Rapid catalyst-free carbon-carbon bonds coupling reaction under ambient conditions and ultrasonic irradiation

Article abstract of DOI:10.3184/030823407X256109

The catalyst-free coupling reaction of sodium tetraphenylborate with hypervalent iodine compounds was achieved under ultrasonic irradiation in water without a base, providing a convenient and rapid method for the formation of carbon-carbon bonds in good yield.

Full text of DOI:10.3184/030823407X256109

JOURNAL OF CHEMICAL RESEARCH 2007
NOꢀEMBER, 617–618
RESEARCH PAPER 617
Rapid catalyst-free carbon–carbon bonds coupling reaction under
ambient conditions and ultrasonic irradiation
Qinghong Shi*
College of Food Science and Biotechnology Engineering, Zhejiang Gongshang University, Hangzhou 310035, Zhejiang, P. R. China
The catalyst-free coupling reaction of sodium tetraphenylborate with hypervalent iodine compounds was achieved
under ultrasonic irradiation in water without a base, providing a convenient and rapid method for the formation of
carbon–carbon bonds in good yield.
Keywords: coupling reaction, sodium tetraphenylborate, hypervalent iodine compounds, ultrasound
The formation of carbon–carbon bonds is very important in
organic synthesis. The Suzuki reaction (palladium-catalysed
cross-coupling of aryl halides with boronic acids) is one of
the most versatile and utilised reactions for the selective
construction of carbon–carbon bonds, in particular for the
formation of biaryls.1 In order to improve and simplify
the Suzuki reaction, a wide range of metal complexes has
been used as catalyst in these coupling reactions, attention
particularly being focused on palladium. Since the use of metal
catalysts leads to the generation of waste which can have a
number of problems associated with it, the eradication of the
catalyst from the Suzuki reaction offers significant advantages.
Recently, Leadbeater and Marco first reported a catalyst-free
Suzuki coupling reaction: aryl halides reacted with arylboronic
investigated. They are shown in Scheme 1 and the results are
summarised in Table 1.
From Table 1, it is noteworthy that except for iodosylbenzene
2d (entry 4), all hypervalent iodine compounds reacted with
sodium tetraphenylborate smoothly under ultrasonic irradiation
and reaction completed in 5 min, giving products in good
yields (Entries 1 to 5). Iodanes 2a and 2c in the reaction needed
shorter time and gave higher yields of product compared with
2b and 2e, which meant that iodanes with strongly acidic
anions were more effective in the reaction (Entries 1 and 3).
The hypervalent iodonium salts 2f–2h also reacted with sodium
tetraphenylborate easily and 2h gave a stereoselective product
3d, which showed that ultrasound enhanced the reaction rates
greatly compared with the result reported by Yan (that the
6
acids under microwave irradiation without catalyst in water at
reaction did not occur in a normal manner).
2
1
50°C and afforded biaryls in good yields. However, due to
In summary, a rapid and efficient method for formation
of carbon–carbon bonds is afforded by the catalyst-free
coupling reaction under ultrasonic irradiation in a water
the development of pressure using water as solvent and the
need for specialised sealed vessels, this method is not suitable
for organic reactions carried out at atmospheric pressure.
In order to find an alternative to halides, Yan et al. focused
their attention on hypervalent iodine compounds due to their
high reactivity and excellent yields in Suzuki reactions under
X
ultrasound
Ph BNa
+
Ar
I
Ar Ph
4
H O
2
Y
1
2
3
3
mild conditions, their readily availability and their nontoxic
properties. They found that when iodanes were mixed with
sodium tetraphenylborate, they reacted smoothly in water
Scheme 1
Table 1 The results of the coupling reactions of sodium
tetraphenylborate with hypervalent iodine compounds under
ultrasonic irradiation.
at room temperature and provided good yields of coupling
products.4 They also investigated the coupling reaction
under microwave irradiation, and found that the microwave
5
irradiation could shorten the reaction times greatly. Because
Entry
Hypervalent
iodine compounds
Product
Time/ Yield/
a
min
%
temperature control is some difficult in microwave irradiation
reactions at atmospheric pressure and in order to develop a
fast and efficient catalyst-free coupling reaction at ambient
temperature, I have investigated the reaction of hypervalent
iodine compounds with sodium tetraphenylborate under
ultrasonic irradiation. Here, I report for the first time a fast
catalyst-free coupling reaction at ambient temperature in
water under ultrasonic irradiation, which can extend the scope
of catalyst-free Suzuki coupling reactions.
OH
1
Ph
I
OTs
Ph–Ph
3
85
2a
3a
2
3
4
PhI(OAc)2
2b
3a
3a
3a
Ph
5
3
72
82
50
PhI(OCOCF3)2
2
c
PhI
O
The sonochemical reaction was carried out in a thermostatted
2d
10
OH
(25°C) ultrasonic cleaning bath of frequency 50 kHz in air.
Initially molar equivalents of sodium tetraphenylborate and
I
5
hydroxy(tosyloxy)iodobenzene were mixed. It was found that
after only 3 min an 85% yield of biphenyl was obtained under
ultrasonic irradiation. Then, reaction with different molar
equivalents of sodium tetraphenylborate to hydroxy(tosyloxy)
iodobenzene were carried out, and it was found that all these
reactions occurred easily and gave good yields of the same
product. Equal equivalents of sodium tetraphenylborate and
hypervalent iodine compound was chosen as the most suitable
ratio. Under the optimal reaction conditions, the reactions
of sodium tetraphenylborate (1) with a series of hypervalent
iodine compounds (2) to produce coupling products (3) were
O
OH
C
O
C
O
2e
2
3b
5
5
3
70
72
75
+
-
6
7
Ph I Cl
2f
3a
3c
+
-
Ph
I PhBF Ph
4
Ph
2
2
g
Ph
Ph
8
+
-
I PhBF
Ph
4
h
3d
5
70
aIsolated yield.
*
Correspondent. E-mail: QinghongShi@hotmail.com
PAPER: 07/4817

6
18 JOURNAL OF CHEMICAL RESEARCH 2007
medium. This method has advantages over other procedures
in that it is simple, mild, high-yielding, and occurs at ambient
temperature. Furthermore, the utility of hypervalent iodine
compounds in organic syntheses was extended.
Received 28 August 2007; accepted 29 October 2007
Paper 07/4817
doi: 10.3184/030823407X256109
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[
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1
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2
minutes (shown in Table 1) in an ultrasonic cleaning bath (50 kHz).
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4
5
6
7
4
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1
569, 1481, 730 cm ; MS (70eꢀ, EI) m/z (%): 154 (M , 100).
2
3
4, 6853.
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1
0
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1
H NMR (CDCl ): d = 7.30–7.39 (m, 7H), 7.53 (m, 1H), 7.93 (m,
3
1
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11
-1
+
1
296 cm ; MS (70eꢀ, EI) m/z (%): 198 (M , 100).
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(
CDCl ): d = 7.22–7.41 (m, 6H), 7.51 (m, 4H); IR (KBr) n = 3064,
3
-
1
3
032, 1600,1500, 1262, 757, 691 cm ; MS (75eꢀ, EI) m/z (%): 178
+
(M , 100).
E-1, 2-diphenylethylene (3d): M.p. 120–121°C (Lit.3d 122–124°C).
1
H NMR (CDCl ): d = 7.15 (s, 2H), 7.21 (m, 2H), 7.34 (m, 4H),
3
7
6
.48 (m, 4H); IR (KBr) n = 3079, 3034, 1698, 1496, 1073, 966, 767,
-1
+
93 cm ; MS (75eꢀ, EI) m/z (%): 180 (M , 100).
PAPER: 07/4817