Hydroxide → HCID 117953181, compound

Participants

Reaction Steps

A 3-neck round-bottom flask (equipped with a mechanical stirrer, a heating mantle and reflux condenser) was charged with a one molar equivalent of 2,3-dimethylpiperidine in enough methanol to make a 0.5M concentration solution with respect to 2,3-dimethylpiperidine (note that the 2,3-dimethylpiperidine can be purchased directly from commercial sources or can be prepared by metal-catalyzed hydrogenation of 2,3-dimethylpyridine). To this solution, 1.5 molar equivalent of potassium bicarbonate was added. The solution was stirred for several minutes and then 2.5 molar equivalent of ethyl iodide was added dropwise via an addition funnel. Once the addition of ethyl iodide was completed, the reaction mixture was heated at reflux (about 55° C.) for several hours. The heat source was turned off and the reaction mixture was then stirred at room temperature for additional 48 hours. The progress of the reaction was monitored by NMR. Once completed, the reaction mixture was transferred to a recovery flask and the solvent removed on a rotary evaporator at reduced pressure. The obtained solids, a mixture of the product and potassium bicarbonate, were suspended in chloroform (500 mL CHCl3/1 mol 2,3-dimethylpiperidine). The resulting two-phase solution was filtered through a fritted-glass funnel. The filtrate containing the product (N,N-diethyl-2,3-dimethylpiperidinium iodide) was concentrated on a rotary evaporator at reduced pressure to give the desired salt as an off-white solid. The product was further purified by dissolving in a minimal amount of isopropyl alcohol and precipitating the product out by adding diethyl ether. The precipitate was filtered and dried on a rotary evaporator in a hot bath (70° C.) at reduced pressure to give the desired pure product in about 88% yield. The obtained N,N-diethyl-2,3-dimethylpiperidinium iodide was dissolved in deionized water (1 mL H2O/1 mmol salt) and then 1.1 g of hydroxide-based ion exchange resin/1 mmol salt was added. The resulting slurry was left to stir gently for a few hours. The slurry was filtered and the filtrate was analyzed by titration of a small aliquot with dilute HCl. The exchange afforded N,N-diethyl-2,3-dimethylpiperidinium hydroxide in nearly quantitative yield.

Provenance & Evidence