2
J. Gao et al. / Journal of Organometallic Chemistry xxx (2015) 1e5
phase transfer groups [17] in aqueous/organic biphasic systems. We
once prepared a mononuclear copper(II) complex [Cu(II)L(H O)]I
1) (Scheme 1), which showed excellent catalytic activity towards
7.50 (t, J ¼ 7.6 Hz, 2H); 13C NMR (100 MHz, CDCl
3
, ppm): d 192.18,
2
2
136.23, 134.28, 129.52, 128.83.
(
the oxidative polymerization of 2,6-dimethylphenol [18]. Could
complex 1 work as a catalyst to initiate the selective oxidation re-
action of alcohol to aldehydes in water? In this article, we described
that complex 1 was employed to catalyze the oxidation of several
benzylic alcohols in aqueous solution and the resulting oxidation
products, benzaldehydes, could be isolated in good yields, which
represents an interesting example in the Cu(II)-catalyzed alcohol
oxidation reactions.
2
-Methoxybenzaldehyde (3b)
Colorless solid; yield: 258 mg, 95%; 1H NMR (400 MHz, CDCl
3
,
ppm): 10.45 (s, 1H), 7.80 (d, J ¼ 7.0 Hz, 1H), 7.53 (t, J ¼ 8.4 Hz, 1H),
d
13
6
d
3
.95e7.01 (m, 2H), 3.89 (s, 3H); C NMR (125 MHz, CDCl , ppm):
189.53, 161.10, 135.87, 128.19, 124.64, 120.46, 111.58, 55.46.
3
-Methoxybenzaldehyde (3c)
Light yellow oil; yield: 259 mg, 95%; H NMR (400 MHz, CDCl
1
3
,
ppm):
d 9.94 (s, 1H), 7.36e7.43 (m, 3H), 7.13e7.16 (m, 1H), 3.82 (s,
13
Experimental section
3H); C NMR (125 MHz, CDCl
3
, ppm): d 192.10, 160.15, 137.82,
130.04, 123.47, 121.45, 112.12, 55.45.
General procedures
4
-Methoxybenzaldehyde (3d)
Light yellow oil; yield: 264 mg, 97%; H NMR (400 MHz, CDCl
ppm):
9.73 (s, 1H), 7.69 (d, J ¼ 8.8 Hz, 2H), 6.86 (d, J ¼ 8.8 Hz, 2H),
.727 (s, 3H); C NMR (125 MHz, CDCl
31.72, 129.75, 114.13, 55.35.
All chemicals were purchased from commercial sources and
used without purification. Complex 1 was obtained according to
the published procedure [18]. The oxidation products were quan-
titatively analyzed by GC analysis using internal standards on an
Agilent 7820A Gas Chromatograph with an Agilent HP-5 chro-
1
3
,
d
13
3
1
3
, ppm): d 190.51, 164.41,
1
13
matographic column and N
2
as the mobile phase. The H and
C
2
-Methylbenzaldehyde (3e)
Colorless oil; yield: 211 mg, 88%; H NMR (400 MHz, CDCl
ppm):
10.26 (s, 1H), 7.79 (d, J ¼ 8.4 Hz, 1H), 7.47 (t, J ¼ 7.6 Hz, 1H),
.35 (t, J ¼ 7.6 Hz, 1H), 7.25 (d, J ¼ 7.6 Hz, 1H), 2.66 (s, 3H); C NMR
100 MHz, CDCl , ppm): 192.97, 140.77, 134.31, 133.80, 132.20,
131.92, 126.48, 19.74.
NMR spectra in CDCl or DMSO-d
3
6
were recorded at ambient
1
3
,
temperature on a Varian UNITYplus- 400 (400 MHz) spectrometer
and the chemical shifts were referenced to the TMS signal.
d
13
7
(
3
d
Typical procedure for the formation of aldehydes (3a-q)
A test tube equipped with a magnetic stirring bar was charged
with 1 (5 mg, 0.005 mmol, 0.25 mol%), TEMPO (16 mg, 0.10 mmol,
3
-Methylbenzaldehyde (3f)
Colorless oil; yield: 219 mg, 91%; 1H NMR (400 MHz, CDCl
3
,
5
2
2 3
mol%), and K CO (69 mg, 0.50 mmol, 25 mol%). Alcohols (2a-q,
ppm):
d
9.96 (s, 1H), 7.66 (s, 2H), 7.39 (t, J ¼ 7.6 Hz, 2H), 2.41 (s, 3H);
.0 mmol), H O (5 mL) and H
mixed light green solution was stirred at 60 C for 12 h, cooled to
2
2
O
2
(30%, 1 mL) were added. The
13
C NMR (100 MHz, CDCl
3
, ppm):
d
192.71, 139.05, 136.62, 135.41,
ꢀ
130.14, 129.00, 127.35, 21.31.
room temperature, and then extracted by Et
organic layers were combined, washed with brine (20 mL), dried
over anhydrous Na SO and concentrated under reduced pressure.
2
O (3 ꢁ 5 mL). The
4
-Methylbenzaldehyde (3g)
Colorless oil; yield: 224 mg, 93%; H NMR (400 MHz, CDCl
2
4
1
3
,
On elution with petroleum ether and ethyl acetate, the crude
product was further purified by column chromatography on silica.
All aldehyde products synthesized in this work are known and
ppm):
.44 (s, 3H); C NMR (100 MHz, CDCl
29.20, 128.04, 71.8, 21.32.
d
9.96 (s, 1H), 7.77 (d, J ¼ 8.0 Hz, 2H), 7.33 (d, J ¼ 8.0 Hz, 2H),
13
2
1
3
, ppm): d 137.41, 135.45,
1
confirmed by H NMR spectra.
4
-Chlorobenzaldehyde (3h)
Light yellow solid; yield: 213 mg, 76%; H NMR (400 MHz, CDCl
ppm):
9.99 (s, 1H), 7.83 (d, J ¼ 8.4 Hz, 2H), 7.53 (d, J ¼ 8.4 Hz, 2H);
C NMR (100 MHz, CDCl , ppm): 190.99, 141.09, 134.85, 131.04,
Benzaldehyde (3a)
1
3
,
Colorless oil; yield: 208 mg, 98%; 1H NMR (400 MHz, CDCl
,
3
d
ppm):
d
9.99 (s, 1H), 7.86 (d, J ¼ 7.2 Hz, 2H), 7.60 (t, J ¼ 7.6Hz, 1H),
13
3
d
129.60.
4
-Nitrobenzaldehyde (3i)
Light yellow solid; yield: 269 mg, 89%; 1H NMR (400 MHz,
CDCl
J ¼ 8.8 Hz, 2H); C NMR (100 MHz, CDCl
40.15, 130.58, 124.38.
3
, ppm):
d
10.17 (s, 1H), 8.41 (d, J ¼ 8.8 Hz, 2H), 8.09 (d,
13
3
, ppm): d 190.43, 151.20,
1
2
-Thiophenecarboxaldehyde (3j)
Light red oil; yield: 141 mg, 63%; 1H NMR (400 MHz, CDCl
ppm):
9.96 (d, J ¼ 1.2 Hz, 1H), 7.77e7.80 (m, 2H), 7.21e7.24 (m,
3
,
d
13
1
H); C NMR (125 MHz, CDCl
3
, ppm): d 182.95, 143.85, 136.42,
135.07, 128.31.
3
-Pyridinecarboxaldehyde (3k)
Colorless oil; yield: 156 mg, 73%; 1H NMR (400 MHz, CDCl
ppm):
10.19 (s, 1H), 9.13 (d, J ¼ 9.2 Hz, 1H), 8.89 (d, J ¼ 6.4 Hz,
H),8.23 (d, J ¼ 2.0 Hz, 1H), 7.54e7.56 (m, 1H); C NMR (100 MHz,
CDCl , ppm): 190.59, 154.31, 151.57, 135.58, 131.11, 123.82.
3
,
d
13
1
Scheme 1. Schematic representation of complex 1.
3
d
Please cite this article in press as: J. Gao, et al., Journal of Organometallic Chemistry (2015), http://dx.doi.org/10.1016/j.jorganchem.2015.02.008