1. Preparation of 1,1-dioxo-tetrahydro-thiophen-3-ylamine hydrochloride: 3-cyclobutylsulfone (compound 10a, 0.5 g, 4.2 mmol) was dissolved in 10 mL of 26% ammonia (NH4OH) in a sealed reaction tube and heated to react for 4 hours at 80°C. The reaction was carried out under reduced pressure. After completion of the reaction, the mixture was concentrated under reduced pressure to give a yellow oil. The oily material was dissolved in 3 mL of ethanol (EtOH) and acidified by slowly adding 1 mL of concentrated hydrochloric acid (HCl). The acidified mixture was stirred for 0.5 h. Subsequently, ether was added to promote crystallization of the hydrochloride. The solid product was collected by filtration, washed with ether and finally dried under vacuum to afford 1,1-dioxo-tetrahydro-thiophen-3-ylamine hydrochloride (Compound 10b, 0.533 g, 74% yield).
