5-chloro-1-methyl-4-nitro-1H-pyrazole → 5-(3,4-dihydro-2H-pyran-6-yl)-1-methyl-4-nitro-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

A mixture of 5-chloro-1-methyl-4-nitro-1H-pyrazole (200 mg, 1.25 mmol), potassium fluoride dihydrate (235 mg, 2.5 mmol) and 3,4-dihydro-2H-pyran-6-boronic acid pinacol ester (394 mg, 1.88 mmol) in THF (3 mL) was degassed by bubbling nitrogen through it for 15 min. Tris(dibenzylideneacetone)dipalladium/tri-tert-butyl phosphonium tetrafluoroborate mixture (mole ratio: 1/1.2, 151 mg, 0.13 mmol) was added and the mixture degassed for a further 10 min before being heated in the microwave at 85° C. for 2 hr. Water (10 mL) was added and the mixture extracted with EtOAc (3×5 mL). The combined organic layers were passed through a phase separation cartridge and concentrated under reduced pressure. Purification via silica gel chromatography (0-5% EtOAc/isohexane) gave 5-(3,4-dihydro-2H-pyran-6-yl)-1-methyl-4-nitro-1H-pyrazole as a yellow solid (215 mg, 82%). 1H NMR (400 MHz, CDCl3) δ 8.04 (s, 1H), 5.22 (t, J=3.9 Hz, 1H), 4.20 (t, J=5.1 Hz, 2H), 3.88 (s, 3H), 2.31-2.24 (m, 2H), 2.05-1.96 (m, 2H).

Provenance & Evidence