Water → HCID 11807407, compound

Participants

Reaction Steps

A solution of 1,4-cyclohexanedione monoethylene-ketal (50.0 g), 1-(2-pyridyl)piperazine (52.16 g), and p-toluenesulfonic acid (0.5 g) in 500 ml of toluene is refuxed with a Dean-Stark trap until the theoretical amount of water is collected (about four hours). The solvent is evaporated in vacuo and the residue is dissolved in 750 ml of methanol. This solution is cooled in an ice bath and sodium cyanoborohydride (30.1 g) is added in small portions over a two-minute period. The resulting suspension is stirred mechanically and over the next 30 minutes enough concentrated hydrochloric acid solution is added dropwise to the reaction mixture to maintain a pH of about 4. The solvent is removed in vacuo to leave a semisolid residue which is dissolved in 300 ml of a 10% solution of hydrochloric acid in a well ventilated fume hood. This solution is diluted with an equal volume of acetone and refluxed for two hours. The volatile components of the mixture are removed in vacuo and the residue is cooled in an ice bath and made basic with concentrated ammonium hydroxide. The white solid which forms is recrystallized from ethyl acetate-heptane to give 52.4 g of the title compound; mp 142°-144° C.

Provenance & Evidence