244
X. Zhang et al. / Journal of Organometallic Chemistry 749 (2014) 241e245
Table 3
the refrigerator for 24 h, the white crystal was obtained (436 mg,
70%). m.p 172e174 ꢀC; 1H NMR (400 MHz, [D6] acetone)
The Mannich reactions of aldehyde with amine and acetophenone catalyzed by 1a.a
d
¼ 6.58e
6.56 (m, 8H, Cp), 2.29 (s, 6H); 19F NMR (288 MHz, [D6]
acetone): ꢁ76.07 to ꢁ76.12 (m, 3F, CF3e), ꢁ109.49 to ꢁ110.55 (m,
2F, eCF2e), ꢁ115.50 to ꢁ115.55 (m, 2F, eCF2e), ꢁ116.59 to ꢁ116.88
(m, 6F, eCF2e), ꢁ117.71 to ꢁ117.75 (m, 2F, eCF2e), ꢁ121.18
to ꢁ121.20 (m, 2F,eCF2e).
Entry
R1
R2
Product (yield %)b
1
2
3
4
5
6
7
Ph
Ph
Ph
Ph
Ph
4a (96)
4b (95)
4c (98)
4d (98)
4e (98)
4f (98)
4g (96)
3.3. Typical procedure for FriedeleCrafts acylation of anisole (2a)
with acetic anhydride catalyzed by 1a
p-MeC6H4
p-ClC6H4
p-CF3C6H4
p-NO2C6H4
Ph
Ph
To a 10 mL sealed tube was added anisole (2a) (108 mg,
1.0 mmol), acetic anhydride (204 mg, 2.0 mmol) and catalyst 1a
(67.6 mg, 2.5 mol%). Then the mixture was stirred at room tem-
perature until complete consumption of starting material as
monitored by TLC or GCeMS analysis. Then the reaction mixture
was evaporated in vacuum, CH2Cl2 (3 ꢂ 10 mL was added to the
reaction mixture and the catalyst was filtered for the next cycle of
reaction. The combined CH2Cl2 solution was removed by evapora-
tion in vacuum and was then subject to silica gel column chro-
matograph. the FriedeleCrafts acylation product (3a) was obtained:
124 mg, isolated yield 83%.
p-MeC6H4
p-NO2C6H4
Ph
a
The mixture of R1CHO (1.0 mmol), R2NH2 (1.0 mmol), acetophenone (1.0 mmol),
catalyst (0.025 mmol) was stirred at room temperature for about 10 min.
b
The isolated yields.
(Table 3). It can be seen that the reaction for aromatic aldehydes
both with electron-donating and electron-withdrawing groups can
proceed fast to afford their corresponding products in high yields
(95e98%). These results demonstrate that complex 1a exhibits high
activity as a novel Lewis acid catalyst.
To test the reusability of the catalyst and the reproducibility of
catalytic performance, 1a was subjected to cycles of FriedeleCrafts
acylation of anisole (Table 4). The detected change in product yield
was minimal in a trial of five cycles, demonstrating that the catalyst
is stable and suitable for reuse.
3.4. Typical procedure for Mannich reaction of benzaldehyde with
amine and acetophenone catalyzed by 1a
To a 10 mL sealed tube was added catalyst 1a (67.6 mg, 2.5 mol
%), PhCHO (106 mg, 1.0 mmol), PhNH2 (93 mg, 1.0 mmol), and
acetophenone (120 mg, 1.0 mmol). Then the mixture was stirred at
room temperature for about 10 min until complete consumption of
starting material as monitored by TLC or GCeMS analysis. Then the
mixture was stirred at room temperature until complete con-
sumption of starting material as monitored by TLC or GCeMS
analysis. Then the reaction mixture was evaporated in vacuum,
CH2Cl2 (3 ꢂ 10 mL) was added to the reaction mixture and the
catalyst was filtered for the next cycle of reaction. The combined
CH2Cl2 solution was removed by evaporation in vacuum and was
then subject to silica gel column chromatograph. The Mannich re-
action product (4a) was obtained: 288 mg, isolated yield 96%.
3. Experimental
3.1. General
All reactions were carried out under nitrogen atmosphere with
freshly distilled solvents unless otherwise noted. THF was distilled
from sodium/benzophenone. Acetonitrile was distilled from CaH2.
Acetone was refluxed for 4 h and distilled with KMnO4, then dried
with K2CO3, after that, it was distilled, and kept in the dry box.
Conductivity was measured on REX conductivity meter DDS-307.
The crystal was mounted on a Bruker APEX area-detector diffrac-
tometer equipped with
a
graphite-monochromatic MoKa
4. Conclusions
ꢀ
(
l
¼ 0.71073 A) radiation. The structures were solved by direct
methods using the SHELXLS-97 program and refined by using the
SHELXL-97 program [19]. The complex 1a used in our catalytic
experiments was treated with the following processes: recrystal-
lization and vacuum treatment at 60 ꢀC for 1 h.
In conclusion, for the first time the novel air-stable Lewis acidic
binuclear complex of [{CH3CpZr(OH2)3}2(m
2-OH)2][OSO2C8F17]4$
2H2O$1THF$2(C3H6O) has been synthesized and its structure was
determined by single-crystal X-ray. The complex was characterized
by various techniques such as TG-DSC analysis, conductivity mea-
surement and acid strength (H0). It can be used as an excellent
catalyst for the FriedeleCrafts acylation of alkyl aryl ethers and the
Mannich reactions. The novel complex has the advantages of high
activity, selectivity, stability and reusability with better solubility
and competitive yields as compared to its counterparts, such as
Cp2Zr(OSO2C8F17)2.
3.2. Synthesis of complex 1a
To a solution of (CH3Cp)2ZrCl2 (0.16 g, 0.5 mmol) in 5 mL THF
was added a solution of AgOSO2C8F17 (0.605 g, 1 mmol) in 10 mL
THF. After the mixture was stirred at 25 ꢀC for 12 h in the absence of
light, it was filtrated. The filtrate was added into acetone and placed
in a small jar and then put into a larger jar which was added 20 mL
dry hexane and then the larger jar was obdurate. After keeping in
Acknowledgments
The authors thank the National Natural Science Foundation of
China (No 21172061 and 21273068), the NSF of Hunan Province
(10JJ1003, 11JJ5009), and the Fundamental Research Funds for the
Central Universities, Hunan university, for financial support.
Table 4
Yield of the FriedeleCrafts acylation of anisole with acetic anhydride catalyzed by
recovered 1a.a
Entry of cycle
1
2
3
4
5
Yield (%)b
Cat. (%)c
83
87
82
88
80
86
78
85
75
84
Appendix A. Supplementary material
a
Reaction conditions: anisole (1.0 mmol), Ac2O (2.0 mmol), 1a (2.5 mol %), rt.
Isolated yield of 4-methoxyl acetophenone.
Isolated yield of recovered catalyst.
b
c
CCDC 949982 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Zhang, Xiaohong
