p-Toluenesulfonic acid → 6-Bromo-1-(tetrahydro-pyran-2-yl)-1H-indazole-3-carbaldehyde

Participants

Reaction Conditions

Reaction Steps

To a solution of 6-bromo-1H-indazole-3-carbaldehyde (13.97 g, 61.9 mmol) in DCM (150 mL) was added p-TsOH (2.36 g, 12.4 mmol) and the mixture was cooled to 0° C. 3,4-Dihydro-2H-pyran (8.47 mL, 92.8 mmol) was added dropwise to the solution and the reaction was stirred at room temperature overnight. The reaction mixture was diluted with DCM (200 mL) and washed with a solution of saturated aqueous sodium hydrogen carbonate (500 mL). The aqueous layer was re-extracted with DCM (500 mL) and the combined organic layers were washed with brine (2×1 L), dried over MgSO4 and concentrated in vacuo to yield a black oil. The crude material was refluxed in cyclohexane (20 mL) and filtered while hot. The filtrate was concentrated in vacuo and the residue was stirred in heptane for 48 hours. The resulting solid was collected by filtration to give the title compound (13.87 g) in a 73% yield.

Provenance & Evidence