Suzuki reaction of bromoallenes with arylboronic acids using an air-stable palladium complex Pd(Ph2PCH2CO2)2 as a precatalyst

Article abstract of DOI:10.1016/j.cclet.2010.01.042

Suzuki reaction of bromoallenes with arylboronic acids was successfully performed by using an air-stable hemilabile P-O coordinated cyclopalladated complex Pd(Ph₂PCH₂CO₂)₂ as a precatalyst, and the corresponding

Full text of DOI:10.1016/j.cclet.2010.01.042

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Chinese Chemical Letters 21 (2010) 641–645
www.elsevier.com/locate/cclet
Suzuki reaction of bromoallenes with arylboronic acids using an
air-stable palladium complex Pd(Ph2PCH2CO2)2 as a precatalyst
*
Xin Du, Xiu Juan Feng , Ying Liu, Ren He, Ming Bao
*
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
Received 13 November 2009
Abstract
Suzuki reaction of bromoallenes with arylboronic acids was successfully performed by using an air-stable hemilabile P–O
coordinated cyclopalladated complex Pd(Ph2PCH2CO2)2 as a precatalyst, and the corresponding coupling products were obtained
in satisfactory to excellent yields. All products are unknown compounds which were characterized by 1H NMR, 13C NMR, IR, and
HRMS.
# 2010 Xiu Juan Feng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Suzuki reaction; Bromoallene; Palladium complex
The Suzuki reaction of organoboron reagents with organic halides represents one of the most versatile and
straightforward methods for construction of new carbon–carbon bond in the synthesis of fine chemicals,
agrochemicals, and active pharmaceutical intermediates as well as functional materials [1]. Aryl halides [1,2], alkyl
halides [1,3], allyl halides [1,4], vinyl halides [1,5], alkynyl halides [1,6] were frequently utilized as coupling partners
in the palladium-catalyzed coupling reaction over the past years. However, only three examples of Suzuki reaction
between bromoallenes and arylboronic acids using an air-sensitive palladium complex Pd(PPh3)4 as a catalyst were
reported in the past years [7]. During our continuous research on Suzuki coupling reaction [8], we found that the air-
stable hemilabile P–O coordinated cyclopalladated complex Pd(Ph2PCH2CO2)2 could be used as a precatalyst in the
Suzuki reaction of aryl bromides with arylboronic acids to obtain fluorinated biaryls in satisfactory to excellent yields
(Scheme 1). These observations encouraged us to expand the use of the palladium complex Pd(Ph2PCH2CO2)2 into
Suzuki reaction of bromoallenes [9]. Fortunately, the reaction of bromoallenes with arylboronic acids proceeded
smoothly in the presence of catalytic amount of Pd(Ph2PCH2CO2)2 to offer diaryl substituted allenes in also
satisfactory to excellent yields. Here we wish to report our preliminary results.
1. Experimental
1H and 13C NMR spectra were recorded in CDCl3 solution on a Varian Inova-400 spectrometer (400 MHz for 1H,
100 MHz for 13C). The chemical shifts are reported in ppm downfield (d) from TMS. IR spectra were recorded on a
* Corresponding authors.
E-mail addresses: xiujuan.feng@163.com (X.J. Feng), mingbao@dlut.edu.cn (M. Bao).
1001-8417/$ – see front matter # 2010 Xiu Juan Feng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.01.042

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X. Du et al. / Chinese Chemical Letters 21 (2010) 641–645
Scheme 1. Coupling reaction of aryl bromides with arylboronic acids catalyzed using Pd(Ph2PCH2CO2) as a precatalyst.
2
NEXUS FT-IR spectrometer. High-resolution mass spectra were recorded on a Q-TOF mass spectrometry
(Micromass, England) equipped with Z-spray ionization source. TLC was carried out on SiO2 (silica gel 60 F254
Merck). Flash chromatography was carried out on SiO2 (silica gel 60, 200–300 mesh).
,
1.1. General procedure for Suzuki reaction
A mixture of bromoallene (1.0 mmol), arylboronic acid (1.5 mmol), K3PO4Á3H2O (798.9 mg, 3.0 mmol) and
Pd(Ph2PCH2CO2)2 (17.8 mg, 3 mol%) in 3 mL of THF/H2O (v/v = 1:1) was stirred at room temperature under
nitrogen atmosphere for 6 h. The product was extracted with diethyl ether (5 mL Â 3), and the combined organic layer
was dried over magnesium sulfate. Then the solvent was removed under reduced pressure, and the crude product was
purified by silica gel column chromatography (eluent: hexane) to afford desired pure product (Table 1).
1
1-Chloro-2-(3-phenylhepta-1,2-dienyl)benzene 3a: Colorless oil; H NMR (400 MHz, CDCl3): d 7.44–7.46 (m,
3H), 7.31–7.37 (m, 3H), 7.10–7.23 (m, 3H), 6.97 (t, 1H, J = 2.8 Hz), 2.54–2.60 (m, 2H), 1.56–1.62 (m, 2H), 1.43–1.46
(m, 2H), 0.92 (t, 3H, J = 7.6 Hz); 13C NMR (100 MHz, CDCl3): d 207.5, 135.8, 132.3, 132.1, 129.8, 128.5, 128.5,
128.1, 127.9, 127.1, 126.8, 126.1, 126.1, 110.2, 94.2, 30.1, 29.8, 22.6, 13.9; IR (neat) n: 2956, 2928, 2859, 1933, 1493,
1476, 1442, 1049, 1032, 750, 692 cmÀ1; HRMS (EI) calcd. for C19H19Cl: 282.1175 [M]+; found: 282.1185.
1-Chloro-2-(3-(4-methylphenyl)hepta-1,2-dienyl)benzene 3b: Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.43–
7.46 (m, 1H), 7.32–7.36 (m, 3H), 7.08–7.17 (m, 4H), 6.95 (t, 1H, J = 2.8 Hz), 2.52–2.57 (m, 2H), 2.33 (s, 3H), 1.52–
1.62 (m, 2H), 1.39–1.47 (m, 2H), 0.91 (t, 3H, J = 7.6 Hz); 13C NMR (100 MHz, CDCl3): d 207.4, 137.0, 132.8, 132.6,
132.2, 129.9, 129.3, 129.3, 128.1, 127.9, 126.8, 126.1, 126.1, 110.2, 94.1, 30.1, 29.9, 22.7, 21.1, 14.0; IR (neat) n:
2957, 2927, 2859, 1931, 1510, 1476, 1443, 1049, 1032, 826, 751 cmÀ1; HRMS (EI) calcd. for C20H21Cl: 296.1332
[M]+; found: 296.1321.
1-Chloro-2-(3-(4-methoxyphenyl)hepta-1,2-dienyl)benzene 3c: Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.44
(dd, 1H, J = 2.0, 8.0 Hz), 7.33–7.38 (m, 3H), 7.07–7.17 (m, 2H), 6.93–6.96 (m, 1H), 6.86 (dd, 2H, J = 2.0, 6.8 Hz),
3.78 (s, 3H), 2.51–2.56 (m, 2H), 1.53–1.60 (m, 2H),1.39–1.45 (m, 2H), 0.91 (t, 3H, J = 7.6 Hz); 13C NMR (100 MHz,
CDCl3): d 207.2, 158.9, 132.6, 132.1, 129.9, 128.1, 127.9, 127.8, 127.3, 127.3, 126.8, 114.0, 114.0, 109.7, 94.1, 55.3,
30.1, 30.0, 22.7, 14.0; IR (neat) n: 2956, 2930, 1931, 1607, 1510, 1248, 1178, 1037, 834, 752 cmÀ1; HRMS (EI) calcd.
for C20H21OCl: 312.1281 [M]+; found: 312.1290.
1
1-Chloro-4-(3-phenylhepta-1,2-dienyl)benzene 3d: Colorless oil; H NMR (400 MHz, CDCl3): d 7.43 (d, 2H,
J = 7.6 Hz), 7.33 (d, 2H, J = 7.2 Hz), 7.21–7.30 (m, 5H), 6.48 (t, 1H, J = 3.2 Hz), 2.54–2.58 (m, 2H), 1.53–1.58 (m,
2H), 1.40–1.45 (m, 2H), 0.91 (t, 3H, J = 7.6 Hz); 13C NMR (100 MHz, CDCl3): d 206.6, 135.9, 133.2, 132.5, 128.8,
128.8, 128.5, 128.5, 127.9, 127.9, 127.2, 126.1, 126.1, 110.4, 96.9, 30.1, 29.8, 22.6, 13.9; IR (neat) n: 2956, 2928,
2859, 1933, 1489, 1090, 1012, 845, 692 cmÀ1; HRMS (EI) calcd. for C19H19Cl: 282.1175 [M]+; found: 282.1177.
1
1-Chloro-2-(3-phenylnona-1,2-dienyl)benzene 3e: Colorless oil; H NMR (400 MHz, CDCl3): d 7.43–7.46 (m,
3H), 7.30–7.37 (m, 3H), 7.10–7.24 (m, 3H), 6.97 (t, 1H, J = 2.8 Hz), 2.54–2.59 (m, 2H), 1.54–1.65 (m, 2H), 1.23–1.42
(m, 6H), 0.87 (t, 3H, J = 7.6 Hz); 13C NMR (100 MHz, CDCl3): d 207.7, 136.0, 132.5, 132.3, 130.0, 128.7, 128.7,
128.3, 128.1, 127.3, 127.0, 126.3, 126.3, 110.4, 94.4, 31.9, 30.3, 29.4, 28.1, 22.8, 14.2; IR (neat) n: 2954, 2927, 2856,
1934, 1494, 1475, 1442, 1050, 1033, 751, 694 cmÀ1; HRMS (EI) calcd. for C21H23Cl: 310.1488 [M]+; found:
310.1494.
1-Chloro-2-(3-(4-methylphenyl)nona-1,2-dienyl)benzene 3f: Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.43–
7.46 (m, 1H), 7.32–7.36 (m, 3H), 7.09–7.17 (m, 4H), 6.95 (t, 1H, J = 2.4 Hz), 2.52–2.57 (m, 2H), 2.33 (s, 3H), 1.54–
1.63 (m, 2H), 1.26–1.43 (m, 6H), 0.85 (t, 3H, J = 7.2 Hz); 13C NMR (100 MHz, CDCl3): d 207.6, 137.1, 132.9, 132.7,
132.3, 130.0, 129.4, 129.4, 128.3, 128.0, 127.0, 126.2, 126.2, 110.2, 94.2, 31.9, 30.3, 29.4, 28.1, 22.8, 21.3, 14.2; IR

X. Du et al. / Chinese Chemical Letters 21 (2010) 641–645
643
Table 1
Suzuki reaction of bromoallenes with arylboronic acids using Pd(Ph2PCH2CO2)2 as a precatalysta
.
Entry
Bromoallene 1
Arylboronic acid 2
Product 3
Yield (%)b
1
83
2
3
4
83
93
87
5
6
86
84
7
91
a
All products are unknown compounds, and were characterized by IR, 1H and 13C NMR, and HRMS.
Isolated yields.
b

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X. Du et al. / Chinese Chemical Letters 21 (2010) 641–645
(neat) n: 2955, 2926, 2856, 1932, 1511, 1467, 1443, 1050, 825, 752 cmÀ1; HRMS (EI) calcd. for C22H25Cl: 324.1645
[M]+; found: 324.1650.
1-Chloro-2-(3-(4-methoxyphenyl)nona-1,2-dienyl)benzene 3g: Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.43–
7.48 (m, 2H), 7.34–7.37 (m, 2H), 7.09–7.17 (m, 2H), 6.95 (d, 1H, J = 8.4 Hz), 6.94 (s, 1H), 6.87 (d, 1H, J = 8.8 Hz),
3.80 (s, 3H), 2.50–2.56 (m, 2H), 1.54–1.63 (m, 2H), 1.27–1.39 (m, 6H), 0.85 (t, 3H, J = 7.2 Hz); 13C NMR (100 MHz,
CDCl3): d 207.3, 158.9, 133.7, 132.8, 132.3, 130.0, 128.3, 127.9, 127.4, 127.4, 127.0, 114.3, 114.2, 109.9, 94.3, 55.5,
31.9, 30.4, 29.4, 28.1, 22.8, 14.2; IR (neat) n: 2956, 2928, 2856, 1931, 1607, 1510, 1251, 1041, 824, 771 cmÀ1; HRMS
(EI) calcd. for C22H25OCl: 340.1594 [M]+; found: 340.1602.
2. Results and discussion
Suzuki reactions of bromoallenes 1 with arylboronic acids 2 were performed under optimized conditions, the
catalysis results of which are summarized in Table 1. Reactions of 1a with 2a, 2b, and 2c gave the corresponding
coupling products, 3a, 3b, and 3c, in satisfactory to excellent yields (83%, 83%, and 93%, respectively, entries 1–3).
When 1b and 1c were treated with 2a, respectively, the corresponding coupling products, 3d and 3e, were obtained in
also high yields (87% and 86%, respectively, entries 4 and 5). Finally, we examined the reactions of 1c with 2b and 2c,
and found these reactions proceeded also smoothly to provide coupling products, 3f and 3g, in 84% and 91% yields,
respectively (entries 6 and 7). Interestingly, the chlorine atom on the substrates 1 did not changed during the Suzuki
reactions, and which could make the products 3a–g more useful in further organic transformation. The chlorine atom
linked at the para or ortho position of aromatic ring, did not influenced on the coupling reaction yields. Even the R2 on
1 was changed from n-butyl group to n-hexyl group, which has longer chain than the n-butyl group, the desired
coupling products were also obtained in high yields. In the above mentioned Suzuki coupling reactions, the palladium
complex Pd(Ph2PCH2CO2)2 exhibited high catalytic activity in the absence of other phosphine ligand. It further
indicated that the Ph2PCH2CO2 is an excellent bidentate ligand for the palladium-catalyzed Suzuki coupling reaction.
In conclusion, we have successfully expanded the use of the palladium complex Pd(Ph2PCH2CO2)2 into Suzuki
reaction of bromoallenes as a precatalyst, and obtained diaryl substituted allenes in satisfactory to excellent yields. It
was considered that the palladium (II) complex Pd(Ph2PCH2CO2)2 was reduced to palladium (0) complex in situ by
arylboronic acid at first, and then the palladium (0) complex generated catalyzed the coupling reactions of
bromoallenes with arylboronic acids.
Acknowledgments
We are grateful to the National Natural Science Foundation of China (No. 20603005) for financial support. This
work was partly supported by the program for Changjiang Scholars and Innovative Research Teams in Universities
(No. IRT0711).
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