3
aldehyde to produce the corresponding radical E, which further
reacts with PINO to produce the N-hydroxyimide ester 3.
Table 2. Reaction of 2 with toluene derivatives.a
Entry
1
R
4-F
t (h)
12
12
12
36
16
12
16
16
16
16
40
24
24
24
24
3
3a
3b
3c
3d
3e
3f
Yield (%)b
63
60
59
43
48
50
51
53
50
56
40
73
68
58
54
2
4-Cl
3
4-Br
4
4-I
5
2-F
6
2-Cl
7
2,4-Cl
2-Br
3g
3h
3i
8
9
3-Br-4-F
3-Br
10
11
12
13
14
15
3j
4-NO2
4-OCH3
3-OCH3
2-OCH3
4-tBu
3k
3l
3m
3n
3o
Scheme 3. Proposed mechanism
Acknowledgment
aReactions were conducted with 1 (1.0 mmol), 2 (2.0 mmol) and
Fe(NO3)3·9H2O (20 mol%) in CH3CN (4 mL) at 70oC for 12–40
h under O2 (balloon) conditions. bIsolated yields based on 1.
We are grateful to the National Natural Science Foundation of
China (No. 21576239) for financial support. We thank Prof. Tao
Zhou at Zhejiang Gongshang University and Dr. Xinpeng Jiang at
Zhejiang University of Technology for helpful discussions.
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Scheme 2. Control experiment
In conclusion, we have developed a novel and efficient
method for the synthesis of N-hydroxyimide esters. This is the
first report that describes the use of toluene derivatives as the
coupling partners for NHPI to give the corresponding esters. In
addition, other advantages of this methodology include using
inexpensive Fe(NO3)3·9H2O as a radical initiator and O2 as an
oxidant. Further studies on the coupling reaction of amine with
N-hydroxyimide esters are underway.
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