods for the preparation of arylboronic acids and
boronates, which avoid the high process cost and heavy-
metal impurities in the final products.
2
Aryldiazonium salts are as commonly used as surrogates
of aryl halides due to their rich reactivity and diverse
transformations.9
salts catalyzed by transition metals or by eosin Y under
visible light promoted photoredox catalysis provide an
useful approach toward arylboronic ester synthesis
,10
The most common method for the preparation of diazoni-
um salts is the treatment of aromatic amines with nitrous
acid. Usually, the nitrous acid is generated in situ from so-
The borylation of arene diazonium
1
1
1
2
16
dium nitrite and mineral acid. Following this standard
method, in our initial investigations, we focused on the di-
rect borylation of 4-toluidine (1a) with sodium nitrite and
hydrochloric acid as diazotization agent in the first step,
and bis(pinacolato)diboron was utilized as boron source
in the second step. The results shown in Table 1 reveal
that solvent is vital to this transformation. For nonprotonic
solvents, except for ethyl acetate, all gave no reaction
within one hour at room temperature (Table 1, entries 1–
(
Scheme 1). Very recently, Wang reported a Sandmeyer-
type borylation of arylamines by direct conversion of the
amino group of aniline derivatives into the boronate
group, which provide an entirely different approach to-
ward arylboronate synthesis.13 However, it is worth not-
ing that arylboronic acids could not be synthesized with
1
4
this method, and radical initiators, high temperature, or
diazotization agent tert-butyl nitrite (t-BuONO) are nec-
essary for the synthesis of pinacol arylboronates. In con-
9
). To our delight, when protic solvents such as AcOH and
MeOH were used, the yields increased to 50% and 74%
under identical conditions, respectively (Table 1, entry
1
0). Other alcohols except for ethylene glycol and glycer-
SYNLETT 2014, 25, 1577–1584
Advanced online publication: 28.05.2014
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
in, ethanol, tert-butanol, 2-methoxyethanol, trifluoretha-
DOI: 10.1055/s-0033-1339118; Art ID: st-2014-w0180-l
Georg Thieme Verlag Stuttgart · New York
nol, and 2-PrOH, all afforded the borylation products,
©

1578
C.-J. Zhao et al.
LETTER
albeit with low yields (Table 1, entries 13–17). Further Table 1 Optimization of the Cross-Coupling of Amine with Bis-
optimization was seen by changing the amount of B pin . (pinacolato)diborona
2
2
The use of one and two equivalents of B pin resulted in
2
2
NH2
Bpin
1) MeOH, NaNO , HCl
H2O, 0–5 °C, 30 min
2
the borylation product 2a with 38% and 60% yield at
room temperature (Table 1, entry 18). However, the addi-
tion of four equivalents of B pin to the reaction did not
2
) B2pin2, solvent, r.t.,1 h
1
a
2a
2
2
improve the isolated yield (Table 1, entry 20).
Entry
Solvent
Yield (%)b
With the optimal conditions in hand, the substrate scope
was subsequently investigated.17 First, a wide range of
aryl amines 1 with substitutes, such as alkyl, OMe, NO2,
COOEt, Br, CN, Cl, F, I, CN, NH , OCF , and OH in the
1
2
3
4
5
6
7
8
9
CH
Cl
trace
22
2
2
EtOAC
MeCN
acetone
THF
2
3
phenyl, underwent coupling with B pin (2) at ambient
trace
trace
trace
trace
trace
trace
50
2
2
temperature, and the desired products were isolated in
good yields. The results shown in Table 2 indicate that
aryl amines with electron-withdrawing or electron-donat-
ing substituents all could give the desired products with
good yields. The borylation showed good tolerance to var-
ious functional groups on the aryl amines such as OH,
toulene
DMF
CO Et, CN, CX (X = F, Cl, Br, and I) under the reaction
2
DMSO
AcOH
conditions, and excellent yields were achieved for the re-
actions (2d–m). Notably, the amine group could be trans-
formed to the boronate group selectively simply by
controlling the amount of hydrochloric acid and sodium
nitrite. For the substrate p-phenylenediamine, the desired 11
monoamine and monoproduct 2l could be obtained with
1
0
MeOH
ethylene glycol
glycerin
EtOH
74
trace
trace
51
1
2
53% yield without protection of the amino group. At the
same time, for the substrate 4,4′-diaminobiphenyl, the de- 13
sired diboronate product 2x is obtained with 75% yield by
1
4
Me COH
47
3
doubling the amount of hydrochloric acid and sodium ni-
trite. Disubstituted aromatic amines were also tested, giv- 15
ing good yields (Table 2, 2u,v). The substrate scope could
also be extended to amines with a naphthyl ring or biphe-
nyl (Table 2, 2w–x). All these arylboronates have found 17
2-methoxyethanol
25
1
6
Me CHOH
61
2
trifluorethanol
MeOH
63
widespread applications in organic synthesis, as repre-
sented by the Suzuki–Miyaura cross-coupling reaction. In
1
8c
38
addition, bis(neopentyl glycolato)diboron can play the 19d
MeOH
60
same role that react with arylamine at the same reaction
conditions. As shown in Scheme 2, the desired borylated
product 4a could be obtained with 65% isolated yield
2
0e
MeOH
73
a
Reaction conditions: in the first step: amine (0.5 mmol), MeOH (1.0
mL), HCl (3 M, 0.5 mL), H O (0.5 mL), NaNO (0.035 g), 0–5 °C, 30
(Scheme 2), which suggested its potential application for
2
2
min; in the second step: B pin (1.5 mmol), solvent (1.0 mL), r.t., 1 h.
2
2
the preparation of arylboronates.
b
c
d
e
Isolated yield;
In the next step, we apply our process toward the synthesis
of arylboronic acids with tetrahydroxydiboron [B (OH) ]
Conditions: 1 equiv bis(pinacolato)diboron was used.
Conditions: 2 equiv bis(pinacolato)diboron were used.
Conditions: 4 equiv bis(pinacolato)diboron were used.
2
4
1
4
as boron source. A wide range of aryl amines 1 with sub-
stitutes, such as alkyl, OMe, F, Cl, Br, NO , and COOEt
2
in the phenyl, underwent coupling with B (OH) at ambi- ing substituents all could give the desired products with
2
4
ent temperature, and the desired products were isolated in good yields. Likewise, this borylation showed good toler-
1
9
good yields. The results shown in Table 3 indicate that ance to various functional groups on the aryl amines such
aryl amines with electron-withdrawing or electron-donat- as CO
Et, NO , CX (X = F, Cl, Br) under the reaction con-
2
2
O
O
1
) HCl, H2O, MeOH
NaNO2, 30 min
H2N
B
O
B
+
B
O
O
2
) MeOH, 1 h, r.t.
O
OMe
MeO
4
a, 65%
Scheme 2 The coupling of p-anisidine with bis(neopentyl glycolato)diboron
Synlett 2014, 25, 1577–1584
© Georg Thieme Verlag Stuttgart · New York

LETTER
Methanol-Promoted Borylation of Arylamines
1579
ditions, and excellent yields were achieved for the reac- heterocyclic boronate 2z, which is usually not easy to syn-
tions (3d–f,h,i), which are available for further thesize and use as the key intermediate for the synthesis of
18
functionalization.
3z, a potent inhibitor for the treatment of osteoporosis
Scheme 3).
(
To test the viability of the method with more complex
substrates, we applied the borylation to the preparation of
Table 2 The Synthesis of Arylboronates from Arylamines with Bis(pinacolato)borane as Boron Source
NH2
1) MeOH, NaNO2
HCl, H2O, 0–5 °C
Bpin
R
R
2) B2pin2, r.t.
1
2
Entry
1
Substrate
Product
Yield (%)b
74
NH2
Bpin
1
a
2a
2b
NH2
Bpin
2
3
57
86
1b
NH2
Bpin
MeO
MeO
1c
2c
NH2
Bpin
4
5
6
7
8
54
62
73
77
55
F
F
1
d
e
2d
NH2
Bpin
Cl
Cl
1
2e
NH2
Bpin
Br
Br
1f
2f
NH2
Bpin
I
I
1g
2g
NH2
Bpin
F3CO
F3CO
1h
2h
NH2
Bpin
9
75
57
EtO2C
EtO C
2
1i
2i
NH2
Bpin
1
0
NC
NC
1j
2j
©
Georg Thieme Verlag Stuttgart · New York
Synlett 2014, 25, 1577–1584

1580
C.-J. Zhao et al.
LETTER
Table 2 The Synthesis of Arylboronates from Arylamines with Bis(pinacolato)borane as Boron Source (continued)
NH2
1) MeOH, NaNO2
HCl, H2O, 0–5 °C
Bpin
R
R
2) B2pin2, r.t.
1
2
Entry
Substrate
Product
Yield (%)b
NH2
Bpin
Bpin
Bpin
1
1
97
O2N
O2N
1k
2k
NH2
1
2
3
53
93
H2N
H2N
1l
2l
NH2
1
HO
HO
1m
2m
NH2
NH2
Bpin
Bpin
1
4
5
45
48
1
1
1
1
n
2n
Cl
Cl
1
o
p
q
2o
OH
OH
NH2
NH2
Bpin
Bpin
1
6
7
60
62
2p
2q
1
NH2
NH2
NH2
Bpin
Bpin
Bpin
18
19
20
52
55
96
OMe
OMe
1
r
s
2r
Cl
Cl
1
2s
NO2
NO2
1t
2t
Synlett 2014, 25, 1577–1584
© Georg Thieme Verlag Stuttgart · New York

LETTER
Methanol-Promoted Borylation of Arylamines
1581
Table 2 The Synthesis of Arylboronates from Arylamines with Bis(pinacolato)borane as Boron Source (continued)
NH2
1) MeOH, NaNO2
HCl, H2O, 0–5 °C
Bpin
R
R
2) B2pin2, r.t.
1
2
Entry
Substrate
Product
Yield (%)b
NH2
Bpin
21
72
1u
2u
NH2
Bpin
MeO
MeO
2
2
3
96
85
OMe
OMe
1v
v
NH2
Bpin
2
1w
2w
NH2
Bpin
24
75
H2N
pinB
1x
2x
a
Reaction conditions: in the first step: amine (0.5 mmol), MeOH (1.0 mL), HCl (3 M, 0.5 mL), H O (0.5 mL), NaNO (0.035 g), 0–5 °C, 30
2
2
min; in the second step: B pin (1.5 mmol), MeOH (1.0 mL), r.t., 1 h.
2
2
b
c
Isolated yield.
Conditions: HCl (1.0 mL), H O (1.0 mL).
2
In addition, the borylation of p-anisidine at a 2 g scale was To gain understanding of the reaction mechanism, the fol-
carried out under the conditions of Scheme 4, giving the lowing borylation reaction of 4-toluidine with bis(pinaco-
desired 4-methoxyphenylboronic ester in 83% isolated lato)diboron as boron source in methanol was carried out.
yield, which demonstrate the practical applicability of the In the presence of radical trap, 2,2,6,6-tetramethylpiperid-
method (Scheme 4).
inoxyl (TEMPO), the desired compound was obtained
NH2
+
O
O
1
) HCl, H2O, MeOH
NaNO2, 30 min
B
O
O
B
B
N
O
O
2) MeOH, 1 h, r.t.
N
HN
1z (1.0 equiv)
HN
(
3.0 equiv)
2
z, 68%
O
N
CN
H
two steps
N
NH
3
z
Scheme 3 The coupling of 1-(4-aminophenyl)piperazine with bis(pinacolato)diboron
©
Georg Thieme Verlag Stuttgart · New York
Synlett 2014, 25, 1577–1584

1582
C.-J. Zhao et al.
LETTER
with 74% isolated yield (Scheme 5, eq. 1). However, un- Table 3 The Synthesis of Arylboronic Acids from Arylamines with
a
1
3
Tetrahydroxydiboron B (OH) as Boron Source (continued)
2 4
like the results reported by Wang, the addition of
TEMPO to the borylation reaction of 4-toluidine with
bis(pinacolato)diboron did not suppressed the borylation
process significantly, the same borylated product was iso-
lated with 68% yield (Scheme 5, eq. 2), which lends sup-
port that the radical species were not involved in our
borylation reaction and a direct nucleophilic borylation
OH
B
1
) MeOH, NaNO2
HCl, H2O, 0–5 °C
NH2
OH
R
R
2
) B2(OH)4, MeOH, r.t
1
3
Yield (%)b
Entry Substrate
Product
via a SN Ar pathway maybe preferred.
2
OH
B
NH2
Table 3 The Synthesis of Arylboronic Acids from Arylamines with
a
Tetrahydroxydiboron B (OH) as Boron Source
OH
2
4
8
55
O2N
OH
B
O2N
3h
1) MeOH, NaNO2
HCl, H2O, 0–5 °C
NH2
1
k
OH
R
R
2) B2(OH)4, MeOH, r.t
OH
NH2
1
3
B
OH
9
65
73
Entry Substrate
Product
Yield (%)b
2
EtO C
EtO2C
1
i
OH
B
3
i
NH2
OH
B
OH
NH2
1
72
OH
1
1
b
a
10
3
3
b
a
OH
B
NH2
1u
3j
OH
2
3
4
90
86
67
OH
B
NH2
OH
MeO
1
1
65
MeO
OH
B
OMe
NH2
OMe
OH
1
v
3k
MeO
MeO
a
Reaction conditions: in the first step: amine (0.5 mmol), MeOH (1.0
O (0.5 mL), NaNO (0.035 g), 0–5 °C, 30
min; in the second step: B (OH) (1.5 mmol), MeOH (1.0 mL), r.t., 1
1
c
3
c
mL), HCl (3 M, 0.5 mL), H
2
2
OH
B
2
4
NH2
NH2
NH2
h.
b
OH
Isolated yield.
F
F
1
d
3
d
O
B
OH
NH2 1) MeOH, HCl, NaNO , H O
2
2
O
B
OH
2
) MeOH, B2pin2, r.t.
5
73
Cl
MeO
MeO
.95g, 83%
Cl
1
1
e
3
e
Scheme 4 A large-scale coupling of p-anisidine with bis(pinacolato)-
diboron
OH
B
OH
6
7
74
62
Br
A plausible mechanism is shown in Scheme 6 on the basis
of the above experiments. First, a nucleophilic boryl moi-
ety was formed by activation of the diboron reagent under
the effect of methanol, this preactivation increases the re-
activity of the diboron compounds. The aryldiazonium
cation generated from aryl amine is the electrophile
(Scheme 5, eq. 3) and the activated diboron reagent is a
nucleophile. Then, the activated boron intermediate A at-
tacks the aryl diazonium salt to form transient intermedi-
Br
1
f
3
f
OH
NH2
B
OH
F3C
F3C
1
y
3
g
ate B via a SN Ar pathway, which is subsequently
2
Synlett 2014, 25, 1577–1584
© Georg Thieme Verlag Stuttgart · New York

LETTER
Methanol-Promoted Borylation of Arylamines
1583
NH2
1
) HCl, H2O, MeOH
NaNO2, 30 min
O
O
O
O
O
O
(
(
1)
2)
B
+
B
B
2) MeOH, 1 h, r.t.
7
4%
(
1.0 equiv)
NH2
(3.0 equiv)
1
) HCl, H2O, MeOH
O
O
O
O
O
NaNO , 30 min
2
+
B
B
+ TEMPO
B
O
2) MeOH, 1 h, r.t.
6
8%
(
1.0 equiv)
N2BF4
(3.0 equiv)
(2.0 equiv)
O
O
O
B
O
O
O
MeOH, 2 h, r.t.
B
(
3)
B
+
7
1%
(
1.0 equiv)
(3.0 equiv)
Scheme 5 Mechanistic investigations
O
O
Ar
B
R
R
N2
NaNO2 + HCl
+
NH2
N N
R
+
N
N
O
O
+
MeO
B
– H+
+
MeOH
B
O
O
O
O
O
O
–
O
MeOH
B
B
C
O
B
B
O
O
B
A
polarized B–B bond
Scheme 6 Possible reaction pathway
transformed into the borylation product through N elimi- Acknowledgment
2
nation and 2-methoxy-4,4,5,5-tetramethyl-1,3,2-dioxa-
We are grateful for the financial support of the National Natural Sci-
ence Foundation of China (21372148) and by the 111 Project, Pro-
gram for Chang Jiang Scholars and Innovative Research Team in
University (IRT 1070), and Shaanxi Innovative Team of Key Sci-
ence and Technology (2013KCT-17).
borolane C formation. The latter compound is confirmed
1
1
by B NMR spectroscopic study.
In conclusion, an effective methanol-promoted coupling
of arylamine with diboron compounds at room tempera-
ture has been developed under metal-free conditions. This
protocol could be applied to the synthesis of arylboronic Supporting Information for this article is available online
acids utilizing arylamine and tetrahydroxydiboron at
http://www.thieme-connect.com/products/ejournals/journal/
1
0.1055/s-00000083. SunogIpimirf antoSuIpg
n
ori
m
B (OH) , bis(pinacolato)diboron and bis(neopentyl gly-
2
4
colato)diboron as boron source. This borylation process
has the following features: (1) arylamines are inexpensive
and easily available starting materials; (2) the borylation
showed good tolerance to various functional groups on the
aryl amines; (3) sodium nitrite is used as diazotization
agent; (4) the reaction is carried out at room temperature
without the use of catalyst, which provide a simple and
green synthetic method to arylboronic acids and arylboro-
nates.
References and Notes
(
1) For reviews of applications of arylboronates and arylboronic
acid derivatives, see: (a) Miyaura, N. In Metal-Catalyzed
Cross-Coupling Reactions; Meijere, A. D., Ed.; Wiley-
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Boronic Acids: Preparation and Applications in Organic
Synthesis and Medicine; Hall, D. G., Ed.; Wiley-VCH:
Weinheim, 2005, 123. (c) Suzuki, A. In Metal-Catalyzed
©
Georg Thieme Verlag Stuttgart · New York
Synlett 2014, 25, 1577–1584

1584
C.-J. Zhao et al.
LETTER
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(
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G. A.; Trice, S. L. J. S.; Kennedy, M.; Dreher, S. D.; Tudge,
M. T. J. Am. Chem. Soc. 2012, 134, 11667. (b) Molander, G.
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Masuda, Y. Synlett 2006, 1867.
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5) For reviews, see: (a) Ishiyama, T.; Miyaura, N.
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2
011, 40, 1992.
(
6) For recent examples of transition-metal-catalyzed boryl
substitution of haloarenes and arene C–H borylation, see:
(16) Hoffman, R. V. Org. Synth. 1981, 60, 121.
(17) General Procedure for the Synthesis of Aryboronate
Esters
(a) Dai, H.-X.; Yu, J.-Q. J. Am. Chem. Soc. 2012, 134, 134.
(
b) Sogabe, Y.; Namikoshi, T.; Watanabe, S.; Murata, M.
To a solution of arylamine (0.5 mmol, 1.0 equiv) in MeOH
(1.0 mL) was added HCl (0.5 mL, 1.5 mmol, 3.0 equiv)
Synthesis 2012, 44, 1233. (c) Kawamorita, S.; Ohmiya, H.;
Iwai, T.; Sawamura, M. Angew. Chem. Int. Ed. 2011, 50,
followed by H O (0.5 ml). This mixture was stirred 2 min,
2
8
363. (d) Kawamorita, S.; Miyazaki, T.; Ohmiya, H.; Iwai,
T.; Sawamura, M. J. Am. Chem. Soc. 2011, 133, 19310.
e) Yamamoto, T.; Morita, T.; Takagi, J.; Yamakawa, T.
and the NaNO solution (0.25 mL) was then added. The
2
NaNO solution was prepared by dissolving 35 mg of
2
(
NaNO in H O (0.25 mL). This mixture was stirred 30 min
2
2
Org. Lett. 2011, 13, 5766. (f) Tang, W.; Keshipeddy, S.;
Zhang, Y.; Wei, X.; Savoie, J.; Patel, N. D.; Yee, N. K.;
Senanayake, C. H. Org. Lett. 2011, 13, 1366. (g) Ros, A.;
Estepa, B.; López-Rodríguez, R.; Álvarez, E.; Fernández,
R.; Lassaletta, J. M. Angew. Chem. Int. Ed. 2011, 50, 11724.
at 0–5 °C followed by B pin (2, 381 mg, 1.5 mmol, 3.0
equiv) in MeOH (1.0 mL). This mixture was stirred 60 min.
2 2
H O (10 mL) was added to the reaction mixture, then
2
extracted with CH Cl (50 mL, 3×). The combined organic
2
2
layers were washed with sat. NaHCO , dried over Na SO ,
3
2
4
(
h) Nguyen, D. H.; Pérez-Torrente, J. J.; Lomba, L.; Victoria
Jiménez, M.; Lahoz, F. J.; Oro, L. A. Dalton Trans. 2011,
0, 8429. (i) Kleeberg, C.; Dang, L.; Lin, Z. Y.; Marder, T.
followed by evaporation, and the crude residue was purified
by flash chromatography.
(18) Chen, C.-Y.; Dagneau, P.; Grabowski, E. J. J.; Oballa, R.;
O’Shea, P.; Prasit, P.; Robichaud, J.; Tillyer, R.; Wang, X.
J. Org. Chem. 2003, 68, 2633.
4
B. Angew. Chem. Int. Ed. 2009, 48, 5350.
(
7) For reviews, see: (a) Ingleson, M. J. Synlett 2012, 23, 1411.
(
2
b) De Vries, T. S.; Prokofjevs, A.; Vedejs, E. Chem. Rev.
012, 112, 4246. For recent examples, see: (c) Ishida, N.;
Moriya, T.; Goya, T.; Murakami, M. J. Org. Chem. 2010, 75,
709. (d) Del Grosso, A.; Muryn, C. A.; Pritchard, R. G.;
(19) General Procedure for the Synthesis of Arylboronic
Acids
To a solution of arylamine (0.5 mmol, 1.0 equiv) in MeOH
(1.0 mL) was added HCl (0.5 mL, 1.5 mmol, 3.0 equiv),
8
Ingleson, M. J. Organometallics 2010, 29, 241. (e) Del
Grosso, A.; Singleton, P. J.; Muryn, C. A.; Ingleson, M. J.
Angew. Chem. Int. Ed. 2011, 50, 2102. (f) Hatakeyama, T.;
Hashimoto, S.; Seki, S.; Nakamura, M. J. Am. Chem. Soc.
followed by H O (0.5 ml). This mixture was stirred 2 min,
2
and the NaNO solution (0.25 mL) was then added. The
2
NaNO solution was prepared by dissolving 35 mg of
2
NaNO in H O (0.25 mL). This mixture was stirred 30 min
2
2
2
011, 133, 18614. (g) Prokofjevs, A.; Kampf, J. W.; Vedejs,
at 0–5 °C, followed by HCl (135 mg, 1.5 mmol, 3.0
E. Angew. Chem. Int. Ed. 2011, 50, 2098. (h) Del, Grosso.
A.; Helm, M. D.; Solomon, S. A.; Caras-Quintero, D.;
Ingleson, M. J. Chem. Commun. 2011, 47, 12459.
equivalents) in MeOH (1.0 mL). This mixture was stirred 60
min. H O (10 mL) was added to reaction mixture, then
2
extracted with CH Cl (50 mL, 3×). The combined organic
2
2
(
i) Solomon, S. A.; Del Grosso, A.; Clark, E. R.; Bagutski,
V.; McDouall, J. J. W.; Ingleson, M. J. Organometallics
012, 31, 1908. (j) Niu, L.; Yang, H.; Yang, D.; Fua, H. Adv.
layer was dried over Na SO , followed by evaporation to
give the products.
2 4
2
Synlett 2014, 25, 1577–1584
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