Microwave promoted palladium-catalyzed phenylation of aroyl chlorides and sodium tetraphenylborate

Article abstract of DOI:10.1081/SCC-100108241

A rapid and efficient method for synthesis of unsymmetrical ketones involves reaction of sodium tetraphenylborate with aroyl chlorides in the presence of catalytic amount Pd(PPh₃)₂Cl₂ under microwave irradiation to give the corresponding phenyl ketones 3a-j in 87-98% yield.

Full text of DOI:10.1081/SCC-100108241

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MICROWAVE PROMOTED PALLADIUM-CATALYZED
PHENYLATION OF AROYL CHLORIDES AND SODIUM
TETRAPHENYLBORATE
Jin-Xian Wang a , Bangguo Wei a , Yulai Hu a , Zhanxiang Liu a & Yihua Yang a
a Department of Chemistry , Institute of Chemistry , Northwest Normal University, 805
An Ning Road (E.), Lanzhou, 730 070, P. R. China
Published online: 09 Nov 2006.
To cite this article: Jin-Xian Wang , Bangguo Wei , Yulai Hu , Zhanxiang Liu & Yihua Yang (2001) MICROWAVE
PROMOTED PALLADIUM-CATALYZED PHENYLATION OF AROYL CHLORIDES AND SODIUM TETRAPHENYLBORATE, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 31:24, 3885-3890,
DOI: 10.1081/SCC-100108241
To link to this article: http://dx.doi.org/10.1081/SCC-100108241
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SYNTHETIC COMMUNICATIONS, 31(24), 3885–3890 (2001)
MICROWAVE PROMOTED PALLADIUM-
CATALYZED PHENYLATION OF
AROYL CHLORIDES AND SODIUM
TETRAPHENYLBORATE
Jin-Xian Wang,* Bangguo Wei, Yulai Hu,
Zhanxiang Liu, and Yihua Yang
Institute of Chemistry, Department of Chemistry,
Northwest Normal University, 805 An Ning
Road (E.) Lanzhou, 730 070, P. R. China
ABSTRACT
A rapid and efficient method for synthesis of unsymmetri-
cal ketones involves reaction of sodium tetraphenylborate
with aroyl chlorides in the presence of catalytic amount
Pd(PPh3)2Cl2 under microwave irradiation to give the corres-
ponding phenyl ketones 3a–j in 87–98% yield.
The palladium-catalyzed cross-coupling reaction of organoborate
compounds with organic electrophiles is very attractive method for new
carbon–carbon bond formation in organic synthesis.1 These coupling reac-
tions can tolerate many functional groups and utilized extensively in the
organic synthesis of natural products. From the viewpoint of organic syn-
thesis, a number of recent reports on using sodium tetraphenylborate with
*Corresponding author.
3885
Copyright & 2001 by Marcel Dekker, Inc.
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WANG ET AL.
acid chloride or alkyl iodides catalyzed by palladium(II) or (0) complex are
very interesting.2 There was also reported the reaction of Pd(OAc)2-cata-
lyzed phenylation of alkenes and sodium tetraphenylborate in the presence
of a suitable re-oxidant.2c
Microwave are known to accelerate many organic reactions in polar
solvents or in the absence of solvent and some important reviews have been
published.3 Recently, we have reported the synthesis of conjugated acetyl-
enic ketones catalyzed by copper(I) salts4 and chiral glycerol selenide ethers5
under microwave irradiation conditions. Several microwave assisted palla-
dium-catalyzed reactions have been reported recently.6
We now wish to report the synthesis of unsymmetrical ketones from
sodium tetraphenylborate and aroyl chlorides using Pd(PPh3)2Cl2 as cata-
lyzed under microwave irradiation. This method is simple, fast and affords
good yield. The reactions are show in the scheme and results are summa-
rized in Table 1.
Scheme.
Using the reaction of sodium tetraphenylborate with p-bromobenzoyl
chloride as an example, we investigated the effects of the power and time of
microwave irradiation for the formation of 3a. The results are summarized
in Table 2 and Table 3. It was found the high yield unsymmetric ketones can
be obtained at 525 W for 9 min under microwave irradiation conditions.
We also studied the effect of various solvents on the formation of 3a, it
was found that acetone or THF was the best solvent for the formation of 3a.
Bumagin2b et al. have reported the best solvent was acetone–water
(v/v ¼ 5 mL : 5 mL) catalyzed by Pd(OAc)2 for the formation of phenyl
ketone under conventional conditions, but when we use acetone–water
(v/v ¼ 9 mL : 1 mL or 5 mL : 5 mL) as solvent catalyzed by Pd(PPh3)2Cl2
under microwave irradiation condition, we only obtained substituted ben-
zoic acid. This is because aroyl chlorides was easily hydrolyzed under micro-
wave irradiation condition. The results are summarized in Table 4.

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AROYL CHLORIDES AND SODIUM TETRAPHENYLBORATE
3887
Table 1. Preparation of Unsymmetric Ketones 3a–j
Entrya
Productb
M.P. (Lit) (ꢀC)
Yieldc (%)
3a
3b
3c
3d
3e
3f
4-Br-C6H4COC6H5
2-Cl-C6H4COC6H5
4-Cl-C6H4COC6H5
C6H5COC6H5
3-Br-C6H4COC6H5
4-NO2-C6H4COC6H5
3-NO2-C6H4COC6H5
4-CH3-C6H4COC6H5
C6H5CH ¼ CHCOC6H5
4-CH3O-C6H4COC6H5
79–80/79–807
43–44/458
98
94
98
96
93
91
87
93
88
94
75–76/75–769
47–48/4710
68–69/7511
134–135/135–13612
96–97/95–95.513
56–57/579
3g
3h
3i
52–53/53–5414
58–59/599
3j
b
aMole ratio: NaBPh4: aroyl chloride: Pd(PPh3)2Cl2: KF ¼ 1:4.2:0.05:1.5. All prod-
ucts were determined by IR, 1H NMR and MS, and comparison with authentic
c
samples. Isolated yield.
Table 2. Effect of the Power of Microwave Irradiation on the Formation of 3a
Power (W)
Yield (%)
300
68
375
79
450
87
525
98
600
97
675
94
750
92
Table 3. Effect of the Time of Microwave Irradiation on the Formation of 3a
Time (min)
Yield (%)
4
6
7
8
9
10
97
12
98
45
69
86
91
98
Table 4. Effect of the Solvent on the Formation of 3a
(CH3)2CO/H2O (mL : mL)
9 : 1 5 : 5
Solvent
C6H6 CH2Cl2 THF (CH3)2CO CH3CN
28 96 98 81
Yield (%) 16
Trace 0
The effect of various bases used in the formation of 3a was studied and
KF was found to be the best base for the reaction. When KF was used as
base, the yield of 3a is very high (98%), whereas the yield is only 58 and 43%
respective when reaction use K2CO3 or Et3N as base. Other bases were

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WANG ET AL.
Table 5. Impact of Reaction Condition on the Formation of Compounds 3a–j
Conventional Heating
Microwave Heating
Entry
tc (min)
Yield (%)
Power (W) tmw (min) Yield (%) tc/tmw
3a
3b
3c
3d
3e
3f
3g
3h
3i
1200
1200
1200
1200
1200
1200
1200
1200
1200
1200
90
82
89
87
84
80
76
85
68
77
525
525
525
525
525
525
525
525
525
525
9
9
9
9
9
9
9
9
9
9
98
94
98
96
93
91
87
93
88
94
133
133
133
133
133
133
133
133
133
133
3j
studied for the reaction and their suitability is in the following order
KF > NaOH > K2CO3 > Et3N. When the reaction was carried out in the
absence of base, the yield of 3a was very poor.
Microwave irradiation and conventional heating for the synthesis of
compounds 3a–j has been compared and result are summarized in Table 5.
The results show that the synthesis of compounds 3a–j under microwave
irradiation were 133 times faster than under conventional heating. The ratio
between the reaction time using conventional reflux and microwave irradia-
tion (tc/tmw) under the same conditions, quantifies the microwave heating
effect.
EXPERIMENTAL
Microwave irradiation was carried out with a commercial microwave
1
oven GlanzWP 750B at 2450 Hz. H NMR spectra were recorded in CDCl3
on a BRUKER PT 200 A. Spectrometer using tetramethylsilane as internal
standard. Chemical shifts were reported as d in ppm. IR spectra were mea-
sured with an Alpha centauri FI-IR spectrometer as KBr dics. Mass spectra
were recorded on a QP-1000A GC-MS using the impact mode (70 eV).
Melting points were determined with an electrothermal micromelting
point apparatus and are uncorrected. All solvents were used without further
purification. Dichlorobis(triphenylphosphine)palladium(II) was prepared
according to Ref.15
General Procedure for the Preparation of compounds 3a–j: A mixture
of sodium tetraphenylborate (1 mmol), aroyl chloride (4.2 mmol),

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3889
Pd(PPh3)2Cl2 (0.05 mmol), KF (1.5 mmol) and acetone 10 mL was irradiated
at 525 W for 9 min by microwaves under argon atmosphere. The precipitate
was filtrated and the filtrate was poured into a saturated aqueous sodium
chloride solution 50 mL and extracted with diethyl ether (20 mL ꢁ 3). The
extracts were washed with water (20 mL ꢁ 3) and then dried over with mag-
nesium sulfate. The dried diethyl ether solution was concentrated to yield
crude product which was purified by column chromatography on silica gel
(200–300 mesh) using petroleum/ethyl acetate (v/v ¼ 15 mL : 1 mL) as eluent
or recrystallized 3a–j in 87–98% yield.
ACKNOWLEDGMENTS
We thank the National Natural Science Foundation of China and the
Northwest Normal University Science and Technology Development
Foundation of China for financial support.
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Received in the Netherlands February 12, 2001

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