Y.-M. Ren et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
3
t2:1
t2:2
t2:3
Table 2
oxathioacetals and dithioacetals in the presence of ketone functions in 131
multi-functional compounds. 132
Conversion of carbonyl compounds to oxathiolanes and dithioacetals catalyzed by
PEG1000-DAIL.
In addition, the PEG1000-DAIL could be typically recovered and 133
reused for subsequent reactions with no appreciable decrease in yield 134
and reaction rates (Table 1, entry 1). The recycling process involved 135
the upper layer of toluene containing products and was removed by 136
decantation, and the under layer of PEG1000-DAIL was concentrated to 137
remove generated water under reduced pressure. Fresh substrates 138
were then recharged to the residual PEG1000-DAIL, and the mixture 139
was heated to react once again, and only 4.0% loss of weight was ob- 140
t2:4
Entry
Carbonyl compounds
X
t (min)
Yield (%)a
93, 93, 93, 92, 92, 91, 90b
t2:5
1
2
3
4
5
6
7
8
Benzaldehyde
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S
S
S
S
S
S
S
S
S
8
6
8
10
15
18
10
12
8
t2:6
4-Methoxy-benzaldehyde
4-Methyl-benzaldehyde
2-Methyl-benzaldehyde
4-Nitro-benzaldehyde
2-Nitro-benzaldehyde
4-Chloro-benzaldehyde
2-Chloro-benzaldehyde
Butanal
Heptanal
Cyclopentanone
Cyclohexanone
Acetophenone
94
92
90
90
88
92
89
91
90
92
90
89
90
92
95
93
88
91
92
90
91
87
t2:7
t2:8
t2:9
t2:10
t2:11
t2:12
t2:13
t2:14
t2:15
t2:16
t2:17
t2:18
t2:19
t2:20
t2:21
t2:22
t2:23
t2:24
t2:25
t2:26
t2:27
served after recycling 7 times.
141
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
8
4. Conclusions
142
80
80
120
150
8
In conclusion, we have developed a simple, novel and effective meth- 143
Benzophenone
Benzaldehyde
od for the protection of carbonyl compounds catalyzed by PEG1000-DAIL. 144
The advantages of the present reaction are the elimination of the metals, 145
short reaction times, high chemoselectivity, operational simplicity and 146
good yields of products. Simple reaction conditions, good thermoregulat- 147
ed biphasic behavior of PEG1000-DAIL and facile manipulations in the 148
4-Methoxy-benzaldehyde
4-Methyl-benzaldehyde
4-Nitro-benzaldehyde
4-Chloro-benzaldehyde
Butanal
Heptanal
Cyclohexanone
Acetophenone
7
7
16
12
10
10
80
120
isolation of the product are the attractive features of this methodology. 149
OOF
Moreover, the excellent recyclability of the PEG1000-DAIL makes 150
this procedure cleaner, which is a good example of green chemistry 151
technology.
152
a
t2:28
t2:29
Isolated yields.
The PEG1000-DAIL was run for seven consecutive cycles.
b
Acknowledgments
153
PEG1000-DAIL.
The project is sponsored by the Anhui University for Young Elite 1Q 5 74
Talents (No. 2013RZR002ZD) and the National Innovation Program for 155
University Students (Nos. 201210363036 and 201310363065).
156
S
S
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157
CHO
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169
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172
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175
176
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180
181
182
[
[
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[
1
21
22
23
24
25
26
27
28
29
30
83
The differences of reactivities of the aldehydes and ketones suggest
1
that this method can be used for the selective protection of these groups,
and the high chemoselectivity of the method has also been demonstrated
by a competitive reaction between the acetal of an aldehyde and a
ketone. For instance, when an equimolar mixture of benzaldehyde
and acetophenone was allowed to react with ethane-1,2-dithiol using
PEG1000-DAIL as catalyst in toluene, only the 2-phenyl-1,3-oxathiolane
was obtained, acetophenone was recovered quantitatively (Scheme 3).
This indicates that the presented protocol is potentially applicable
for the chemoselective protection of aldehydes to the corresponding
1
1
[
[
[
1
1
1
[
[
[
1
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1
1
1
UNCORRECTED PR