Table 1.
Entry | Catalyst | Solvent | Temp. (°C) | Time (h) | Yield a (%) |
---|---|---|---|---|---|
1 | NH4Cl | EtOH | Rt b | 24 | 29 c |
2 | NH4Cl | EtOH | 78 | 12 | 37 c |
3 | NH4Cl | 2M2B d | 100 | 9 | 35 |
4 | LiOH | EtOH | Rt b | 72 | 10 |
5 | LiOH | EtOH | 78 | 72 | 21 |
6 | p-TsOH | EtOH | Rt b | 168 | – |
7 | p-TsOH | EtOH | 78 | 168 | – |
8 | Amberlyst 15 | EtOH | Rt b | 120 | 20 c |
9 | Amberlyst 15 | EtOH | 78 | 10 | 25 c |
10 | I2 | EtOH | Rt b | 215 | – |
11 | I2 | EtOH | 78 | 14 | 35 |
12 | Alum | Glycerol | Rt b | 168 | – |
13 | Alum | Glycerol | 100 | 5 | – |
14 | Alum | 2M2B d | Rt b | 72 | – |
15 | Alum | 2M2B d | 100 | 168 | – |
16 | Alum | EtOH | 78 | 5 | 42 |
17 | Alum | Water | rt | 168 | – e |
18 | Alum | Water | 100 | 8 | – e |
a Isolated yield after purification by flash chromatography. b Room temperature. c The reaction was not selective, since the product contained the mixture of two diastereomers according to the 1H-NMR spectrum. d 2M2B: 2-methyl-2-butanol. e The starting materials did not dissolve in water and there was no transformation.