Ring Opening and Expansion of Aziridines Using Silica-Water System

Significance

Ring opening and expansion of aziridines in a silica-water medium were demonstrated. Thus, reaction of aziridines 1a-g with potassium cyanide (KCN) in the presence of silica gel 60 in water gave the ring-opening products 2a-g in 24-88% yield (eq. 1). Silica gel can be recovered without any special treatment and reused three times without loss of reactivity. Aziridine 1a was treated with ZnI₂ in a silica-water medium to afford 3a in 90% yield along with its regioisomer 4a (6%) (eq. 2). Ring expansion of aziridine 1a with potassium thiocyanate (KSCN) in a silica-water medium afforded thiazoline derivative 5a in 80% yield (eq. 3).