p-Toluenesulfonic acid → 3-Chloro-5-(1,3-dioxan-2-yl)-1H-indazole

Reaction equation

[Cl:1][C:2]1[C:10]2[C:5](=[CH:6][CH:7]=[C:8]([CH:11]=[O:12])[CH:9]=2)[NH:4][N:3]=1.[CH2:13](O)[CH2:14][CH2:15][OH:16].C1(C)C=CC(S(O)(=O)=O)=CC=1>C1(C)C=CC=CC=1>[Cl:1][C:2]1[C:10]2[C:5](=[CH:6][CH:7]=[C:8]([CH:11]3[O:16][CH2:15][CH2:14][CH2:13][O:12]3)[CH:9]=2)[NH:4][N:3]=1

Participants

Procedure

2.2 g (12.2 mmol) 3-chloro-1H-indazole-5-carbaldehyde (Example 43A), 4.64 g (60.9 mmol) propane-1,3-diol and a trace amount of p-toluene sulfonic acid in toluene (60 ml) were heated to reflux for 12 h using a Dean-Stark trap. After cooling, the mixture was concentrated under reduced pressure. The residue was dissolved in ethyl acetate and washed with water. The organic layer was dried with sodium sulfate, filtered and evaporated to dryness. The remaining solid (2.76 g, 91% of th.) was used in the next step without further purification.