Ethylamine → N-ethyl-3-chloro propylsulfonamide

To a solution of 3-chloropropylsulfonyl chloride 1(6.1 g,34.5mmol) in ether (25 ml) was added dropwise ethylamine (a 70% aqueous solution,4.4 g,68.3 mmol) with stirring under ice-cooling over 15 minutes. The resultant mixture was stirred for one hour at room temperature and concentrated in vacuo. Benzene (100 ml) was added to the residue and the solvent was distilled off in vacuo. To the residue was added ether (150 ml) and filtered to remove the insoluble material. The liltrate was distilled in vacuo to remove ether and 6.96 g (yield, about 100%) of crude N-ethyl-3-chloro propylsulfonamide (intermediate 3a) was obtained as colorless crystals (m.p.=30°-32° C.). To a solution of this intermediate 3a (6.96 g,34.5 mmol) in THF (50 ml) was slowly added sodium hydride (60% in oil,1.52 g,38.0 mmol) with stirring under ice-cooling over 15 minutes. The reaction mixture was stirred for another 30 minutes at room temperature. After the addition of ether (50 ml), the mixture was filtered to remove insoluble material and the filtrate was distilled in vacuo to remove solvent and to give 4.93 g (96%) of the objective compound 4a as a pale yellow oil.