3,4-dihydro-2H-pyran → 3-Bromo-1-(tetrahydro-2H-pyran-2-yl)-1H-indazole-5-carbonitrile

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Reaction Steps

To a solution of 13.67 g (61.56 mmol) of 3-bromo-1H-indazole-5-carbonitrile and 2.06 g (10.8 mmol, 0.175 equiv.) of p-toluenesulfonic acid monohydrate in 247 mL of anhydrous tetrahydrofuran (THF) was added 11.2 mL (123 mmol, 2.00 equiv.) of 3,4-dihydro-2H-pyran. The mixture was refluxed under a nitrogen atmosphere for 14 h. The reaction was quenched with saturated aqueous sodium bicarbonate (sat. aq. NaHCO3). The mixture was extracted twice with EtOAc. The combined organics were washed with 2× sat. aq. NaHCO3, 1× sat. aq. NaCl, and dried over Na2SO4. Chromatography of the crude material on 200 g of silica gel using 30% EtOAc in hexanes afforded the title compound (14.34 g, 76% yield): ES-MS (m/z) 306 [M+1]+.

Provenance & Evidence