Pinacol coupling of aromatic aldehydes and ketones using magnesium in aqueous ammonium chloride under ultrasound

Article abstract of DOI:10.1081/SCC-120002400

The pinacol coupling reaction of aromatic aldehydes and ketones was performed in 8-95% yield with magnesium in 0.1 M aqueous NH₄C1 under ultrasound irradiation at r.t. for 3 h.

Full text of DOI:10.1081/SCC-120002400

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PINACOL COUPLING OF AROMATIC ALDEHYDES AND
KETONES USING MAGNESIUM IN AQUEOUS AMMONIUM
CHLORIDE UNDER ULTRASOUND
a
a
a
Ji-Tai Li , Yan-Jiang Bian , Hong-Jun Zang & Tong-shuang Li
a
Department of Chemistry , Hebei University , Baoding, 071002, P. R. China
Published online: 16 Aug 2006.
To cite this article: Ji-Tai Li , Yan-Jiang Bian , Hong-Jun Zang & Tong-shuang Li (2002) PINACOL COUPLING OF AROMATIC
ALDEHYDES AND KETONES USING MAGNESIUM IN AQUEOUS AMMONIUM CHLORIDE UNDER ULTRASOUND, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:4, 547-551, DOI:
10.1081/SCC-120002400
To link to this article: http://dx.doi.org/10.1081/SCC-120002400
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SYNTHETIC COMMUNICATIONS, 32(4), 547–551 (2002)
PINACOL COUPLING OF
AROMATIC ALDEHYDES AND
KETONES USING MAGNESIUM IN
AQUEOUS AMMONIUM CHLORIDE
UNDER ULTRASOUND
Ji-Tai Li,* Yan-Jiang Bian, Hong-Jun Zang,
andTong-shuang Li
Department of Chemistry, Hebei University,
Baoding 071002, P. R. China
ABSTRACT
The pinacol coupling reaction of aromatic aldehydes and
ketones was performed in 8–95% yield with magnesium
in 0.1 M aqueous NH Cl under ultrasound irradiation at r.t.
4
for 3 h.
The reductive coupling of carbonyl compounds is an important
method for the formation of 1,2-diols. A number of types of metal reagents,
1
2
3
4
5
6
7
such as Zn, Al(Hg), Ln, Mn, Sm, Te, Al, and Mg have been used to
8
9
carry out the pinacol coupling. Recently, Zn-Cu or In has also been found
to promote the pinacol-coupling under ultrasound irradiation. Herein, we
report the studies of using Mg for pinacol coupling of aromatic aldehydes
and ketones in aqueous media under ultrasound.
*
Corresponding author. E-mail: orgsyn@mail.hbu.edu.cn
47
5
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

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5
48
LI ET AL.
As shown in table and scheme, p-methoxy benzaldehyde and p-methyl
benzaldehyde were reacted with magnesium in 0.1 M ammonium chloride
aqueous solution, the corresponding pinacol-coupling products were
obtained in high yield (2f, 2h) under ultrasound. In the absence of ultra-
7
sound, a suspension of benzaldehyde and magnesium turning in aqueous
0.1 M NH Cl were stirred vigorously at room temperature overnight to
4
furnish 1,2-bis(4-methoxyphenyl)-1,2-diol (2f ) and 1,2-bis(4-methylphe-
nyl)-1,2-diol (2h) in 89 and 65% yield respectively. Our procedure both
results in 95% yield within 3 h. The yield of pinacol-coupling product
from some carbonyl compounds (2c, 2g, 2m, and 2n) was lower than
reported in above literature. According postulated mechanism for
magnesium-mediated pinacol coupling and reduction of carbonyl com-
7
pounds, ultrasonication was favorable for single electron transfer reaction
of the aldehydes, resulting in diols. At the same condition, ultrasonication
was favorable for reduction of ketones, resulting in reduction product.
In conclusion, we found magnesium to be effective for mediating
pinacol-coupling reactions in aqueous NH Cl under ultrasound.
4
EXPERIMENTAL
Liquid substrates were purified by distillation prior to use. IR spectra
1
were recorded on a Bio-Rad FTS-40 spectrometer (KBr). H NMR spectra
were measured on VXR-300S spectrometer (300 or 200 MHz) by using
CDCl as solvent and TMS as internal standard. Mass spectra were deter-
3
mined on an AEI MS-50 SD90 spectrometer (EI, 70 eV). Sonication was
performed in a Shanghai Branson-CQX ultrasonic cleaner with a frequency
of 25 kHz and a nominal power 500 W. The reaction flask was located at the
maximum energy area in the cleaner and the temperature of water bath was
controlled by addition or removal of water.
General Procedure
A 100 mL Pyrex flask was charged with the desired aldehyde or ketone
1, 1 mmol) Mg powder (0.55 g, 22 mmol), and 0.1 M aqueous NH Cl
(
4
(6 mL). The mixture was irradiated in the water bath of an ultrasonic cleaner
at room temperature for 3 h. The reaction was quenched with 3 M aqueous
HCl and extracted with ethyl acetate (3 ꢀ 15 ml). The combined organic
layers were washed with saturated aqueous NaHCO solution and brine,
3
dried over magnesium sulfate and filtered. The filtrate was concentrated
in vacuum to give a crude material, which was separated by column

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PINACOL COUPLING OF ALDEHYDES AND KETONES
549
Scheme.
chromatography on silica (200–300 mesh), eluted with petroleum ether
ꢁ
(
b.p. 60–90 C) or a mixture of petroleum ether and diethyl ether. The
authenticity of the product was established by their spectra.
a: dH 2.26 (s, 2H, OH), 4.70 (s, dl) and 4.83 (s, meso) (2H, phCH-),
2
.10–7.32 (m, 10H, Ar); m/z (%): 214 (1), 180 (7.6), 167 (12.5), 149 (6.0), 107
7
(
ꢂ1
93.8), 79 (100), 77 (73.8); nmax (KBr): 3400–3800 cm
.
2
b: d 2.98 (s, 2H, OH), 5.49 (s, meso) (2H, phCH-), 7.00–7.26 (m, 6H,
H
Ar); m/z (%): 352 (1), 305 (1.4), 233 (10), 175 (100), 145 (10), 111 (25), 77
ꢂ1
(
15); nmax (KBr): 3320–3400 cm
.
2c: dH 2.98 (s, 2H, OH), 5.19 (s, dl) and 5.49 (s, meso) (2H, phCH-),
7
.10–7.26 (m, 8H, Ar); m/z (%): 282 (10), 235 (12), 165 (5.5), 141 (100), 107
ꢂ1
(
19), 77 (10); nmax (KBr): 3380–3420 cm
.
2d: dH 2.89 (s, 2H, OH), 4.62 (s, dl) and 4.79 (s, meso) (2H, phCH-),
7
.12–7.20 (m, 8H, Ar); m/z (%): 263 (1.2), 251 (1.6), 178 (4.6), 165 (4.6), 141
ꢂ1
(
100), 113 (23.8), 77 (71.0); nmax (KBr): 3260–3318 cm
.
2e: dH 1.79 (s, 2H, OH), 4.44 (8, dl) (2H, -CH-OH), 6.29 (t, 2H,
-
2
1
CH¼CH-), 6.71 (d, 2H, -CH¼CH-), 7.24–7.41 (m, 10H, Ar); m/z (%):
64 (1.0), 248 (6.2), 232 (3.6), 219 (3.0), 157 (6.7), 134 (21.4), 133 (100),
15 (24.7), 91 (27.8), 77 (19.9), 55 (37.0); nmax (KBr): 3300–3380 cm
ꢂ1
.
2
f: d 2.90 (s, 2H, OH), 3.77 (s, dl) and 3.81 (s, meso) (s, 6H, OCH ),
H
3
4.64 (s, dl) and 4.75 (s, meso) (2H, phCH-), 6.73–7.21 (m, 8H, Ar); m/z
(
3
%): 274 (1), 256 (2), 227 (30), 137 (100), 109 (9), 77 (8); nmax (KBr):
ꢂ1
300–3380 cm
.
2
g: d 2.04 (s, 2H, -OH), 5.00 (s, dl) and 5.02 (s, meso) (2H, fur-CH-),
H
6.27 (m, 2H, 3,4-fur-H), 7.26 (m, 1H, 5-fur-H); m/z (%): 196 (10), 178
(
3
25), 152 (73), 137 (33), 98 (100), 84 (22), 49 (30); n
240–3300 cm
(KBr):
max
ꢂ1
.
2
h: dH 2.29 (s, 6H, CH ), 2.58 (s, 2H, OH), 4.65 (s, dl) and 4.72 (s,
3
meso) (2H, -CH-OH), 7.02–7.20 (m, 8H, Ar); m/z (%): 242 (1), 195 (6), 121
ꢂ1
(
100), 107 (12), 93 (19), 77 (13); nmax (KBr) 3280–3450 cm
.
2i: dH 2.20 (s, 2H, OH), 4.57 (s, 2H, phCH-), 5.92 (s, 4H, CH2),
6
1
.64–6.71 (m, 6H, Ar); m/z (%): 302 (1), 284 (2.5), 268 (5.0), 255 (11.8),
ꢂ1
51 (100), 123 (32), 93 (77.1), 65 (39.0); nmax (KBr): 3450–3490 cm
.

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5
50
LI ET AL.
Table. Pinacol-Coupling Mediated by Mg in 0.1 M Aqueous NH Cl Under
4
Ultrasound*

ORDER
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PINACOL COUPLING OF ALDEHYDES AND KETONES
551
2
j: d 2.52 (s, 6H, CH ), 6.11 (s, 2H, OH), 6.82–6.85 and 7.85–7.89 (m,
H
3
8
H, Ar); m/z (%): 282 (1), 266 (15), 221 (12), 177 (24), 162 (26), 151 (30), 135
ꢂ1
(
23), 120 (70), 85 (38), 77 (17), 57 (90); nmax (KBr): 3360–3450 cm
.
2
n: d 1.47 (s, dl) and 1.56 (s, meso) (6H, -CCH ), 2.2 (s, 2H, OH), 3.8
H
3
(
(
s, 6H, OCH ), 6.7–7.3 (m, 8H, Ar), m/z (%): 302 (1), 151 (100), 135 (5), 109
ꢂ1
3
4), 77 (3), 43 (60); nmax (KBr): 3200–3600 cm
.
ACKNOWLEDGMENTS
The project was supported by National Natural Science Foundation
of China (29872011), Educational Ministry of China and Educational
Department of Hebei Province (99014). The project was supported by
Natural Science Foundation of Hebei Province (299080).
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Received in the Netherlands March 19, 2001

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