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. 2024 Oct 29;29(21):5112. doi: 10.3390/molecules29215112

Table 1.

Synthesis of 4a,5,8,8a-tetrahydro-1H-spiro[5,8-methanoquinazoline-2,3′-indoline]-2′,4(3H)-dione (3a).

graphic file with name molecules-29-05112-i001.jpg
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.