Table 2.
Cyclization of 8 in the presence of 1 mol % of activators and reference compounds.
|
Entry |
Activator[a] |
Yield[b] of 9 a/b [%] |
k rel [c] |
|---|---|---|---|
|
1 |
None |
≤5[d] |
‐ |
|
2 |
1 a |
76 |
740 |
|
3 |
1 b |
≤5 |
14 |
|
4 |
2 a |
43 |
420 |
|
5 |
2 b |
≤5 |
10 |
|
6 |
3 a |
≤5 |
1 |
|
7 |
3 b |
≤5 |
10 |
|
8 |
4 a |
83 |
830 |
|
9 |
4 b |
≤5 |
3 |
|
10 |
5 a |
≤5 |
41 |
|
11 |
NaBArF 4 |
84 |
850 |
|
12 |
TMABArF 4 |
≤5 |
5 |
[a] Activators added in 1 mol %. [b] 1H NMR yield of 9 a/b after 40 minutes of reaction time, unless indicated otherwise. An error margin of ≈5 % is assumed. All experiments were reproduced at least twice. [c] Relative initial rates after 20 minutes of reaction time, referenced to 3 a (and rounded to two valid digits). [d] 15 hours reaction time.