Water → 1-(5-Bromopyridin-2-yl)-4-cyclopropylpiperazine

Participants

Reaction Steps

[(1-Ethoxy-cyclopropyl)oxy]trimethylsilane (26 mL, 129.3 mmol) was added to a solution of 1-(5-bromopyridin-2-yl)-piperazine (15 g, 62.0 mmol) in THF (120 mL). Water (24 mL), acetic acid (11 mL), and 1 M NaCNBH3 in THF (90 mL, 90 mmol) were added to the reaction mixture, which was then heated at reflux temperature for 3 hours. The resulting solution was cooled to rt and evaporated to dryness in vacuo. The residue was dissolved in a mixture of dichloromethane (200 mL) and water (50 mL) and 4 N sodium hydroxide (20 mL) was added to pH 8-9. The organic phase was isolated and the aqueous phase was extracted with further dichloromethane (100 mL). The combined organic phases were evaporated to dryness in vacuo and the residue was purified on a silica gel column (gradient: from 5% ethyl acetate in heptane to 100% ethyl acetate over 40 min.). This afforded 13.1 g (75%) of 1-(5-bromopyridin-2-yl)-4-cyclopropylpiperazine.

Provenance & Evidence