Table 2.
Base and solvent screening.
|
Entry |
Amine |
Solvent |
Yield of 3 a [%][a] |
|---|---|---|---|
|
1 |
DABCO |
MeCN/THF 5:1 |
60 |
|
2 |
Et3N |
MeCN/THF 5:1 |
47 |
|
3 |
DIPEA |
MeCN/THF 5:1 |
44 |
|
4 |
quinuclidine |
MeCN/THF 5:1 |
19[b] |
|
5 |
pyridine |
MeCN/THF 5:1 |
36[b] |
|
6 |
DMAP |
MeCN/THF 5:1 |
8[b] |
|
7 |
NMePip |
MeCN/THF 5:1 |
64 |
|
8 |
NMePip |
MeCN |
41 |
|
9 |
NMePip |
Acetone |
>95 |
|
10 |
N MePip |
DMC |
>95 |
|
11 |
NMePip |
Acetone/DMC 1:1 |
95 |
[a] Determined by 19F qNMR spectroscopy with 3,3′‐bis(trifluoromethyl)benzophenone as internal standard. [b] Tritylated sulfonamide 3 aa was the main product. DIPEA=N,N‐diisopropylethylamine, DMAP=4‐dimethylaminopyridine, Pip=piperidine.