Oxonium, trimethyl-, tetrafluoroborate(1-) (1:1) → 5-iodo-2-methyl-2H-indazole

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Reaction Steps

To a solution of 5-iodo-1H-indazole (500 g, 2.05 mol) in EtOAc (4 L) is added trimethyloxonium tetrafluoroborate (450 g, 3.04 mol). After the resulting white suspension is stirred at room temperature for 2 h, it is concentrated under vacuum. Ice water (1 L) is added to the residue, and it is basified to pH 12 with 10% aqueous NaOH solution. The solids are collected by filtration, and redissolved in DCM (5 L). The insolubles are filtered off and the filtrate is washed with 10% aqueous NaOH solution (2×100 mL). The organic layer is dried over anhydrous Na2SO4, filtered through a short silica gel column, and concentrated. Methyl tert-butyl ether is added to the residue to give a slurry and the product is collected by filtration to give the title compound (360 g, 68.0%). MS (m/z): 259.0 (M+H).

Provenance & Evidence