Table 1.
A comparison of CuAAC and metal‐free cycloaddition reactions.
|
|
Entry |
Catalytic system[a] |
Solvent[a] |
Product |
Yield[a] [%] |
|---|---|---|---|---|---|
|
CuI‐catalyzed |
1 |
CuSO4 ⋅5 H2O (20 mol %), sodium ascorbate (40 mol %) |
CH2Cl2/H2O (1:1) |
8 |
70 |
|
2 |
CuSO4 ⋅5 H2O (20 mol %), sodium ascorbate (40 mol %) |
CH2Cl2/H2O (1:1) |
10 |
35 |
|
|
3 |
CuSO4 ⋅5 H2O (20 mol %), sodium ascorbate (40 mol %) |
CH2Cl2/H2O (1:1) |
12 |
32 |
|
|
4 |
CuSO4 ⋅5 H2O (1 equiv), sodium ascorbate (4 equiv) |
H2O |
8 |
9 |
|
|
metal‐free click reaction |
5 |
DBU (1 equiv), malononitrile (1 equiv) |
DMSO |
8 |
43 |
|
6 |
DBU (1 equiv), malononitrile (1 equiv) |
DMSO |
10 |
30 |
|
|
7 |
DBU (1 equiv), malononitrile (1 equiv) |
DMSO |
12 |
36 |
|
|
8 |
DBU (1 equiv), malononitrile (1 equiv) |
H2O |
8 |
30 |
[a] Reaction conditions and product yields correspond to the reaction mechanism depicted in Scheme 2.