3,4-dihydro-2H-pyran → 6-Bromo-4-nitro-2-(tetrahydro-2H-pyran-2-yl)-2H-indazole

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Reaction Steps

A mixture of 6-bromo-4-nitro-1H-indazole (available from Sinova, 10 g, 0.041 mol), 3,4-dihydro-2H-pyran (7.85 g, 8.52 ml, 0.093 mol) and pyridine 4-methylbenzenesulfonate (0.125 g, 0.496 mol) in dichloromethane (150 ml) was heated at reflux for 4.5 hours. The reaction was allowed to cool to room temperature and was poured onto saturated aqueous sodium bicarbonate (200 ml). The layers were separated and the aqueous layer extracted with dichloromethane (2×100 ml). The combined organic layers were washed with 5% aqueous citric acid (w/v, 100 ml) and brine (100 ml) and dried over magnesium sulphate. Solvent was removed in vacuo to give the title compound (12.9 g) as a dark orange solid.

Provenance & Evidence