3-Thiophen-2-ylpropan-1-amine hydrochloride → 3-(Thiophen-2-yl)propan-1-amine

Participants

Reaction Steps

A solution of 4.1 g of 3-(2-thienyl)propylamine (obtained from the hydrochloride by standard procedures) in about 100 ml of dimethylformamide was cooled to 0° C. and 5.7 g of solid 1,1'-thiocarbonyldiimidazole was added. The mixture was allowed to warm slowly to room temperature and then stirred for 16 hours. It was then poured into water and the resulting aqueous mixture was extracted with three portions of ethyl acetate. Saturated sodium chloride solution was added to break up any emulsion. The resulting ethyl acetate solution was washed with water, dried over sodium sulfate and then concentrated. The crude product obtained was mixed with 3.0 g of aminoacetaldehyde dimethyl acetal in 80 ml of dimethylformamide and heated at 80° C. for 3 hours. The mixture was then cooled to room temperature and the solvent was removed under reduced pressure. The residue was dissolved in ethanol and 2.5N hydrochloric acid was added to hydrolyze the acetal. The mixture was heated at reflux for 2 hours and then cooled to room temperature and poured into 500 g of ice. The resulting mixture was then heated to remove any remaining ethanol but no solid formed in the residual mixture which was then extracted with three portions of ethyl acetate. The ethyl acetate extracts were combined and dried over sodium sulfate and the solvent was evaporated to give a residual tan oil. This oil crystallized on standing and was recrystallized from toluene to give 1,3-dihydro-1-[3-(2-thienyl)propyl-2H-imidazole-2-thione melting at about 94°-96.5° C.

Provenance & Evidence