General Method B: Deprotection of phthalimidosulfonamides to prepare the corresponding primary amines. The following procedure applies to the synthesis of aminoethanesulfonamides or aminopropanesulfonamides. The synthesis of 2-aminoethanesulfonamide hydrochloride from 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethanesulfonamide was carried out as follows: 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethanesulfonamide (1.52 g, 6.78 mmol) was suspended in ethanol (30 ml), and refluxed by heating. Subsequently, 64% hydrazine hydrate solution (0.36 ml, 7.5 mmol) was slowly added to the reaction system. After 3 hours of reaction, precipitate generation was observed and the precipitate was removed by filtration. The filtrate was concentrated to dryness and the residue was dissolved in water (150 ml). The aqueous phase suspension was acidified with concentrated hydrochloric acid and filtered to remove hydrochloric acid and insoluble impurities. The filtrate was again concentrated to dryness and the crude product was recrystallized by solvent mixing of ethanol/water (9:1) to give 764 mg (64% yield) of the target product 2-aminoethanesulfonamide hydrochloride as a solid. The product was characterized by 1H-NMR (D2O) with chemical shifts δ (ppm) of 3.62-3.55 (m, 2H) and 3.51-3.44 (m, 2H).
